Han Zhu

A new class of Co9 S8 @MoS2 core-shell structures formed on carbon nanofibers composed of cubic Co9 S8 as cores and layered MoS2 as shells is described. The core-shell design of these nanostructures allows the advantages of MoS2 and Co9 S8 to be combined, serving as a bifunctional electrocatalyst for H2 and O2 evolution.

Abstract Iron–nitrogen–carbon (Fe–N–C) is hitherto considered as one of the most satisfactory alternatives to platinum for the oxygen reduction reaction (ORR). Major efforts currently are devoted to the identification and maximization of carbon‐enclosed FeN 4 moieties, which act as catalytically active centers. However, fine‐tuning of their intrinsic ORR activity remains a huge challenge. Herein, a twofold activity improvement of pristine Fe–N–C through introducing Ti 3 C 2 T x MXene as a support is realized. A series of spectroscopy and magnetic measurements reveal that the marriage of FeN 4 moiety and MXene can induce remarkable Fe 3d electron delocalization and spin‐state transition of Fe(II) ions. The lower local electron density and higher spin state of the Fe(II) centers greatly favor the Fe electron transfer, and lead to an easier oxygen adsorption and reduction on active FeN 4 sites, and thus an enhanced ORR activity. The optimized catalyst shows a two‐ and fivefold higher specific ORR activity than those of pristine catalyst and Pt/C, respectively, even exceeding most Fe–N–C catalysts ever reported. This work opens up a new pathway in the rational design of Fe–N–C catalysts, and reflects the critical influence of Fe 3d electron states in FeN 4 moiety supported on MXene in ORR catalysis.

Abstract Tuning surface strain is a new strategy for boosting catalytic activity to achieve sustainable energy supplies; however, correlating the surface strain with catalytic performance is scarce because such mechanistic studies strongly require the capability of tailoring surface strain on catalysts as precisely as possible. Herein, a conceptual strategy of precisely tuning tensile surface strain on Co 9 S 8 /MoS 2 core/shell nanocrystals for boosting the hydrogen evolution reaction (HER) activity by controlling the MoS 2 shell numbers is demonstrated. It is found that the tensile surface strain of Co 9 S 8 /MoS 2 core/shell nanocrystals can be precisely tuned from 3.5% to 0% by changing the MoS 2 shell layer from 5L to 1L, in which the strained Co 9 S 8 /1L MoS 2 (3.5%) exhibits the best HER performance with an overpotential of only 97 mV (10 mA cm −2 ) and a Tafel slope of 71 mV dec −1 . The density functional theory calculation reveals that the Co 9 S 8 /1L MoS 2 core/shell nanostructure yields the lowest hydrogen adsorption energy (∆ E H ) of −1.03 eV and transition state energy barrier (∆ E 2H* ) of 0.29 eV (MoS 2 , ∆ E H = −0.86 eV and ∆ E 2H* = 0.49 eV), which are the key in boosting HER activity by stabilizing the HER intermediate, seizing H ions, and releasing H 2 gas.

Silica nanotubes (SNTs) with controlled nanotubular structure were synthesized via an electrospinning and calcination process. In this regard, SNTs were found to be ideal adsorbents for Pb(II) removal with a higher adsorption capacity, and surface modification of the SNTs by sym-diphenylcarbazide (SD-SNTs) markedly enhanced the adsorption ability due to the chelating interaction between imino groups and Pb(II). The pH effect, kinetics, isotherms and adsorption mechanism of SNTs and SD-SNTs on Pb(II) adsorption were investigated and discussed detailedly. The adsorption capacity for Pb(II) removal was found to be significantly improved with the decrease of pH value. The Langmuir adsorption model agreed well with the experimental data. As for kinetic study, the adsorption onto SNTs and SD-SNTs could be fitted to pseudo-first-order and pseudo-second-order model, respectively. In addition, the as-prepared SNTs and SD-SNTs also exhibit high adsorption ability for Cd(II) and Co(II). The experimental results demonstrate that the SNTs and SD-SNTs are potential adsorbents and can be used effectively for the treatment of heavy-metal-ions-containing wastewater.

A novel method was established for the ratiometric fluorescence detection of Cu2+ and glutathione (GSH) by carbon quantum dots (CQDs), and it was fabricated through one-pot facile hydrothermal treatment using o-phenylenediamine (OPD) and citric acid as precursors. Based on the selective oxidation reaction of OPD with Cu2+, the detection strategy of Cu2+ was proposed using ratiometric fluorescence probe. The oxidation production (2,3-diaminophenazine) of OPD, obtained through the oxidation reaction of OPD and Cu2+, not only emerged a new emission peak at 562 nm, but also quenched the fluorescence of CQDs with maximum emission at 446 nm. The mechanism was Förster resonance energy transfer (FRET) between CQDs and 2,3-diaminophenazine (oxOPD). Furthermore, the oxidation reaction between Cu2+ and OPD could be inhibited when added GSH into the solution, which could prevent the fluorescence of CQDs being quenched. The sensing system showed high sensitivity toward Cu2+ and GSH in a range of 0.25–10.0 μmol L−1 and 1.0–80.0 μmol L−1 with a detection limit 0.076 μmol L−1 and 0.30 μmol L−1, respectively. Besides, the proposed method could apply to efficient quantification of Cu2+ and GSH in practical samples.

An electronegativity-dominant high-entropy atomic environment regulation strategy was developed to manipulate the electrocatalytic properties by tailoring the competitive adsorption sites in HEA NPs.

We reported a conceptual and experimental breakthrough in serving the nanoscale high-entropy alloy (HEA) as substrates to stabilize the active Ir with ultra-low loading by using Fe, Co, Ni and Ru as stabilizing structural elements. The ultra-small FeCoNiIrRu HEA nanoparticles were in situ synthesized in electrospun carbon nanofibers (CNFs), and it exhibited thermodynamic induced phase evolution, as revealed by in situ characterization. The FeCoNiIrRu/CNFs exhibit exciting oxygen evolution reaction (OER) activity with low overpotential of 241 mV at 10 mA cm−2 and high mass activity of 205 mA mg-1Ir+Ru. The hysteretic diffusion effect of HEA strongly inhibits the metal leaching and dissolution, leading to the excellent durability. The OER performance can be optimized by changing the metal compositions and calcination temperatures. In situ Raman spectra reveal the formation of OH and superoxo (OO) intermediates on HEA NP surfaces. Theoretically calculation indicate that the electron density redistribution in FeCoNiIrRu NPs occurs from low electronegative elements (Fe, Co, and Ni) to high electronegative ones (Ir, Ru) and it make the Ir more active to simultaneously promote the conversion of *OOH and generation of O2.

Rational synthesis of cost-effectiveness, ultra-stable and high-efficiency bifunctional oxygen catalysts are pivotal for Zn-air batteries. Herein, fine Co2P/FeCo nanoparticles (NPs) anchored on Mn, N, P-codoped bamboo-like carbon nanotubes (Co2P/FeCo/MnNP-BCNTs) are constructed in the coexistence of melamine, poly(4-vinylpyridine) and adenosine-5′-diphosphate disodium salt (ADP) by convenient pyrolysis and follow-up acid treatment. The as-prepared catalyst exhibits the higher onset potential (Eonset = 0.97 V vs. RHE) and half-wave potential (E1/2 = 0.88 V vs. RHE) for oxygen reduction reaction (ORR), coupled with excellent oxygen evolution reaction (OER) with the lower overpotential of 324 mV at 10 mA cm−2. Notably, the home-made Zn-air battery delivers the greater peak power density of 220 mW cm−2, together with the outstanding cycling stability. The excellent performances of Co2P/FeCo/MnNP-BCNTs catalyst are mainly attributed to the highly conductive carbon nanotubes and the synergistic effects between carbon nanotubes and Co2P/FeCo NPs. This work offers a novel strategy to explore advanced bifunctional oxygen catalysts for high-efficiency metal-air batteries.

Exploring high-performance and stable transition metal electrocatalysts is prerequisite for boosting overall water splitting efficiency. In this study, iron (Fe), manganese (Mn) co-doped three-dimensional (3D) Ni3S2 nanoflowers were in situ assembled by many inter-connected 2D nanosheets on nickel foam (NF) via hydrothermal and sulfuration treatment. By virtue of the introduced Fe and Mn elements and unique flower-like structures, the as-prepared catalyst displayed high activity and stability for oxygen evolution reaction (OER), coupled with a small Tafel slope (63.29 mV dec−1) and a low overpotential of 216 mV to reach the current density of 30 mA cm−2. This study would shed some lights for facile synthesis of exceptional OER catalyst by tailoring the electronic structure and doping transition metal(s).

Strain engineering in bimetallic alloy structures is of great interest in electrochemical CO2 reduction reactions (CO2RR), in which it simultaneously improves electrocatalytic activity and product selectivity by optimizing the binding properties of intermediates. However, a reliable synthetic strategy and systematic understanding of the strain effects in the CO2RR are still lacking. Herein, we report a strain relaxation strategy used to determine lattice strains in bimetal MNi alloys (M = Pd, Ag, and Au) and realize an outstanding CO2-to-CO Faradaic efficiency of 96.6% and show the outstanding activity and durability toward a Zn-CO2 battery. Molecular dynamics (MD) simulations predict that the relaxation of strained PdNi alloys (s-PdNi) is correlated with increases in synthesis temperature, and the high temperature activation energy drives complete atomic mixing of multiple metal atoms to allow for regulation of lattice strains. Density functional theory (DFT) calculations reveal that strain relaxation effectively improves CO2RR activity and selectivity by optimizing the formation energies of *COOH and *CO intermediates on s-PdNi alloy surfaces, as also verified by in situ spectroscopic investigations. This approach provides a promising approach for catalyst design, enabling independent optimization of formation energies of reaction intermediates to improve catalytic activity and selectivity simultaneously.

Abstract Achieving efficient efficiency and selectivity for the electroreduction of CO 2 to value‐added feedstocks has been challenging, due to the thermodynamic stability of CO 2 molecules and the competing hydrogen evolution reaction. Herein, a dual‐single‐atom catalyst consisting of atomically dispersed CuN 4 and NiN 4 bimetal sites is synthesized with electrospun carbon nanofibers (CuNi‐DSA/CNFs). Theoretical and experimental studies reveal the strong electron interactions induced by the electronegativity offset between the Cu and Ni atoms. The delicately averaged and compensated electronic structures result in an offset effect that optimizes the adsorption strength of the *COOH intermediate and boosts the CO 2 reduction reaction (CO 2 RR) kinetics, notably promoting the intrinsic activity and selectivity of the catalyst. The CuNi‐DSA/CNFs catalyst exhibits an outstanding FE CO of 99.6% across a broad potential window of −0.78– −1.18 V (vs the reversible hydrogen electrode), a high turnover frequency of 2870 h –1 , and excellent durability (25 h). Furthermore, an aqueous Zn‐CO 2 battery for CO 2 power conversion is constructed. This atomic‐level electronegativity offset of the dual‐atom structures provides an appealing direction to develop advanced electrocatalysts for the CO 2 RR.

Controlling atomic adjustment of single-atom catalysts (SACs) can directly change its local configuration, regulate the energy barrier of intermediates, and further optimize reaction pathways. Herein, we report an atom manipulating process to synthesize Ni atoms stabilized on vanadium carbide (NiSA-VC) through a nanofiber-medium thermodynamically driven atomic migration strategy. Experimental and theoretical results systematically reveal the tunable migration pathway of Ni atom from Ni nanoparticles to neighboring N-doped carbon (NC) and finally to metal carbide that was obtained by regulating the competitive adsorption energies between VC and NC for capturing Ni atoms. For CO2-to-CO electroreduction, NiSA-VC exhibits an industrial current density of -180 mA cm-2 at -1.0 V vs reversible hydrogen electrode and the highest Faradaic efficiency for CO production (FECO) of 96.8% at -0.4 V vs RHE in a flow cell. Significant electron transfers occurring in NiSA-VC structures contribute to the activation of CO2, facilitate the reaction free energy, regulate *CO desorption as the rate-determining step, and promote the activity and selectivity. This study provides an understanding on how to design powerful SACs for electrocatalysis.

