Qingyu Yan

Graphene, a two-dimensional, single-layer sheet of sp(2) hybridized carbon atoms, has attracted tremendous attention and research interest, owing to its exceptional physical properties, such as high electronic conductivity, good thermal stability, and excellent mechanical strength. Other forms of graphene-related materials, including graphene oxide, reduced graphene oxide, and exfoliated graphite, have been reliably produced in large scale. The promising properties together with the ease of processibility and functionalization make graphene-based materials ideal candidates for incorporation into a variety of functional materials. Importantly, graphene and its derivatives have been explored in a wide range of applications, such as electronic and photonic devices, clean energy, and sensors. In this review, after a general introduction to graphene and its derivatives, the synthesis, characterization, properties, and applications of graphene-based materials are discussed.

Chemical vapor deposition is used to prepare novel 3D graphene networks, with ethanol as the carbon source. These networks are used as templates for the construction of graphene/metal oxide composite-based supercapacitor electrodes. As a proof of concept, NiO is deposited on 3D graphene networks. The product exhibits a high specific capacitance of about 816 F g−1 at a scan rate of 5 mV s−1 and good cycling performance.

Advanced electrodes with a high energy density at high power are urgently needed for high-performance energy storage devices, including lithium-ion batteries (LIBs) and supercapacitors (SCs), to fulfil the requirements of future electrochemical power sources for applications such as in hybrid electric/plug-in-hybrid (HEV/PHEV) vehicles.

Abstract Hybrid metal‐ion capacitors (MICs) (M stands for Li or Na) are designed to deliver high energy density, rapid energy delivery, and long lifespan. The devices are composed of a battery anode and a supercapacitor cathode, and thus become a tradeoff between batteries and supercapacitors. In the past two decades, tremendous efforts have been put into the search for suitable electrode materials to overcome the kinetic imbalance between the battery‐type anode and the capacitor‐type cathode. Recently, some transition‐metal compounds have been found to show pseudocapacitive characteristics in a nonaqueous electrolyte, which makes them interesting high‐rate candidates for hybrid MIC anodes. Here, the material design strategies in Li‐ion and Na‐ion capacitors are summarized, with a focus on pseudocapacitive oxide anodes (Nb 2 O 5 , MoO 3 , etc.), which provide a new opportunity to obtain a higher power density of the hybrid devices. The application of Mxene as an anode material of MICs is also discussed. A perspective to the future research of MICs toward practical applications is proposed to close.

A straightforward one-step chemical method to in situ synthesis of Ag nanoparticles (Ag NPs) on single-layer graphene oxide (GO) and reduced graphene oxide (r-GO) surfaces is proposed. After simply heating the single-layer GO or r-GO adsorbed on 3-aminopropyltriethoxysilane (APTES)-modified Si/SiOx substrates in a silver nitrate aqueous solution at 75 °C, Ag NPs are synthesized and grow on the GO or r-GO surface. The obtained Ag NPs are investigated by atomic force microscopy, scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and Raman spectroscopy. Our method is unique and important since no reducing agent is required in the reaction. Au NPs on a GO surface are obtained by simply immersing the obtained Ag NPs on the GO surface in HAuCl4 solution.

Abstract Sodium‐ion batteries (SIBs) are considered as promising alternatives to lithium‐ion batteries owing to the abundant sodium resources. However, the limited energy density, moderate cycling life, and immature manufacture technology of SIBs are the major challenges hindering their practical application. Recently, numerous efforts are devoted to developing novel electrode materials with high specific capacities and long durability. In comparison with carbonaceous materials (e.g., hard carbon), partial Group IVA and VA elements, such as Sn, Sb, and P, possess high theoretical specific capacities for sodium storage based on the alloying reaction mechanism, demonstrating great potential for high‐energy SIBs. In this review, the recent research progress of alloy‐type anodes and their compounds for sodium storage is summarized. Specific efforts to enhance the electrochemical performance of the alloy‐based anode materials are discussed, and the challenges and perspectives regarding these anode materials are proposed.