Ultrathin and super-toughness gel polymer electrolytes (GPEs) are the key enabling technology for durable, safe, and high-energy density solid-state lithium metal batteries (SSLMBs) but extremely challenging. However, GPEs with limited uniformity and continuity exhibit an uneven Li+ flux distribution, leading to nonuniform deposition. Herein, a fiber patterning strategy for developing and engineering ultrathin (16 µm) fibrous GPEs with high ionic conductivity (≈0.4 mS cm-1 ) and superior mechanical toughness (≈613%) for durable and safe SSLMBs is proposed. The special patterned structure provides fast Li+ transport channels and tailoring solvation structure of traditional LiPF6 -based carbonate electrolyte, enabling rapid ionic transfer kinetics and uniform Li+ flux, and boosting stability against Li anodes, thus realizing ultralong Li plating/stripping in the symmetrical cell over 3000 h at 1.0 mA cm-2 , 1.0 mAh cm-2 . Moreover, the SSLMBs with high LiFePO4 loading of 10.58 mg cm-2 deliver ultralong stable cycling life over 1570 cycles at 1.0 C with 92.5% capacity retention and excellent rate capacity of 129.8 mAh g-1 at 5.0 C with a cut-off voltage of 4.2 V (100% depth-of-discharge). Patterned GPEs systems are powerful strategies for producing durable and safe SSLMBs.

FeCoNiMoRu/CNFs exhibits a small potential of 1.43 V vs. RHE (100 mA cm-2) and superior stability for 90 h toward urea electro-oxidation (UOR). In situ electrochemical Raman results strongly demonstrate the ensemble effects of the various metal sites on improving the UOR activity by co-stabilizing the important intermediates. This work will open new directions in the application of high-entropy alloys for small molecule oxidation reactions.

Covalent organic frameworks (COFs) are promising platforms with tailorable structures toward metal-free electrocatalytic oxygen reduction (ORR). Here, COFs with different linkages were constructed and explored in the selective two-electron ORR (2e- ORR) for hydrogen peroxide (H2O2) production. Interestingly, imine-linked Py-TD-COF delivers a remarkable H2O2 selectivity of 80–92 %, while amine-linked Py-TD-COF-NH exhibits relatively low H2O2 selectivity of 50–61 %. Experimental and theoretical results reveal that the donor-accepter property of Py-TD-COF enables proper activation of O2, while Py-TD-COF-NH shows relatively high activation of O2 due to the electronic modulation induced by the linkage transformation. Furthermore, the potential H-bonding between the amine group and the adsorbed oxygen molecules on Py-TD-COF-NH is proved to elongate the OO bond, thus accelerating the subsequent hydrogenation and lowering the barrier for the reduction of *OOH to *O intermediates. This work highlights the importance of suitable linkages and provides a guideline for designing metal-free COF catalysts for 2e- ORR.

A facile and green route was introduced to synthesize Au nanoparticles immobilized on halloysite nanotubes (AuNPs/HNTs) used for surface-enhanced Raman scattering substrates. The naturally occurring HNTs were firstly functionalized with a large amount of -NH(2) groups by N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane (AEAPTES), which possesses one lone electron pair and will "anchor" Au ions to form a chelate complex. Then, with the addition of tea polyphenols (TP), the Au ions were reduced on the surface of the previously formed Au-NH(2) chelate complex to form AuNPs. Transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM) observations indicate that a large amount of AuNPs were synthesized on HNTs. The AuNPs are irregularly spherical and densely dispersed on HNTs and the diameter of the nanoparticles varies from 20 to 40 nm. The interactions between AuNPs and -NH(2) groups were verified by X-ray photoelectron spectroscopy (XPS) and the results showed that the functional groups can "anchor" AuNPs through the chelating effect. The as-prepared AuNPs/HNTs nanomaterials with several nanometers gaps among nanoparticles were used as a unique surface-enhanced Raman scattering substrate, which possessed strong and distinctive Raman signals for R6G, indicating the remarkable enhancement effect of the AuNPs/HNTs.

The search for non-noble metal catalysts with high activity for the hydrogen evolution reaction (HER) is crucial for efficient hydrogen production at low cost and on a large scale. Herein, we report a novel WO3–x catalyst synthesized on carbon nanofiber mats (CFMs) by electrospinning and followed by a carbonization process in a tubal furnace. The morphology and composition of the catalysts were tailored via a simple method, and the hybrid catalyst mats were used directly as cathodes to investigate their HER performance. Notably, the as-prepared catalysts exhibit substantially enhanced activity for the HER, demonstrating a small overpotential, a high exchange current density, and a large cathodic current density. The remarkable electrocatalytic performances result from the poor crystallinity of WO3–x, the high electrical conductivity of WO3–x, and the use of electrospun CNFs. The present work outlines a straightforward approach for the synthesis of transition metal oxide (TMO)-based carbon nanofiber mats with promising applications for the HER.

S-rich MoS2–NCNF hybrid nanomaterials exhibiting extraordinary HER activity, with a very low onset potential of 30 mV and a small Tafel slope of 38 mV per decade, were successfully fabricated by combining N-doped carbon nanofibers and single-layered MoS2 nanostructures with abundant edge active sites.

Triangular W(Se_xS_1−x)₂ nanoflakes uniformly dispersed on the surface of electrospun carbon nanofiber mats were synthesized. The hybrid catalyst mats were directly used as hydrogen evolution cathodes and exhibit excellent HER performances.

An effective strategy for the rational design of 3D architectures for superior electrocatalysis, through the integration of CNFs, CNTs and oxygen-deficient Mn₃Co₇–Co₂Mn₃O₈ nanoparticles, has been demonstrated.

Two-dimensional MoS2 nanoplates within carbon nanofibers (CNFs) with monolayer thickness, nanometer-scale dimensions and abundant edges are fabricated. This strategy provides a well-defined pathway for the precise design of MoS2 nanomaterials, offering control over the evolution of MoS2 morphology from nanoparticles to nanoplates as well as from mono- to several-layer structures, over a lateral dimension range of 5 to 70 nm. CNFs play an important role in confining the growth of MoS2 nanoplates, leading to increases in the amount of exposed edge sites while hindering the stacking and aggregation of MoS2 layers, and accelerating electron transfer. The controlled growth of MoS2 nanoplates embedded in CNFs is leveraged to demonstrate structure-dependent catalytic activity in the hydrogen evolution reaction (HER). The results suggest that increases in the number of layers and the lateral dimension result in a decrease in HER activity as a general rule. Single-layer MoS2 nanoplates with abundant edges and a lateral dimension of 7.3 nm demonstrated the lowest hydrogen evolution reaction overpotential of 93 mV (J = 10 mA/cm2), the highest current density of 80.3 mA/cm2 at η = 300 mV and the smallest Tafel slope of 42 mV/decade. The ability of MoS2–CNFs hybrids to act as nonprecious metal catalysts indicates their promise for use in energy-related electrocatalytic applications.

A well-dispersed Au nanoparticle grown on carbon nanofibers (AuNPs/CNFs) with excellent electroanalytical activity and sensitivity towards the detection of heavy metal ions was synthesized via electrospinning technology and in situ thermal reduction. Field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) images show that a large amount of AuNPs with a diameter of 5–15 nm was homogenously distributed on the surface of the nanofibers. The AuNPs/CNFs hybrids modified electrode was utilized as the working electrode for the simultaneous detection of heavy metal ions such as Cd2+, Pb2+ and Cu2+ through the square wave anodic stripping voltammetry (SWASV) method. The electrochemical results indicate that the simultaneous detection of Cd2+, Pb2+ and Cu2+ with a low concentration of 0.1 μM can be obtained. This work may provide an easy way to construct electrochemical sensors for the quick detection of trace heavy metal ions.

PtCo/CNFs exhibit extraordinary catalytic activity and durability for hydrogen evolution reaction, even approaching the performance of the commercial Pt/C catalyst, which can be attributed to the alloy structure and the encapsulation of PtCo alloy nanoparticles in CNFs.

Hydrogen evolution reaction (HER) is regarded as a feasible strategy for producing high-purity hydrogen from abundant water. It is significant yet challenging for synthesis of Pt-based pH-universal HER electrocatalysts by substantially reducing the Pt loading without any decay in the activity. Herein, bimetallic PtRh alloyed dendritic nanoassemblies (DNAs) were efficiently prepared by a facile one-pot solvothermal strategy in oleylamine (OAm), coupling with the aid of glycine and cetyltrimethylammonium chloride (CTAC). By virtue of the unique branch-like structures and compositions advantages, the PtRh DNAs catalyst showed steeply enhanced HER activity with small overpotentials (i.e. 28 mV in 1.0 M KOH, 23 mV in 1.0 M phosphate buffer solution and 27 mV in 0.5 M H2SO4) at the current density of 10 mA cm−2, surpassing those of commercial Pt/C under such conditions. This work provides a facile and rational strategy to construct advanced Pt-based bimetallic electrocatalyst for energy-correlated applications.

3D dendritic WSe₂ on conductive carbon nanofiber mats (d-WSe₂/CFM) was synthesized and directly used as a hydrogen evolution cathode.

Electrode materials of flexible asymmetric supercapacitors are usually suffers from low capacitance and sluggish kinetics.

Alkaline hydrogen evolution reaction (HER) electrocatalysts with high catalytic activity and long-term durability are of significance for sustainable energy applications. Herein, we prepared trimetallic PtNiCo hollow alloyed 3D multipods (HAMPs) with rough surfaces by an effective one-pot solvothermal strategy coupled with acid etching, as evidenced by a series of characterizations. By virtue of the trimetals and unique structures, the PtNiCo HAMPs exhibited excellent HER performance in 1.0 M KOH electrolyte with a low overpotential (η, 20 mV) and small Tafel slope (46.3 mV dec−1), superior to homemade PtNi HAMPs, PtCo nanocrystals (NCs) and commercial Pt/C catalysts. This study provides some constructive guidelines for synthesis of advanced hollow multimetallic catalysts in energy systems.

The multicomponent combinations of metals in nanoscale high‐entropy materials (HEMs) have unique structure and physical and chemical properties, which provide them tailorable active sites and catalytic performance and attract intensive researches in recent years. Herein, an overview of the development of the synthesis strategies for various types of HEMs and their formation mechanisms is provided. These synthesis methods are compared, and their advantages and challenges are illustrated. The superior catalytic behavior of HEMs compared with their traditional analogue materials in heterogeneous catalysis are discussed and the underlying structure–activity correlation is revealed. The perspectives for future HEMs design are provided to achieve significant progress for catalytic applications.

Shaped-controlled synthesis of high-efficiency electrocatalysts towards ethanol oxidation reaction (EOR) and ethylene glycol oxidation reaction (EGOR) is important for development of alcohol alkaline fuel cells. Herein, one-step aqueous method was developed for constructing hierarchically multi-branched PdRuCu nanoassemblies (NAs) under the guidance of octylphenoxypolyethoxyethanol (NP-40) and NaBr. The as-obtained PdRuCu NAs exhibited dramatically enhanced electrocatalytic activity and improved stability for EOR and EGOR in alkaline solution. The mass/specific activity of the as-prepared catalysts for EOR (1.16 A mg−1Pd/3.78 mA cm−2) and EGOR (1.29 A mg−1Pd/4.19 mA cm−2) were steeply higher than those of commercial Pd black (0.17 A mg−1Pd/1.81 mA cm−2; 0.21 A mg−1Pd/2.27 mA cm−2), respectively. This work would provide some valuable insights for synthesis of advanced polymetallic electrocatalysts in fuel cells.

Nitrite has been widely existed in food and natural environment systems. To protect the environmental safety and human health, non-enzymatic nitrite sensor with reasonable linear response range, low detection limit (LOD) and excellent storage stability are highly desirable. Herein, we designed a hierarchical structure including the multiwalled carbon nanotube (MWCNT) as substrates, Co-based metal-organic framework (Co-MOF) and high-dispersed small Au nanoparticles (AuNPs) (denoted as AuNPs/Co-MOF/MWCNT). Small Co-MOF nanoplates were firstly grown on the surface of MWCNT, and then provides abundant adsorption sites for catching Au ions. The Co-MOF plays a crucial role in controlling the growth and dispersion of AuNPs, and limits particle growth during the reduction process. Combining MWCNT with Co-MOF can significantly improve the electron transport capability of Co-MOF. On the other hand, small and uniform AuNPs distributed on Co-MOF can reduce the operating voltage and significantly enhance their catalytic activity for nitrite oxidation. Owing to the intriguing synergy between the components, the obtained nitrite sensor device exhibits a broad linear response range from 1 to 1000 µM and a LOD of 0.4 µM (S/N = 3) with a fast response balance (the response time ≈ 3.5 s) at a voltage of 0.72 V. Moreover, this sensor remains 94.5% of their initial response after 20 days of storage at room temperature in air. These results suggested that the AuNPs/Co-MOF/MWCNT nanocomposite has a good application prospect in the amperometric determination of nitrite.

It is still of great challenge to develop green and efficient electrochemical sensors for detection of trace heavy metal ions. In this work, an efficient method was demonstrated for fabricating Palladium nanoparticles (Pd NPs) uniformly decorated porous activated carbon (PAC). The Pd NPs were in-situ reduced on PAC ([email protected]) via a KOH activation and thermal reduction method. The morphology investigation suggests that the [email protected] possess typical interconnected micropores and mesopores architecture with Pd NPs evenly dispersed on the surface of PAC. The [email protected] modified glassy carbon electrode ([email protected]/GCE) was used for the detection of trace Cd2+, Pb2+ and Cu2+ ions by square wave anodic stripping voltammetry (SWASV). It exhibited excellent sensitive and selective detection of heavy metal ions simultaneously and individually, together with good anti-interference, reproducibility, repeatability and stability under the same experimental conditions. Moreover, the [email protected]/GCE was utilized to detect heavy metal ions in real sample species, indicating potential application in real environment detection. Porous structure and Pd NPs make [email protected] excellent electrochemical activity, its interconnected micropores and mesopores architecture accelerate the mass diffusion and facilitate the deposition-stripping process of heavy metal ions. Pd NPs provide more active sites and improved conductivity significantly. The present investigation provides a green and feasible method to assemble efficient electrochemical sensors and electrocatalytic devices.

We proposed a conceptual and experimental breakthrough in overcoming the high energy barriers for N 2 absorption and activation by tuning the center positions of pz orbital of boron in S and B co-doped carbon nanofibers (S-B/CNFs). • CNFs were used as nanoreactor to synthesize B, S co-doped carbon materials. • Results investigated the influences of B, S, P as electron donor on tuning their NRR activity. • S 6.23 -B 8.09 /CNFs exhibits excellent NRR activity with FE of 22.4 % and NH 3 yield of 0.223 μmol h −1 cm -2 at −0.7 V. • S, B doping facilitates the adsorption of N 2 and reduces the energy barriers for rate-determining steps. Herein, we proposed a conceptual and experimental breakthrough in overcoming the high energy barriers for N 2 absorption and activation by tuning the center positions of p z orbital of boron in S and B co-doped carbon nanofibers (S-B/CNFs). We theoretically and experimentally investigated the influences of nonmetallic elements of B as electron acceptor, and S and P as electron donor on tuning NRR activity. We revealed that the heteroatom-doping of S atoms induced changing of center position of the p z orbital of B facilitates the adsorption of N 2 on S-C-B sites and reduces the energy barriers for rate-determining steps. The S 6.23 -B 8.09 /CNFs exhibits the highest NRR activity with high Faradaic efficiency of 22.4 % and NH 3 yield of 0.223 μmol h −1 cm -2 at −0.7 V versus reversible hydrogen electrode. The combined computational and experimental works uncover the relationship between the p -band center of heteroatom doped carbon catalysts and NRR activity.

Reasonable design of heterojunctions is considered to be an effective way to construct highly efficient photocatalysts. In this work, Bi2S3/BiFeO3 heterojunction nanofibers with tightly integrated interface were prepared by electrospinning technique and in-situ anion exchange method. Various characterizations were conducted to analyze the structure and morphology of Bi2S3/BiFeO3 composites. The photocatalytic activities of the obtained Bi2S3/BiFeO3 heterojunctions were evaluated by photodegradation of tetracycline hydrochloride (TC) under visible light irradiation. It can be found that Bi2S3/BiFeO3 heterojunctions showed enhanced photocatalytic degradation performance, and their photocatalytic activities can be easily optimized by changing the amount of thioacetamide (TAA). When the amount of TAA was 0.1 mmol, the obtained Bi2S3/BiFeO3 (TAA-2) sample exhibited the best photocatalytic performance, which was 5 and 6 times of pure BiFeO3 and Bi2S3, respectively. Besides, the photocatalytic mechanism was systematically studied by monitoring the active species and radicals, and by performing the optical and photoelectrochemical tests. Accordingly, a direct Z-scheme charge migration mechanism for Bi2S3/BiFeO3 heterojunctions was proposed. The enhanced photocatalytic performance of Bi2S3/BiFeO3 heterojunctions can be attributed to the improved visible light response and efficient charge separation and transfer.

Engineering the morphology and electronic properties simultaneously of emerging metallene materials is an effective strategy for enhancing their performance as oxygen reduction reaction (ORR) electrocatalysts. Herein, a highly efficient and stable ORR electrocatalyst, Fe-doped ultrathin porous Pd metallene (Fe-Pd UPM) composed of a few layers of 2D atomic metallene layers, was synthesized using a simple one pot wet-chemical method and characterized. Fe-Pd UPM was measured to have enhanced ORR activity compared to undoped Pd metallene. Fe-Pd UPM exhibits a mass activity of 0.736 A mgPd-1 with a loss of mass activity of only 5.1% after 10 000 cycles at 0.9 V versus the reversible hydrogen electrode (vs RHE) in 0.1 M KOH solution. Density functional theory (DFT) calculations reveal that the stable Fe dopant in the inner atomic layers of Fe-Pd UPM delivers a much smaller overpotential during O* hydrogenation into OH*. The morphology, porous structure, and Fe doping were verified to have enhanced ORR activity. We believe that the rational design of metallene materials with porous structures and interlayer doping is promising for the development of efficient and stable electrocatalysts.

The challenges for preparing metal single atoms (MSAs) catalysts are facile synthesis approaches and the suitable supports with strong coordination to stabilize MSAs. Herein, we reported a facile strategy to synthesize the Ru single atoms (Ru SAs) through the dynamic transformation from clusters to single atoms by combining the electrospun technology and NH3-assisted graphitization process. The small Ru nanoclusters (NCs) supported on carbon nanofibers (CNFs) were in situ converted into Ru SAs in N-doped CNFs under the NH3 treatment. Through controlling the NH3 treatment time and graphitization temperatures, the Ru nanocrystals exhibit a dynamic transformation from nanoclusters to single atoms. The results indicate that the Ru NCs with larger amounts of Ru SAs exhibit superior HER activity in alkaline media with low overpotential of 34 mV at 20 mA cm−2, which is even significantly better than commercial Pt/C catalysts. The mass activity of Ru SAs/NCNFs is about 390 A g−1Ru at an overpotential of 100 mV, which is ~3.5 times higher than that of commercial Pt/C (110 A g−1Pt). This strategy will provide a new way for the large-scale production of MSAs transformed from different metal nanoparticles or nanoclusters.

Abstract The electrochemical N 2 reduction reaction (eNRR) is considered to be an attractive alternative to overcome the short‐comings of the Haber‐Bosch method, where the electrocatalysts play a vital role in the eNRR efficiency. Herein, isolated single‐B sites with electron deficiency in intermetallic carbide are rationally designed to trigger charge density redistribution, achieving excellent selectivity for eNRR. The B‐rich VC nanocrystals are in situ synthesized on carbon nanofibers (B‐VC/CNFs), and the ordered intermetallic structure of VC can isolate contiguous B atoms into single‐B sites with specific electronic structures. In light of density functional theory calculations, the as‐designed BCV configuration can regulate the adsorption behavior of N 2 and decrease the energy barrier for the proton–electron coupling and transferring process (*NN → *NNH), endowing the distinguished activity and selectivity, as evidenced by excellent Faradaic efficiency of 46.1% and NH 3 yield of 0.443 µmol h –1 cm –2 . The operando Raman spectra reveals the formation of NH intermediates on the surfaces of B‐VC/CNFs, further confirming the calculated eNRR pathway. This intermetallic carbide host strategy for generating electron‐deficient single‐B sites offers powerful guidelines for designing advanced eNRR electrocatalysts to achieve effective ammonia production.

Designing bimetallic electrocatalysts with homogenous element distribution and tunable electronic structure is attractive strategy to enhance the CO selectivity in electrochemical carbon dioxide reduction reaction (CO2RR). Herein, we report a concept of atom-polymer hybridization to synthesize AuNi homogeneous solid-solution alloy nanoparticles (NPs) with positively charged Ni center supported on electrospun carbon nanofibers (CNFs). The nanofibers host can strong restrict the separated growth of Au and Ni nanoclusters during the directly graphitization process, leading to the formation of homogeneous AuNi alloy. In-situ characterizations reveal the formation process and phase evolution of the AuNi alloy during the carbonization. The positively charged Ni when alloying with Au lead to the enhanced local electronic structure on AuNi homogeneous solid-solution alloy due to the electron-withdrawal effect of nearby Au atoms. The AuNi homogeneous solid-solution alloy exhibits a high CO selectivity with an optimal CO Faradaic efficiency (FECO) of 92% at −0.98 V (vs. RHE). Theoretical calculations indicate that the incorporation of Ni into Au can make the d-band center more positive and reduce the free energy barrier for the CO2 activation into *COOH and *CO desorption. Operando Raman spectroscopy provides the evidences that AuNi homogeneous solid-solution alloy can facilitate the activation of CO2 into *COOH and enhance the interaction between *COOH and AuNi (1 1 1) due to the change of electronic structure.

Phthalocyanine (Pc), an electro-redox active moiety, has many attractive properties stemming from its large aromatic system and ability to act as a catalyst in electrochemical reactions, such as the CO2 reduction reaction (CO2RR). However, due to the synthetic challenge related to geometric requirements and poor solubility (strong aggregation), discrete shape-persistent cages consisting of site-isolated, readily accessible Pc moieties have not been available. Here, we report the synthesis of Zn- and Ni-metallated Pc-based molecular cages via one-step dynamic spiroborate linkage formation in high yields. The ZnPc cage structure is unambiguously elucidated at the atomic level by single-crystal X-ray diffraction. Moreover, owing to the site-isolated redox-active metal centers, readily accessible intrinsic cavity, and shape-persistent backbone, the Ni-metallated Pc (NiPc) cage exhibits high catalytic efficiency, selectivity, and stability, superior to the non-caged control molecules in electrocatalytic CO2RR.