3D hollow hybrid composites with ultrafine cobalt sulfide nanoparticles uniformly embedded within the well-graphitized porous carbon polyhedra/carbon nanotubes framework are rationally fabricated using a green and one-step method involving the simultaneous pyrolysis and sulfidation of ZIF-67. Because of the synergistic coupling effects favored by the unique nanohybridization, these composites exhibit high specific capacity, excellent cycle stability, and superior rate capability when evaluated as electrodes in lithium-ion batteries. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

A three-dimensional graphene network (3DGN) grown on nickel foam is an excellent template for the synthesis of graphene-based composite electrodes for use in supercapacitors. Ni(OH)2nanosheets coated onto single-crystal Ni3S2nanorods grown on the surface of the 3DGN (referred to as the Ni3S2@Ni(OH)2/3DGN) are synthesized using a one-step hydrothermal reaction. SEM, TEM, XRD and Raman spectroscopy are used to investigate the morphological and structural evolution of the Ni3S2@Ni(OH)2/3DGN. Detailed electrochemical characterization shows that the Ni3S2@Ni(OH)2/3DGN exhibits high specific capacitance (1277 F g−1 at 2 mV s−1 and 1037.5 F g−1 at 5.1 A g−1) and areal capacitance (4.7 F cm−2 at 2 mV s−1 and 3.85 F cm−2 at 19.1 mA cm−2) with good cycling performance (99.1% capacitance retention after 2000 cycles).

Abstract A novel composite, MoS 2 ‐coated three‐dimensional graphene network (3DGN), referred to as MoS 2 /3DGN, is synthesized by a facile CVD method. The 3DGN, composed of interconnected graphene sheets, not only serves as template for the deposition of MoS 2 , but also provides good electrical contact between the current collector and deposited MoS 2 . As a proof of concept, the MoS 2 /3DGN composite, used as an anode material for lithium‐ion batteries, shows excellent electrochemical performance, which exhibits reversible capacities of 877 and 665 mAh g −1 during the 50 th cycle at current densities of 100 and 500 mA g −1 , respectively, indicating its good cycling performance. Furthermore, the MoS 2 /3DGN composite also shows excellent high‐current‐density performance, e.g., depicts a 10 th ‐cycle capacity of 466 mAh g −1 at a high current density of 4 A g −1 .

Intercalation and exfoliation of lithium: Few-layer-thick inorganic nanosheets (BN, NbSe2, WSe2, Sb2Se3, and Bi2Te3) have been prepared from their layered bulk precursors by using a controllable electrochemical lithium intercalation process (see picture). The lithium intercalation conditions, such as cut-off voltage and discharge current, have been systematically studied and optimized to produce high-quality BN and NbSe2 nanosheets.

A 3D hierarchical meso- and macroporous Na3V2(PO4)3-based hybrid cathode with connected Na ion/electron pathways is developed for ultra-fast charge and discharge sodium-ion batteries. It delivers an excellent rate capability (e.g., 86 mA h g−1 at 100 C) and outstanding cycling stability (e.g., 64% retention after 10 000 cycles at 100 C), indicating its superiority in practical applications. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

High symmetric porous Co3O4 hollow dodecahedra constructed by nanometer-sized building blocks are rationally synthesized by templating against Co-containing zeolitic imidazolate framework-67. The well-defined hollow structure and highly porous framework render these hollow dodecahedra exhibit high specific capacity, excellent cycling stability and superior rate capability when evaluated as an anode material for lithium-ion batteries.

Graphene has attracted increasing attention due to its unique electrical, optical, optoelectronic, and mechanical properties, which have opened up huge numbers of opportunities for applications. An overview of the recent research on graphene and its derivatives is presented, with a particular focus on synthesis, properties, and applications in solar cells.

Hollow hierarchical spheres self-organized from the ultrathin nanosheets of α-Fe2O3 were prepared by a simple process. These ultrathin nanosheet subunits possess an average thickness of around 3.5 nm and show preferential exposure of (110) facets. Their Li ion storage and visible-light photocatalytic water oxidation performance are tested. Such hierarchical nanostructures show high Li storage properties with good cycling stability and excellent rate capabilities. The water oxidation catalytic activity is 70 μmol h−1 g−1 for O2 evolution under visible light irradiation and can be maintained for 15 hours. The structural features of these α-Fe2O3 nanocrystals are considered to be important to lead to the attractive properties in both Li storage and photocatalytic water oxidation, e.g. hollow interior, ultrathin thickness and largely exposed active facets.