Tuning the electronic property of active center to balance the adsorption ability and reactivity of oxygen is essential for achieving 2e − oxygen reduction reaction (ORR) for electrocatalytic synthesis of hydrogen peroxide (H 2 O 2 ), still represents a grand challenge. Herein, different by‐design building blocks are introduced to regulate the electronic structure of catalytically active centers in covalent organic frameworks (COFs). Theoretical calculation reveals that adsorption ability of oxygen molecule (O 2 ) can be finely tuned by the regulation of electronic structure and the binding strength of O 2 is positively correlated with the electron donating ability of active center. As a result, the newly designed TP‐TD‐COF shows higher 2e − ORR activity and selectivity owing to the stronger electron donating ability and the higher adsorption strength of O 2 on electron‐rich active center. This study reveals fundamental structure – activity relationship in H 2 O 2 synthesis and offers a strategy for designing metal‐free COF catalysts through rational modulation of their electronic properties at molecular level.

The conversion of organic compounds by photocatalysis under mild conditions is an environment-friendly alternative for organic transformations. In this work, the bimetallic covalent organic framework coordinated by Sr2+ and Fe2+ in the porphyrin centers with molar ratio of 2:1 (COF-Sr2Fe1) was synthesized through a two-step reaction. Under the synergistic regulation of Sr2+ and Fe2+, the separation of photogenerated charges and visible light absorption for COF-Sr2Fe1 were significantly promoted, and thus COF-Sr2Fe1 exhibited efficient photocatalytic performance towards benzylamine oxidative coupling reaction with a yield of 97 %, much higher than that of the nonmetallic covalent organic framework COF-366. Moreover, it was found that the Fe site displayed higher dehydrogenation ability and the Sr site displayed higher CN coupling ability through the density functional theory (DFT) calculations, thereby making the dehydrogenation and CN coupling steps more controllable for benzylamine oxidative coupling reaction by COF-Sr2Fe1. This work provides a strategy for designing efficient covalent organic frameworks photocatalysts, and helps to understand the oxidative coupling of amines more deeply.

Bisphenol A (BPA) was reported to show potential detrimental effects on wildlife and humans through altering endocrine function. In this study, a novel electrochemical imprinted sensor for sensitive and convenient determination of BPA was developed. Multi-walled carbon nanotubes (MWCNTs) and gold nanoparticles (GNPs) were introduced for the enhancement of electronic transmission and sensitivity. Thin film of molecularly imprinted sol–gel polymers with specific binding sites for BPA was cast on gold electrode by electrochemical deposition. The resulting composites were characterized by cyclic voltammetry (CV) and UV–visible spectra. Rebinding experiments were carried out to determine the specific binding capacity and selective recognition of the sensor. The linear range was from 1.13 × 10−7 to 8.21 × 10−3 mol L−1, with the limit of detection (LOD) of 3.6 × 10−9 mol L−1 (S/N = 3). The imprinted sensor was successfully tested to detect BPA in real samples.

A novel sensitive molecularly imprinted electrochemical sensor has been developed for selective detection of tyramine by combination of multiwalled carbon nanotube-gold nanoparticle (MWCNT-AuNP) composites and chitosan. MWCNT-AuNP composites were introduced for the enhancement of electronic transmission and sensitivity. Chitosan acts as a bridge for the imprinted layer and the MWCNT-AuNP composites. The molecularly imprinted polymer (MIP) was synthesized using tyramine as the template molecule, silicic acid tetracthyl ester and triethoxyphenylsilane as the functional monomers. The molecularly imprinted film displayed excellent selectivity towards tyramine. Under the optimum conditions, the current response had a linear relationship with the concentration of tyramine in the range of 1.08 × 10−7 to 1 × 10−5 mol/L, with a limit of detection 5.7 × 10−8 mol/L. The proposed sensor exhibited excellent repeatability, which was better than the result from previous literature. The relative standard deviation (RSD) of the repeated experiments for tyramine (5 mmol/L) was 7.0%. Determination of tyramine in real samples showed good recovery.

A strategy of surface-free-energy-distribution induced selective growth of Au nanograins (AuNGs) on specific positions of Cu2O octahedron surfaces with a series of morphological evolutions has been demonstrated. The surface energy distribution of Cu2O octahedra generally follows the order of {111} facets < crystal edges < vertices and leads to the preferential growth and evolution of the heterostructures. The morphological evolutions and crystal structures of Cu2O and Cu2O–Au hierarchical heterostructures are investigated and discussed. Meanwhile, Cu2O octahedra coated by different amounts of polyvinyl pyrrolidone (PVP) and HAuCl4 were taken as control and the results indicate that the trend in the selective growth on PVP coated Cu2O octahedra decreased significantly because of the reducing diversity of the surface-free-energy-distribution. The identity and crystal phase structures of these Cu2O, Cu2O–Au and Cu2O–PVP–Au heterostructures are manifested through X-ray diffraction (XRD) and energy-dispersive X-ray spectrometers (EDS). X-ray photoelectron spectroscopy (XPS) further probes the surface chemical compositions and chemical oxidation state of the as-prepared Cu2O and Cu2O–Au hierarchical heterostructures and test the galvanic reaction between Cu2O and AuCl4−. The growth mechanism of the surface-free-energy-distribution induced selective growth of AuNGs on Cu2O octahedra with morphological evolution is also discussed. The photocatalytic performances of the as-prepared Cu2O and Cu2O–Au hierarchical heterostructures for the degradation of methyl orange (MO) are investigated and the results suggest the substantially enhanced photocatalytic activity of these heterostructures.

The green natural compounds, tea polyphenols (TP), were introduced to synthesize well-dispersed Au nanoparticles (AuNPs) in polyacrylonitrile (PAN) nanofibers by combining an in situ reduction approach and electrospinning technique. The AuNPs were firstly synthesized in aqueous solution to test the reducibility of the TP. Then, the well-dispersed AuNPs in PAN nanofibers were obtained by an in situ reduction approach and electrospinning technique. Fourier transform infrared spectroscopy (FTIR) was utilized to confirm the reducibility of TP. The transmission electron microscopy (TEM) and the ultraviolet-visible spectroscopy (UV-Vis) demonstrated the formation of AuNPs and their morphology. Surprisingly, compared with the AuNPs in aqueous solution, the AuNPs in PAN nanofibers via electrospinning were much smaller and well-dispersed and it was attributed to the stabilization effect of PAN through the chelating effect between gold and cyano groups. Apart from the reducibility effect, TP also served as a stabilizer together with PAN to prevent the aggregation of AuNPs effectively, which were testified by X-ray photoelectron spectroscopy (XPS) results.

Rose-petal-shaped MoS2 hierarchical nanostructures were designed and constructed using carbonized electrospun nanofibers as a template, which exhibit highly structure-sensitive properties for the hydrogen evolution reaction (HER). We first synthesized carbon nanofiber (CNF) mats by combining the electrospinning and carbonization processes, and then the CNF mats were used as a substrate for the direct growth of MoS2 nanocrystals via the CVD method. By controlling the MoS2 morphology at the nanoscale, we constructed evolutions in the structures and preferentially exposed more catalytically active edge sites, enabling improved performance for electrochemical catalytic activity. Because of their highly exposed edges and excellent chemical and electrical coupling to the underlying CNFs, MoS2–CNF fiber mats exhibited excellent HER activity with a small overpotential of ∼0.12 V and a small Tafel slope of 45 mV per decade. Our findings provide a feasible way to design and engineer advanced nanostructures for catalysis, electronic devices, and other potential applications.

We developed a facile method to synthesize porous and N-rich carbon materials derived from Bombyx mori silk cocoons with an activation and thermal carbonization process. The silk-derived nanosheets carbon fibers consist of a porous and multilayer structure, endowing the materials with high surface area of 349.3 m2 g−1 and much exposed active sites. The synthesized N-rich (4.7%) carbon materials are employed as electrocatalysts for hydrogen evolution reaction (HER) and exhibit incredible catalytic performance as well as promising electrochemical durability, which are mainly attributed to the large amount of exposed active sites, high graphitization degree and the rich nitrogen elements, especially pyridine-N and graphitic-N. Typically, the silk-derived nanosheets carbon fibers activated by KCI afford a low onset potential of −63 mV (vs. RHE), a low overpotential of 137 mV at 10 mA cm−2 and a Tafel slope of 132 mV dec−1. The results may offer a novel and promising method for the preparation of non-metal HER catalysts derived from abundant biomass.

A facile strategy for the preparation of novel Pt nanoparticles/carbon nanofibers (PtNPs/CNFs) nanostructure by combining the electrospinning and carbonization process is demonstrated. PtNPs were obtained in polyacrylonitrile nanofibers (PANFs) through an in situ reduction as well as electrospinning, and then the PtNPs/PANFs nanostructure was converted to PtNPs/CNFs following a carbonization process. The formation and structure of the synthesized PtNPs/CNFs nanostructure were systematically characterized, suggesting that PtNPs with diameter of ca. 8.8 nm were evenly dispersed in CNFs and nearly no aggregation was observed. The results indicate that the nanostructure possesses high catalytic activity for both hydrogen evolution reaction (HER) and electrochemical sensor, as well as long-term stability for HER, serving as a bifunctional catalyst. The present investigations provide a general route for the fabrication of novel electrocatalyst, which may also be extended to synthesize other metal nanoparticles/CNFs nanostructures.

1D hollow nanostructures combine the advantages of enhanced surface‐to‐volume ratio, short transport lengths, and efficient 1D electron transport, which can provide more design ideas for the preparation of highly active oxygen evolution (OER) electrocatalysts. A unique architecture of dual‐phase octahedral CoMn 2 O 4 /carbon hollow nanofibers has been prepared via a two‐step heat‐treatment process including preoxidation treatment and Ostwald ripening process. The hollow and porous structures provide interior void spaces, large exposed surfaces, and high contact areas between the nanofibers and electrolyte and the morphology can be engineered by adjusting the heating conditions. Due to the intimate electrical and chemical coupling between the oxide nanocrystals and integrated carbon, the dual‐phase octahedral CoMn 2 O 4 /carbon hollow nanofibers exhibit excellent OER activity with overpotentials of 337 mV at current density of 10 mA cm −2 and Tafel slope of 82 mV dec −1 . This approach will lead to the new perception of design issue for the nanoarchitecture with fine morphology, structures, and excellent electrocatalytic activity.

A novel, facile and green approach for the fabrication of H2O2, glutathione (GSH) and glucose detection biosensor using water-stable PVA and PVA/PEI nanofibers decorated with AgNPs by combining an in situ reduction approach and electrospinning technique has been demonstrated. Small, uniform and well-dispersed AgNPs embedded in the PVA nanofibers and immobilized on functionalized PVA/PEI nanofibers indicate the highly sensitive detection of H2O2 with a detection limit of 5 μM and exhibit a fast response, broad linear range, low detection limit and excellent stability and reusability.

Efficient bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) must be developed to realize an inexpensive water-splitting system for large-scale applications. Herein, a novel PdNi carbon nanofiber (PdNi/CNF) catalyst was synthesized by facile electrospinning and carbonization processes. The size and homogeneity of the Pd−Ni alloy nanoparticles (NPs) could be effectively tuned by controlling the molar feed ratio of metal precursors .The morphology and structure of the PdNi/CNFs were characterized, and the working electrodes fabricated from the prepared catalyst mats were directly employed in the HER and OER. The PdNi/CNFs-1:2 catalyst exhibits high catalytic activity in the HER with a low overpotential of 55 mV at a current density of 10 mA cm−2 in an acidic solution. Moreover, under 1 M KOH electrolyte, an overpotential of 187 mV is required in the HER over the catalyst to arrive 10 mA cm−2 and an overpotential of 289 mV is achieved in the OER at the same current density. The superior HER and OER activities of the PdNi/CNFs are attributed to the synergistic effects of the PdNi alloy nanoparticles (NPs) assembled on the CNFs. This work provides a simple route for synthesizing highly efficient bifunctional electrocatalysts from 3d transition metals and a small amount of noble metals for hydrogen and oxygen evolution reactions.

The bimetallic Au–Cu alloy nanoparticles have been constructed in electrospun carbon nanofibers (Au–Cu/CNFs), employing as high efficient hydrogen evolution reaction (HER) electrode. The morphology, structure, and composition of bimetallic Au–Cu alloy can be controlled by adjusting the precursor nanofibers through a facile approach. With the increased Cu content, the Au–Cu alloy have a transition from the homogeneous AuCu3 alloy phase to the Au3Cu phase with Cu shell. The self-supported bimetallic Au–Cu/CNFs hybrid can be directly employed as electrode materials for water splitting, and it showed excellent electrochemical activity, including long-term stability, high exchange current density, and low overpotential. The outstanding HER performance could be mainly attributed to the synergistic interactions and interfacial effects of Au–Cu alloy with high densities of uncoordinated surface atoms. In addition, the fast charge transport and the fast kinetic for the desorption of the gas were originated from the self-supported three-dimensional architectures consist of integrated Au–Cu/CNFs networks. The Au–Cu/CNFs with mass ratio of 1:2 (Au3Cu–Cu “core-shell” alloy) obtain the lowest overpotential of 83 mV (at j = 10 mA cm–2), lowest Tafel slope of 70 mV dec–1, and highest exchange current density of 0.790 mA cm–2. The present investigations offer a new strategy for the design and synthesis of unique nanocrystals in energy conversion related application.

Regulating chemical bonds to balance the adsorption and disassociation of water molecules on catalyst surfaces is crucial for overall water splitting in alkaline solution. Here we report a facile strategy for designing Ni2W4C-W3C Janus structures with abundant Ni-W metallic bonds on surfaces through interfacial engineering. Inserting Ni atoms into the W3C crystals in reaction progress generates a new Ni2W4C phase, making the inert W atoms in W3C be active sites in Ni2W4C for overall water splitting. The Ni2W4C-W3C/carbon nanofibers (Ni2W4C-W3C/CNFs) require overpotentials of 63 mV to reach 10 mA cm-2 for hydrogen evolution reaction (HER) and 270 mV to reach 30 mA cm-2 for oxygen evolution reaction (OER) in alkaline electrolyte, respectively. When utilized as both cathode and anode in alkaline solution for overall water splitting, cell voltages of 1.55 and 1.87 V are needed to reach 10 and 100 mA cm-2, respectively. Density functional theory (DFT) results indicate that the strong interactions between Ni and W increase the local electronic states of W atoms. The Ni2W4C provides active sites for cleaving H-OH bonds, and the W3C facilitates the combination of Hads intermediates into H2 molecules. The in situ electrochemical-Raman results demonstrate that the strong absorption ability for hydroxyl and water molecules and further demonstrate that W atoms are the real active sites.

Developing highly efficient electrocatalysts while revealing the active site and reaction mechanism is essential for electrocatalytic water splitting. To overcome the number and location limitations of defects in the electrocatalyst induced by conventional transition-metal atom (e.g. Fe, Co, and Ni) surface doping, we report a facile strategy of substitution with lower electronegative vanadium in the cobalt carbide, leading to larger amounts of defects in the whole lattice. The self-supported and quantitatively substituted VxCo3–xC (0 ≤ x ≤ 0.80) was one-step synthesized in the electrospun carbon nanofibers (CNFs) through the solid-state reaction. Particularly, the V0.28Co2.72C/CNFs exhibit superior hydrogen evolution reaction and oxygen evolution reaction activity and deliver a current density of 10 mA cm–2 at 1.47 V as the alkaline electrolyzer, which is lower than the values for the Pt/C–Ir/C couple (1.60 V). The operando Raman spectra and density functional theory calculations show that the enhanced electron transfer from V to the orbit of the Co atom makes Co a local negative charge center and leads to a significant increase in efficiency for overall water splitting.

Advanced Pt-based ternary nanocatalysts display dramatically enhanced utilization efficiency of Pt alternative to mono- and bi-counterparts, owing to the synergistic effects of the tri-metals. Herein, multicomponent uniform 3D PtCoRh highly branched nanoassemblies (HBNAs) were prepared by glycine-assisted one-pot solvothermal method in oleylamine (OAm). The effects of the precursor types, reaction time and amount of glycine were critically investigated in this synthesis. The as-prepared PtCoRh HBNAs displayed outstanding electrocatalytic activity and improved stability towards ethanol oxidation reaction (EOR) and methanol oxidation reaction (MOR) in 1 M KOH electrolyte, whose mass/specific activities were 1.75 A mg-1/4.03 mA cm-2 and 0.98 A mg-1/2.34 mA cm-2, respectively, which were remarkably higher than commercial Pt/C (0.85 A mg-1/4.03 mA cm-2 and 0.47 A mg-1/0.89 mA cm-2). This study provides some novel guidelines to fabricate advanced multimetallic electrocatalysts for practical applications in direct alcohol fuel cells (DAFCs).

Abstract Photooxidation under sunlight has potential in organic synthesis, bacterial killing, and organic waste treatment. Photosensitizers (PSs) can play an important role in this process. High 1 O 2 generation efficiency and excellent photostability under sunlight, as well as easy recyclability are ideal properties for PSs, but are not easy to achieve simultaneously. Herein, a pure organic porous conjugated polymer PS, CPTF, shows great photostability, large specific surface area, and high 1 O 2 generation efficiency under sunlight for photooxidation. For the oxidation of aromatic aldehyde to aromatic acid, the PS catalyst shows excellent recyclability, and enables solvent‐free reactions in high yields both under direct sunlight and simulated AM 1.5G irradiation. In addition, the successful application of CPTF as an antibacterial agent and organic waste decomposition under simulated AM 1.5G irradiation indicates the potential of CPTF in sunlight‐induced waste water treatment.

Nano-porous carbon materials derived from various natural plants are fabricated by a facile, cost-effective and efficient approach. The influence of well-dispersed intrinsic elements in different precursors and chemical activation process under different temperatures on the morphology, surface chemistry, textural structures and electrochemical performance have been studied and analysed in detail. These as-prepared nano-porous carbons possess high accessible surface area (685.75–3143.9 m2 g−1), well-developed microporosity and high content of naturally-derived heteroatom functionalities (16.43 wt%). When applied as electrode materials for supercapacitors in a three-electrode system with 6 M KOH, the obtained nano-porous carbons derived from lotus leaves at 700oC possess a high specific capacitance of 343.1 F g−1 at 0.5 A g−1 and a capacitance retention of 96.2% after 10000 cycles at 5 A g−1. The assembled symmetrical supercapacitor presents a high energy density of 24.4 Wh kg−1 at a power density of 224.6 W kg−1 in Na2SO4 gel electrolyte. This work provides guiding function for unified and large-scale utilization of agricultural biomass waste. The obtained sustainable activated carbon products can be used in diverse applications.

The appropriate catalyst model with a precisely designed interface is highly desirable for revealing the real active site at the atomic level. Herein, we report a proof-of-concept strategy for creating an exposed and embedding interface model by constructing a unique Co9S8 core with a full WS2 shell (Co9S8/FWS2) and a half WS2 shell (Co9S8/HWS2) to uncover the synergistic effect of heterointerfaces on the catalytic performances. Tailoring the heteroepitaxial growth of WS2 shell, Co9S8/HWS2 with exposed Co–S–W interfaces leads to the exceptional electron density changes on edged-S atoms with large amounts of lone-pair electrons. Meanwhile, the unique Co9S8/HWS2 could accelerate the kinetic adsorption of hydrogen- and oxygen-containing intermediates. Such Co9S8/HWS2 electrocatalysts show extremely low overpotentials of 78 and 290 mV at a current density of 10 mA cm–2 for hydrogen evolution reaction (HER) and oxygen evolution reaction, respectively. Using Co9S8/HWS2 as both the cathode and anode, an alkali electrolyzer delivers a current density of 10 mA cm–2 at a quite low cell voltage of 1.60 V. The results of both operando Raman spectroscopy and electron spin resonance indicate the presence of S–S terminal and S–S bridging with unsaturated S atoms during the HER process. The present work reveals the synergistic effects of nanoscale interfaces on overall electrocatalytic water splitting.

The design of core-shell nanocomposites has become a valid solution to improve the electrochemical performance of materials. This study reports a simple and extensible method for preparing N-doped carbon-coated NiS core-shell composites at different temperatures (300 °C and 500 °C, denoted as [email protected], [email protected]). We discussed the effect of pyrolysis temperature on composites. At high temperature, the coating of PDA protects the original crystalline structure and microstructure of NiS to a certain extent, lowering the original high temperature instability of NiS. In addition, the core-shell structure contributes to adapting and buffering the volume change of NiS in charge-discharge cycles. Moreover, carbon layer tightly connects NiS nanoparticles to form a stable interconnected network framework structure to enhance electrochemical stability. Benefiting from these structural advantages, [email protected] exhibits a higher specific capacity of 665C g−1 (1330 F g−1) at 0.5 A g−1 and significantly enhanced cycle stability that 92.3% of the initial capacity is retained over 3000 cycles at 10 A g−1, which are far better than NiS. An asymmetric supercapacitor (ASC) comprised of [email protected] and the commercial activated carbon (AC) electrodes delivers a high energy density of 28.6 Wh kg−1 at the power density of 884.5 W kg−1 and shows great cycle stability with the retention of 81.7% after 3000 cycles. [email protected] demonstrates its attractive potential in the domain of practical energy storage devices.

A synergetic confinement method is proposed for high-entropy alloy nanoparticles (HEA-NPs) synthesis. Carbon nitride matrix and polydopamine coating contribute to the homogeneous NPs formation. The HEA-NPs show superior electrocatalytic property.

A type II heterojunction CdS/TpPa-1 with enhanced photocatalytic N 2 fixation performance was constructed by anchoring ultrafine CdS nanoparticles in the TpPa-1-COF matrix.

Metal and covalent organic frameworks (MOFs/COFs) are emerging promising candidates in the field of catalysts due to their porous nature, chemically well-defined active sites and structural diversity. However, they are typically provided with poor electrical conductivity, which is insufficient for them to work as satisfying electrocatalysts. Designing and fabricating MOFs/COFs with high conductivity presents a new avenue towards special electrochemical reactions. This minireview firstly highlighted the origin and design principles of conductive MOFs/COFs for electrocatalysis on the basis of typical charge transfer mechanisms, that is "through space", "extended conjugation" and "through bond". An overview of conductive MOFs/COFs used in the electrocatalytic carbon dioxide reduction reaction (CO2RR), water splitting and the oxygen reduction reaction (ORR) was then made to track the very recent progress. In the final remarks, the present challenges and perspectives for the use of conductive MOFs/COFs as electrocatalysts including their structural optimization, feasible applications and structure-activity correlation are proposed.

The methanol-poisoning of electrocatalysts at the cathodic part of direct methanol fuel cells (DMFCs) can severely degrade the overall efficiency. Therefore, engineering cathodic catalysts with outstanding oxygen reduction activity, and simultaneously, superior methanol tolerance is greatly desired. Herein, bimetallic palladium-copper (PdCu) nanoplates with the optimized d-band center are designed as promising cathodic catalysts for DMFCs. It shows outstanding oxygen reduction activity with a mass activity (MA) of 0.522 A mgPd-1 in alkaline electrolyte, overwhelming the benchmarked commercial Pt/C and Pd/C. Meanwhile, it has prominent stability with only 4.0 % loss in MA after continuous 20 K cycles. More importantly, the PdCu nanoplates are almost inert toward methanol oxidation and show excellent anti-methanol capability. The theoretical calculations reveal that the downshift of d-band center in PdCu nanoplates and the electronic interaction between Pd and Cu atoms could effectively lower the methanol adsorption energy, thus leading to enhanced methanol tolerance. This work highlights the important role of tuning the electronic structure and optimized geometry of electrocatalysts to simultaneously boost their oxygen reduction activity, stability, and methanol tolerance for their future application in DMFCs.

A steric hindrance strategy was used to prepare intramolecular hydrogen bond-controlled thermosensitive fluorescent carbon dots (CDs) via the solvothermal treatment of o-phenylenediamine respectively with three dihydroxybenzene isomers. The CDs obtained from different isomers have very similar morphology, surfaces, and photophysical properties but exhibited different thermal sensitivities. Meanwhile, the orange-emitting CDs (p-CDs) obtained from o-phenylenediamine and p-hydroquinone exhibited an optimal thermal sensitivity of 1.1%/°C. Comprehensive experimental characterizations and theoretical calculations revealed that even a small difference in substituent locations in the phenyl ring of the precursors can considerably affect the formation of intramolecular hydrogen bonds and that the CDs with strong intramolecular hydrogen bonds exhibited poor thermosensitivity. The p-CDs were incorporated with reference CDs (B-CDs) that exhibited heating-quenching blue emission through electrostatic self-assembly to construct a dual-emission probe (p-CDs/B-CDs), which exhibited a thermal sensitivity of 2.0%/°C. Test strips based on the p-CDs/B-CDs were prepared to measure temperature fluctuations based on sensitive and instant fluorescence color evolution. Further, this fluorescent colorimetry was successfully applied to a test strip-integrated wearable wristband to measure the body temperature. This study establishes an inherent relationship between precursors and the resulting intramolecular hydrogen bonds for precisely tuning the thermal sensitivity of CDs. It also offers a visual quantitative strategy for the early warning of abnormal body temperatures.

We developed a series of single atom catalysts (SACs) anchored on bipyridine-rich COFs. By tuning the active metal center, the optimal Py-Bpy-COF-Zn shows the highest selectivity of 99.1% and excellent stability toward H2O2 production via oxygen reduction, which can be attributed to the high *OOH dissociation barrier indicated by the theoretical calculations. As a proof of concept, it acts as a cathodic catalyst in a homemade Zn-air battery, together with efficient wastewater treatment.

The content of triacylglycerols (TAG) in krill oil is generally omitted from the labels of commercial supplements and unacknowledged in studies aimed at proving its health benefits. The present study demonstrates that TAG compounds, in addition to phospholipids and lysophospholipids, are an important lipid class in pure krill oil. The fatty acid composition of TAG molecules from krill oil and their distribution on the backbone of TAG structures were determined by gas chromatography and liquid chromatography tandem mass spectrometric, respectively. The content of omega 3 polyunsaturated fatty acids (n-3 PUFA) was similar to those reported in the literature for fish oil. It was estimated that 21 % of n-3 PUFA were at the sn-2 position of TAG structures. To our knowledge, this is the first determination and structural characterization of TAG in pure krill oil supplements.

Using tea polyphenols (TPs) as a reductant, Ag nanoparticles (AgNPs) supported on halloysite nanotubes (HNTs) were simply and greenly synthesized for the photocatalytic decomposition of methylene blue (MB). HNTs were initially functionalized by N-β-aminoethyl-γ-aminopropyl trimethoxysilane (AEAPTMS) to introduce amino groups to form N-HNTs to fasten the AgNPs; then AgNPs were synthesized and ‘anchored’ on the surface of the HNTs. Fourier transform infrared spectroscopy was employed to testify the amino groups on the surface of the HNTs. Transmission electron microscopy, field-emission scanning electron microscopy and x-ray diffraction were utilized to characterize the structure and morphology of the synthesized HNTs supported by the AgNPs (AgNPs@N-HNTs). The results showed that the AgNPs had been synthesized and ‘anchored’ onto the surface of the HNTs with a diameter of about 20–30 nm. X-ray photoelectron spectroscopy analysis revealed the chelating interaction between the AgNPs and N atoms together with the TP molecular. The photocatalytic activity of the as-prepared AgNPs@N-HNTs catalyst was evaluated by decomposition of MB; the results showed that the prepared catalyst exhibited excellent catalytic activity and high adsorption capability to MB.

Using epigallocatechin gallate (EGCG) as both a green reductant and stabilizer, ultrafine noble metal nanoparticles (Rh NPs, Pt NPs, Pd NPs) are synthesized and in situ deposited within amino-functionalized halloysite nanotubes (N-HNTs) via a facile and eco-friendly process. These noble metal nanoparticles with extremely small size (∼1.5 nm) are dispersed densely and uniformly on both outside and inside surface of N-HNTs. Rh deposited N-HNTs (Rh–N-HNTs) was investigated as a model composite catalyst and applied in the catalytic reduction of 4-nitrophenol (4-NP), and it exhibited amazing activity and recycle stability. Due to the green and flexibility of the technique described here, noble metal nanoparticles, metal nanoalloy, or metal oxide nanoparticles with ultrafine particle size also can be loaded densely and uniformly on the surface of diverse amino-functionalized nanotubes, nanofibers or nanoporous, and these composites may be applicable in catalysis, photocatalysis, and electrochemical areas.

In this study, a facile and effective approach was demonstrated for designing and preparing small Cu nanoparticles (NPs) densely and uniformly distributed on carbon nanofibers (CNFs). Self-supported hybrid CuNPs/CNFs with three-dimensional (3D) architectures were prepared via electrospinning and thermal reduction processes. The hybrid CuNPs/CNFs were directly used as electrodes for an electrocatalytic hydrogen evolution reaction (HER), and they exhibited excellent activity, with a low onset potential of only 61 mV, an overpotential of 200 mV at 10 mA cm−2, a small Tafel slope (152 mV dec−1) and a long-term stability in acidic electrolyte. The 3D self-supported architecture exhibited a high conductivity, a large specific surface area and a high porosity, all of which are beneficial for the access of electrolyte for the CuNPs and the release of the formed H2, thereby reducing the overpotentials and accelerating the electrode kinetics. This work demonstrates that CuNPs/CNFs are promising candidates for the substitution of noble metal Pt-based materials in producing the HER from water.

We have demonstrated a facile approach for the fabrication of flexible and reliable sulfydryl functionalized PVA/PEI nanofibers with excellent water stability for the self-assembly of Au nanocrystals, such as Au nanoparticles (AuNPs), Au nanoflowers (AuNFs) and Au nanorods (AuNRs), used as the highly efficient surface-enhanced Raman scattering (SERS) substrates for the detection of rhodamine B (RhB). Various methods were employed to cross-link the PVA nanofibers with better morphology and porous structures after immersing in water for desired times. Various SERS-active Au nanocrystals, such as AuNPs, AuNFs, and AuNRs have been successfully synthesized. After the grafting of MPTES on the cross-linked PVA/PEI nanofibers, the Au nanocrystals can easily be self-assembled on the surfaces of the nanofibers because of the strong interactions of the Au–S chemical bondings. The Au nanocrystals self-assembled throughout the PVA/PEI nanofibers used as SERS substrates all exhibit enhanced SERS signals of RhB compared with their individual nanocrystals. It is mainly due to the close interparticle distance, mutual orientation and high density of “hot” spots, that can strongly affect the overall optical response and the SERS enhancement. By changing the amounts of the self-assembled AuNFs on the nanofibers, we can control the density of the “hot” spots. With the increased amounts of the AuNFs throughout the nanofibers, the SERS substrates show enhanced Raman signals of the RhB, indicating that the increased density of “hot” spots can directly lead to the SERS enhancement. The AuNFs/(PVA/PEI) SERS substrates show good sensitivity, reliability and low detection limit (10−9 M). The presented approach can be broadly applicable to the assembly of different types of plasmonic nanostructures and these novel materials with strong SERS enhancement can be applied in bioanalysis and biosensors.

Abstract Multifunctional flexible sensors that are sensitive to different physical and chemical stimuli but remain unaffected by any mechanical deformation and/or changes still present a challenge in the implementation of flexible devices in real‐world conditions. This challenge is greatly intensified by the need for an eco‐friendly fabrication technique suitable for mass production. A new eco‐friendly and scalable fabrication approach is reported for obtaining thin and transparent multifunctional sensors with regulated electrical conductivity and tunable band‐gap. A thin (≈190 nm thickness) freestanding sensing film with up to 4 inch diameter is demonstrated. Integration of the freestanding films with different substrates, such as polyethylene terephthalate substrates, silk textile, commercial polyethylene thin film, and human skin, is also described. These multifunctional sensors can detect and distinguish between different stimuli, including pressure, temperature, and volatile organic compounds. All the sensing properties explored are stable under different bending/strain states.

Finding cost-effective, active and durable catalyst materials for energy applications, such as electrocatalytic hydrogen production, is an intriguing challenge. Here, a facile and effective approach to the design and construction of two-dimensional MoS2 and WS2 interleaved nanowalls with maximum exposures of active edges on silk-derived N-doped carbon fibers (SNCF) was demonstrated. The morphological evolutions of the MoS2 and WS2 nanocrystals on the SNCF from crescent-like nanosheets to an interleaved nanowall network can be obtained by adjusting the concentrations of the Mo and W precursors. These robust MoS2/SNCF and WS2/SNCF electrocatalysts exhibit prominent hydrogen evolution reaction (HER) activities with onset potentials of −40 and −96 mV and Tafel slopes of 60 and 66 mV dec−1, respectively. The overpotentials (η) at j = −10 mA cm−2 for MoS2/SNCF and WS2/SNCF are −102 and −157 mV, respectively. In addition, MoS2/SNCF and WS2/SNCF are both able to sustain continuous HER operation for 10 h under working conditions with only a slight degradation in current densities, implying excellent durability and a prospect for practical applications.

Abstract A novel and sensitive fluorescence analysis platform was constructed for the detection of chlorogenic acid (CGA) using carbon dots (C‐dots) with prominent sensitivity and selectivity. Excitation‐dependent emission fluorescence C‐dots were fabricated using citric acid and l ‐histidine as precursors through an efficient one‐step hydrothermal treatment. The maximum excitation and emission wavelength of the as‐synthesized C‐dots were 340 nm and 414 nm, respectively. Moreover, the as‐prepared C‐dots displayed excellent water solubility and good photostability. The fluorescence quantum yield of the as‐prepared C‐dots was measured to be about 22% using quinine sulfate as the reference. Furthermore, the obtained C‐dots were applied to the detection of CGA accompanied with a wide linear range from 1.53 μmol L −1 to 80.0 μmol L −1 as well as a limit detection of 0.46 μmol L −1 . More importantly, the proposed fluorescence method was successfully used to analyse CGA in coffee and honeysuckle.

We summarized here the recent progress and perspectives on single-atom catalysts for electrochemical clean energy conversion.

Development of highly effective and stable electrocatalysts is urgent for various energy conversion applications. Herein, a facile co-reduction approach was developed to fabricate three-dimensional (3D) hyperbranched PtRh nanoassemblies (NAs) under solvothermal conditions, where creatinine and cetyltrimethylammonium chloride (CTAC) were employed as the structure-directing agents. The as-synthesized nanocatalyst exhibited intriguing catalytic characters for hydrogen evolution reduction (HER) with a low overpotential (20 mV) at 10 mA cm−2 and a small Tafel slope (49.01 mV dec−1). Meanwhile, the catalyst showed remarkably enlarged mass activity (MA: 2.16/2.02 A mg−1) and specific activity (SA: 4.16/3.88 mA cm−2) towards ethylene glycol and glycerol oxidation reactions (EGOR and GOR) alternative to commercial Pt black and homemade Pt3Rh nanodendrites (NDs), PtRh3 NDs and Pt nanoparticles (NPs). This method offers a feasible platform to fabricate bifunctional, efficient, durable and cost-effective nanocatalysts with finely engineered structures and morphologies for renewable energy devices.

A novel strategy is developed for controlled synthesis of hyper-dendritic PdZn nanocrystals as efficient bifunctional electrocatalysts toward ORR and EOR. • A novel strategy is developed for synthesis of hyper-dendritic PdZn nanocrystals. • The HD-PdZn NCs have ample pores, hyper-dendritic morphology and electron effect. • The HD-PdZn NCs exhibit enhanced ORR and EOR activity and durability. • DFT calculation proved that the reduction of OOH* to OH* is accelerated during ORR. Although attentions have been devoted to developing Pd-based bimetallic nanocrystals towards the electrocatalytic oxygen reduction reaction (ORR) and ethanol oxidation reaction (EOR), the engineering of efficient bifunctional electrocatalysts with high atomic utilization still faces big challenges. Herein, we reported a facile one-pot template-free route to fabricate three-dimension hyper-dendritic PdZn nanocrystals (HD-PdZn NCs) that regulated by gas mixtures of carbon monoxide and hydrogen. The developed catalysts acted as robust bifunctional electrocatalysts for cathodic ORR and anodic EOR. Specifically, the engineered HD-PdZn NCs not only displayed superior mass activity (MA, 0.461 A mg Pd -1 ) and specific activity (SA, 0.393 mA cm −2 ) at 0.9 V, which were 5.2 and 5.0 times of commercial Pt/C, respectively, but also showed enhanced stability with only 3% loss of MA after 10,000 cycles for ORR. Density functional theory (DFT) calculations revealed the Zn implantation could facilitate the reduction of OOH* to OH* on the surface of Pd during the ORR process. Moreover, HD-PdZn NCs exhibited the highest EOR mass activity with a value of 3.45 A mg Pd −1 among benchmarked catalysts in alkaline solution. The advantageous structural features and electron effects are proposed to be responsible for the remarkable bifunctional activities. This work illustrates a facile method to fabricate highly efficient bifunctional electrocatalyst for energy conversation application.

The construction of heterojunctions is considered an effective way to improve the photocatalytic performance of bismuth-based photocatalysts. In this research, Bi2O3/BiFeO3 heterojunction nanofibers with rich oxygen vacancies were successfully synthesized via the in-situ growth of Bi2O3 nanosheets on the surface of BiFeO3 nanofibers, and were then reduced in N, N-dimethylformamide (DMF) via the solvothermal method for different times. The composite ratios and oxygen vacancy concentrations were then systematically optimized. The optimal composite with the molar ratio of BiFeO3:Bi2O3 = 1:1 and solvothermally reducted in DMF for 3 h was found to completely degrade the tetracycline hydrochloride (TC) solution within 120 min, and its photodegradation rate was 8.7 and 5.4 times higher than those of pure BiFeO3 and Bi2O3, respectively. The enhancement can be ascribed to the synergistic effect of the p-n heterojunction formed at the interface and oxygen vacancies produced on the surface, which significantly increased the absorption of visible light, inhibited the recombination of photogenerated electron-hole pairs, and accelerated the separation and transfer of photogenerated charges. Moreover, the obtained oxygen vacancy-enriched Bi2O3/BiFeO3 heterojunction nanofibers exhibited good cyclic stability and magnetic separation capability, and therefore have potential applications in practical sewage treatment.

Solar-driven interfacial evaporation has been considered a promising approach to solve clean water scarcity with minimum environmental impact. Herein, we rationally developed a flexible, floating, and high-efficiency solar-driven interfacial water evaporation device by designing a hierarchical structure (NiCoxSy-PANI@GF) in which numerous NiCoxSy nanosheets were vertically and densely grown on a polyaniline (PANI)-modified glass fiber (GF) membrane. The NiCoxSy-PANI@GF with honeycomb-like structures and rough surfaces could produce multiscattering of incident solar light and convert it into heat at the air–water interface. Simultaneously, the hydrophilic NiCoxSy-PANI@GF modified by PANI coating could provide continuous and rapid water supply via the capillary wicking effect. The GF substrate with low thermal conductivity thermally localizes solar heating at the air–water interface by suppressing underline heat loss. The NiCoxSy-PANI@GF achieves a broad-spectrum light absorption rate of 96%, an evaporation rate of 1.30 kg m–2 h–1, and a solar-to-steam efficiency of 78.7% under one solar irradiation. In practical desalination, the homemade devices afford continuous stable operation over 20 h and 15 evaporation cycles. Meanwhile, the excellent hydrophilicity ensures the high salt-resistance ability and excellent self-cleaning performance. Additionally, the high stability and scalability in harsh conditions make the NiCoxSy-PANI@GF competitive for practical full-spectrum and large-scale solar energy harvesting.

Binary transition metal chalcogenide core–shell nanocrystals are considered the most promising nonprecious metal catalysts for large-scale industrial hydrogen production. Herein, we report a one-dimensional, space-confined, solid-phase strategy for the growth of a Cu9S5@MoS2 core–shell heterostructure by combining electrospinning and chemical vapor deposition methods. The Cu9S5@MoS2 core–shell nanocrystals were synthesized in situ on carbon nanofibers (Cu9S5@MoS2/CNFs) by an S vapor graphitization process. Tuning of the MoS2 shell numbers can be controlled by changing the mass ratio of the Cu and Mo precursors. We experimentally determined the effects of the thickness of the MoS2 shell on the electrocatalytic activity for the hydrogen evolution reaction (HER) in acidic and alkaline solutions. When the mass ratio is 3:1, the Cu9S5@MoS2/CNFs show the fewest MoS2 shells with just 1–2 layers each and exhibit the best HER performance with small overpotentials of 116 mV and 114 mV in acidic and alkaline solutions, respectively, at a current density of 10 mA cm−2. The core shell structures, with their unique Cu-S-Mo nanointerfaces, could enhance the electron transfer and surface area, thus increasing the performance of the HER. This work provides a facile method to design unique core shell assemblies in one-dimensional nanostructures.

Rational development of low-cost, durable and high-performance bifunctional oxygen catalysts is highly crucial for metal-air batteries. Herein, transition metal alloyed FeCo nanoparticles (NPs) embedded into N-doped honeycombed carbon ([email protected]) was efficiently prepared by a one-step carbonization method in the existence of NH4Cl and citric acid. Benefiting from the honeycomb-like architectures and the synergistic effects of the FeCo alloy with the doped-carbon matrix, the as-synthesized [email protected] exhibited outstanding oxygen reduction reaction (ORR) with the more positive onset potential (Eonset = 0.98 V vs. RHE) and half-wave potential (E1/2 = 0.85 V vs. RHE), coupled with outstanding oxygen evolution reaction (OER) with the lower overpotential (318 mV) at 10 mA cm−2. Besides, the home-made Zn-air battery has the larger power density of 144 mW cm−2 than Pt/C + RuO2 (80 mW cm−2). This research offers some valuable guidelines for constructing robust oxygen catalysts in clean energy storage and conversion technologies.

We report a thermally driven metal diffusion strategy for the controlled synthesis of high-entropy alloy nanocrystals using electrospun nanofibers as nanoreactors.

The recyclable, self-healing and easily-degradable transient electronic technology has aroused tremendous attention in flexible electronic products. However, integrating the above advantages into one single flexible electronic device is still a huge challenge. Herein, we demonstrate a flexible and recyclable bio-based memory device using fish colloid as the resistive switching layer on a polyimine substrate, which affords reliable mechanical and electrical properties under repetitive conformal deformation operation. This flexible bio-based memory device presents potential analog behaviors including memory characteristics and excitatory current response, which undergoes incremental potentiation in conductance under successive electrical pulses. Moreover, this device is expected to greatly alleviate the environmental problems caused by electronic waste. It can be decomposed rapidly in water and well recycled, which is a promising candidate for transient memories and information security. We believe that this study can provide new possibilities to the field of high-performance transient electronics and flexible resistive memory devices.

Development of advanced electrocatalytic materials is the crucial technology in electrolytic water to produce clean hydrogen energy. Herein, we have developed a highly efficient and stable hydrogen evolution reaction (HER) electrocatalyst MoS2/Ti3C2@CNFs hybrid material, which obtained by sulfur vapor assisted graphitization of Mo/Ti3C2@PAN precursor. Conductive Ti3C2 MXene and carbon nanofiber (CNFs) were applied to construct the "plane-line" skeleton structure to effectively prevent the stacking of Ti3C2 flakes, increase the loading content of MoS2, enlarge the exposure active edge sites of MoS2 and accelerate charger transfer of MoS2. MoS2/Ti3C2@CNFs exhibits excellent electrocatalytic activity and high stability in HER compared to pure MoS2 and MoS2/Ti3C2 nanostructure. The excellent performance of MoS2/Ti3C2@CNFs in HER is attributed to the special characteristics of the skeleton structure and the strong interface coupling between MoS2 and Ti3C2 MXene. Our findings provide a viable approach for designing advanced nanostructures for catalysis, electronic devices, and other potential applications.

Herein, we designed a C2+-producing catalyst by incorporating Lewis acid boron dopant into porous copper oxides nanotubes (B-CuO NTs) via a convenient electrospinning−calcination method. The B-CuO NTs catalyst achieved a 60.5% C2+ Faraday efficiency (FE) including 47% of ethanol, a 4-fold increase over CuO in a flow cell at − 0.6 V vs reversible hydrogen electrode (RHE). In situ characterizations demonstrate that the strong ability for *CO adsorption on B-CuO NTs facilitates the hydrogenation to the *CHO intermediate and promotes the C-C coupling further to *OCCHO intermediate via the proton-coupled electron transfer reactions. Theoretically calculations demonstrate that B doping induced polarized charge redistribution could suppress the *CHO transfer to C1 products by reducing the energy barrier for further OC-CHO coupling. This work provides a comprehensive understanding of Lewis acid B doping effect on regulating the C-C coupling pathway and improving the C2 selectivity.

The heterogeneity, species diversity, and poor mechanical stability of solid electrolyte interphases (SEIs) in conventional carbonate electrolytes result in the irreversible exhaustion of lithium (Li) and electrolytes during cycling, hindering the practical applications of Li metal batteries (LMBs). Herein, this work proposes a solvent-phobic dynamic liquid electrolyte interphase (DLEI) on a Li metal (Li-PFbTHF (perfluoro-butyltetrahydrofuran)) surface that selectively transports salt and induces salt-derived SEI formation. The solvent-phobic DLEI with C-F-rich groups dramatically reduces the side reactions between Li, carbonate solvents, and humid air, forming a LiF/Li3 PO4 -rich SEI. In situ electrochemical impedance spectroscopy and Ab-initio molecular dynamics demonstrate that DLEI effectively stabilizes the interface between Li metal and the carbonate electrolyte. Specifically, the LiFePO4 ||Li-PFbTHF cells deliver 80.4% capacity retention after 1000 cycles at 1.0 C, excellent rate capacity (108.2 mAh g-1 at 5.0 C), and 90.2% capacity retention after 550 cycles at 1.0 C in full-cells (negative/positive (N/P) ratio of 8) with high LiFePO4 loadings (15.6 mg cm-2 ) in carbonate electrolyte. In addition, the 0.55 Ah pouch cell of 252.0 Wh kg-1 delivers stable cycling. Hence, this study provides an effective strategy for controlling salt-derived SEI to improve the cycling performances of carbonate-based LMBs.

Well‐dispersed PtCu alloy nanoparticles (NPs) with a diameter of only ≈2 nm encapsulated in carbon nanofibers (CNFs) are synthesized using electrospinning technology followed by a graphitization process in a chemical vapor deposition furnace. Distinctly, even with a small amount of Pt, the PtCu/CNFs‐1:2 catalyst possesses outstanding hydrogen evolution reaction (HER) activity, including small overpotential, long‐term stability, and a high exchange current density as well as large double layer capacitance ( C dl ). The excellent HER performance of the PtCu/CNFs‐1:2 catalyst is attributed to the synergistic interaction between Pt and Cu, the uniform distribution of the alloy NPs and the use of CNFs with 3D architectures. This development may provide a simple, efficient, and green synthesis method to design bi‐ or multimetal alloys for use as the cathode electrocatalysts for the HER or other electrocatalytic devices.

Developing stable and efficient bifunctional catalysts for overall water splitting is a critical step in the production of renewable energy sources. Here we report a stable and highly active electrocatalyst comprised of NiCoSe2-x/N-doped carbon mushroom-like core/shell nanorods on silk-derived carbon fiber through one step selenization. The unique one-dimensional nanorod structure facilitates the charge transport, and the N-doped carbon shell also increases the electrical conductivity, resulting in a remarkable enhancement of the catalytic activity. The N-doped carbon shell also functions as a protection layer. The composite catalyst therefore exhibits outstanding OER and HER performance, it can also stably drive the overall water splitting at a low cell voltage of 1.53 V in base solution. The present work provides an efficient strategy for the fabrication of stable and active electrocatalysts with earth-abundant elements.

Binary transition metal dichalcogenides (TMDs) usually exhibit high hydrogen evolution reaction (HER) activities; however, the facile and efficient synthesis of ternary TMDs alloys remains a challenge. In this study, we reported an efficient method of synthesis for a MoS2(1−x)Se2x ternary alloy in a CVD system, and carbon nanofibers serve as the substrate. The MoS2(1−x)Se2x/CNFs hybrids were directly used as hydrogen evolution cathodes and exhibit lower onset potentials and excellent durability, suggesting they have significantly enhanced catalytic activity and could serve as effective and promising catalysts for the HER.

In this study, excitation-independent emission nitrogen and sulfur co-doped fluorescence carbon dots (N,S-CDs) was fabricated by using a simple and efficient one-step hydrothermal treatment with sodium citrate and thiourea as precursor. We found that the obtained N,S-CDs displayed excellent optical properties and emitted strong blue fluorescence under the 365 nm UV lamp. The relative quantum yield was as high as 26.9% using quinine sulfate as reference. The fluorescence of N,S-CDs could be effectively quenched when curcumin(CM) was added into the solution based on the inner filter effect (IFE). The as-prepared N,S-CDs without any modification could be as switch-off fluorescent probe for fluorescence turn-off detection of CM in the range of 0.15–18.0 μmol L−1 with the detection limit of about 0.04 μmol L−1. Moreover, the as-prepared N,S-CDs were successfully employed to the detection of CM in urine samples with satisfactory results. Noticeably, the N,S-CDs showed a distinct temperature-sensitive feature and used to construct fluorescent temperature sensor. Therefore, a convenient approach was proposed that N,S-CDs could be used as a fluorescent probe for rapid and sensitive detection of curcumin and temperature.

Exploring and designing efficient non-noble catalysts formed by element doping and nanostructure modification for the hydrogen evolution reaction (HER) is of critical importance with respect to sustainable resources. Herein, we have prepared a three-dimensional binary NiCo phosphide with hierarchical architecture (HA) composed of NiCoP nanosheets and nanowires grown on carbon cloth (CC) via a facile hydrothermal method followed by oxidation and phosphorization. Due to its unique hierarchical nanostructure, the NiCoP HA/CC electrocatalyst exhibits excellent performance and good working stability for the HER in both acidic and alkaline conditions. The obtained NiCoP HA/CC shows excellent HER activity with a low potential of 74 and 89 mV at 10 mA cm−2, a small Tafel slope of 77.2 and 99.8 mV dec−1 and long-term stability up to 24 h in acidic and alkaline electrolyte, respectively. NiCoP HA/CC, a non-noble metal material, is a promising electrocatalyst to replace noble metal-based electrocatalysts for the HER.

Construction of heterojunction is an important means to improve photocatalytic performance. In this work, 2D/2D ZnCoMOF/g‐C 3 N 4 heterojunction photocatalyst was designed and successfully obtained by electrostatic assembly. Combing the complementary advantages of two‐dimensional MOFs and g‐C 3 N 4 , the obtained composite samples showed superior photocatalytic hydrogen evolution performance. By optimizing the composite ratios and metal centers of MOFs, g‐C 3 N 4 composited with 5 wt% bimetallic ZnCoMOF (CNZnCo5) was obtained and exhibited the highest hydrogen production rate of 1,040.1 μmol/g/h, which was 33.2 times of bulk g‐C 3 N 4 and 3.5 times of 2D g‐C 3 N 4 . Besides, the reasons for the improvement of photocatalytic hydrogen production were analyzed by a series of optical and photoelectrochemical measurements. The formation of ZnCoMOF/g‐C 3 N 4 p–n heterojunction enhanced the absorption of visible light, and the 2D/2D heterojunction shortened the distance of charges migration to the surface, thus accelerating the charges separation and transfer. This work may provide some insights into design and preparation of specific 2D/2D heterojunction with enhanced photocatalytic performance.

Covalent organic frameworks (COFs) with internal fixation of molecular active sites provide unprecedent high atom utilization and selectivity in various electrocatalysis. So far, it is still big challenge to exploit their fine tuning to enhance the catalytic performance and have insight into their advantages. In this paper, we report an ideal platform construed by COFs and multiwall carbon nanotubes (MWCNTs) to illustrate key factors in COF-based electrocatalysts towards oxygen evolution. Fine tuning of COF layers reveals the optimized catalytic performance relies on the proper loadings of molecular catalyst on MWCNTs to balance the mass and electron transfer. Moreover, a novel strategy of diluting the active sites to enhance their intrinsic activity is proposed to further enhance the electrocatalytic performance. The generality of the fine regulation is fully demonstrated with different COFs. This work elucidates the fine tuning of COF-based electrocatalysts and sheds light on the broad applications of molecular catalysts.

Dual-phase La 0.9 Sr 0.1 NiO 3 tubular perovskite oxides exhibit excellent electrochemical performance for H 2 O 2 detection with a wide linear response range of 1–7000 μM, fast response time ( t = 0.9 s), good selectivity, and admirable long-term stability.

We report a fascinating solid-phase synthesis of ultra-small CuMo solid solution alloy nanoclusters (2.1 nm) anchored on electrospun carbon nanofibers (CuMo/CNFs). By tuning the weight ratio of Cu and Mo, the optimized Cu2Mo1/CNFs achieves excellent CO2RR performance with a high faradaic efficiency (FE) of 84.5% for C2+ products and an FEethanol of 75.7%. In situ characterization demonstrates that the Cu2Mo1 alloy can strengthen the adsorption of the crucial intermediate and promote C-C coupling, leading to high selectivity and efficiency for C2+ products.

A facile and green approach has been demonstrated for the fabrication of highly uniform and monodisperse noble metal (Ag, Au, Pt) nanoparticles (NMNPs) in polyvinyl alcohol (PVA) nanofibers by combining an in situ reduction and electrospinning technique, which are used as efficient biosensor for the detection of H2O2. The small and stable NMNPs can be easily obtained in aqueous solution using EGCG as both reductant and stabilizer. Through electrospinning technique, uniform and smooth nanofibers can be obtained and the NMNPs with narrow size distributions are well dispersed in PVA nanofibers. The investigation indicates that the viscosity of the PVA solution play an important role in controlling the size of NMNPs. The fabricated AgNPs/PVA nanofibers functionalized electrodes exhibits remarkable increased electrochemical catalysis toward H2O2 and excellent stability and reusability. The biosensor allows the highly sensitive detection of H2O2 with a broad linear range span of the concentration of H2O2 from 10 μM to 560 μM. The rapid electrode response to the change of the H2O2 concentration is attributed to the fast diffusion of the H2O2 onto the surface of small AgNPs through the porous nanofibers structures.

A simple and effective method for the preparation of platinum nanoparticles (Pt NPs) grown on amino-functionalized halloysite nanotubes (HNTs) was developed. The nanostructures were synthesized through the functionalization of the HNTs, followed by an in situ approach to generate Pt NPs with diameter of approximately 1.5 nm within the entire HNTs. The synthesis process, composition and morphology of the nanostructures were characterized. The results suggest PtNPs/NH 2 -HNTs nanostructures with ultrafine PtNPs were successfully synthesized by green chemically-reducing H 2 PtCl 6 without the use of surfactant. The nanostructures exhibit promising catalytic properties for reducing potassium hexacyanoferrate(III) to potassium hexacyanoferrate(II). The presented experiment for novel PtNPs/NH 2 -HNTs nanostructures is quite simple and environmentally benign, permitting it as a potential application in the future field of catalysts.

Polyaniline (PANI) nanotubes/Au hybrid nanostructures with well-dispersed and tunable densities of Au nanoparticles (AuNPs) were fabricated through a novel, simple and green approach using electrospun polyacrylonitrile (PAN) nanofibers as sacrificial temples. Potential applications of the as-prepared PANI nanotubes/Au hybrid nanostructures as biosensor substrate materials were demonstrated through experimental studies. Transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectrometer (XPS) were employed to study the morphology and crystal structure of the novel nanostructures. Hollow nanotubular structures were shown to readily facilitate ion diffusion and improve the electronic response performance of the PANI nanotubes/Au hybrid nanostructures. The HRP–PANI nanotubes/Au hybrid nanostructures embedded with horseradish peroxidase (HRP) by immobilization methods were used as biosensor substrate materials for H2O2 detection. The HRP–PANI nanotubes/Au hybrid nanostructure biosensors were highly sensitive with a detection limit of 0.25 μM and signal-to-noise ratio (S/N) of 3.

Here we proposed a facile strategy to synthesize multi-layered gold nanoparticles/polyaniline/halloysite nanotubes (AuNPs/PANI/HNTs) nanostructures used for electrochemical sensors. The PANI/HNTs were firstly obtained by making use of the in situ polymerization as well as employing the thioglycollic acid (TA) as the dopant, thereafter, Au ions were anchored to TA and then reduced by PANI. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) observations implied that a large amount of uniform AuNPs were immobilized on the PANI/HNTs. The as-prepared AuNPs/PANI/HNTs nanostructures were also characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and the results confirmed the successful synthesis of AuNPs/PANI/HNTs nanostructures and explained the reactions in depth as well. Further investigations suggested that the AuNPs/PANI/HNTs nanostructures with well-separated AuNPs exhibited high electrochemical performance as sensors to detect hydrogen peroxide (H2O2).

In this study, novel titanium dioxide (TiO2) and zinc oxide (ZnO) hybrid photocatalysts in the form of nanofibres were fabricated by a facile method using electrospinning followed by a calcination process. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were employed to investigate the morphology and structure of the heterogeneous nanofibres. The photocatalytic performances were evaluated via the photodegradation of Rhodamine B (RhB) under irradiation with UV light. Due to the low recombination rate of photo-induced charge carriers, the high utilization efficiency of UV light and the large contact area with the target molecules, the ZnO/TiO2 hybrid nanofibres exhibited high catalytic activity towards the Rhodamine B, and the amount of Zn(OAc)2 in the precursor of these nanofibres played an important role in determining the photo decomposition performance.