We demonstrate in this paper facile synthesis of CoS 2 and NiS 2 hollow spheres with various interiors through a solution‐based route. The obtained CoS 2 microspheres constructed by nanosheets display a three‐dimensional architecture with solid, yolk‐shell, double‐shell, and hollow interiors respectively, with continuous changes in specific surface areas and pore‐size distributions. Especially, the CoS 2 hollow spheres demonstrate excellent supercapacitive performance including high specific capacitance, good charge/discharge stability and long‐term cycling life, owing to the greatly improved faradaic redox reaction and mass transfer. Furthermore, CoS 2 hollow spheres exhibit superior electrocatalytic activity for disulfide/thiolate (T 2 /T − ) redox electrolyte in dye‐sensitized solar cells (DSCs). Therefore, this work provides a promising approach for the design and synthesis of structure tunable materials with largely enhanced supercapacitor behavior, which can be potentially applied in energy storage devices.

Reduced graphene oxide-wrapped MoO3M (rGO/MoO3 ) is prepared by a novel and simple method that is developed by using a metal-organic framework as the precursor. After a two-step annealing process, the obtained rGO/MoO3 composite is used for a high-performance supercapacitor electrode. Moreover, an all-solid-state flexible supercapacitor is fabricated based on the rGO/MoO3 composite, which shows stable performance under different bending states.

We demonstrate a facile hydrothermal method for growth of ultrathin NiCo2S4 nanosheets on reduced graphene oxide (RGO), which exhibit remarkable electrochemical performance with higher capacitance and longer cycle life than the bare NiCo2S4 hollow spheres (HSs).

Energy storage and conversion technologies are vital to the efficient utilization of sustainable renewable energy sources. Rechargeable lithium‐ion batteries (LIBs) and the emerging sodium‐ion batteries (SIBs) are considered as two of the most promising energy storage devices, and electrocatalysis processes play critical roles in energy conversion techniques that achieve mutual transformation between renewable electricity and chemical energies. It has been demonstrated that nanostructured metal chalcogenides including metal sulfides and metal selenides show great potential for efficient energy storage and conversion due to their unique physicochemical properties. In this feature article, the recent research progress on nanostructured metal sulfides and metal selenides for application in SIBs/LIBs and hydrogen/oxygen electrocatalysis (hydrogen evolution reaction, oxygen evolution reaction, and oxygen reduction reaction) is summarized and discussed. The corresponding electrochemical mechanisms, critical issues, and effective strategies towards performance improvement are presented. Finally, the remaining challenges and perspectives for the future development of metal chalcogenides in the energy research field are proposed.

Over the past three decades, intensive research activities have focused on the development of electrochemical energy storage devices, particularly exploiting the concept of flow batteries. Amongst these, vanadium redox flow batteries (VRFB) are an attractive option, which have been studied extensively and are now being commercialized around the world. The performance of the VRFB system is governed by several critical components namely the electrolyte, the electrode, the ion‐exchange membrane and the flow field design. Here, the focus is mainly on recent research activities relating to the development and modification of electrode materials and new ion‐exchange membranes. The feasibility of novel flow field designs for high energy density VRFB systems and their future prospects are also discussed in detail.

Ultrathin metal sulphide nanomaterials exhibit many unique properties, and are thus attractive materials for numerous applications. However, the high-yield, large-scale synthesis of well-defined ultrathin metal sulphide nanostructures by a general and facile wet-chemical method is yet to be realized. Here we report a universal soft colloidal templating strategy for the synthesis of high-quality ultrathin metal sulphide nanocrystals, that is 3.2 nm-thick hexagonal CuS nanosheets, 1.8 nm-diameter hexagonal ZnS nanowires, 1.2 nm-diameter orthorhombic Bi(2)S(3) nanowires and 1.8 nm-diameter orthorhombic Sb(2)S(3) nanowires. As a proof of concept, the ultrathin CuS nanosheets are used to fabricate an electrode for a lithium-ion battery, which exhibits a large capacity and good cycling stability, even after 360 cycles. Furthermore, high-yield, gram-scale production of these ultrathin metal sulphide nanomaterials has been achieved (~100%, without size-sorting process). Our method could be broadly applicable for the high-yield production of novel ultrathin nanostructures with great promise for various applications.

Sodium-ion batteries (SIBs) are still confronted with several major challenges, including low energy and power densities, short-term cycle life, and poor low-temperature performance, which severely hinder their practical applications. Here, a high-voltage cathode composed of Na3 V2 (PO4 )2 O2 F nano-tetraprisms (NVPF-NTP) is proposed to enhance the energy density of SIBs. The prepared NVPF-NTP exhibits two high working plateaux at about 4.01 and 3.60 V versus the Na+ /Na with a specific capacity of 127.8 mA h g-1 . The energy density of NVPF-NTP reaches up to 486 W h kg-1 , which is higher than the majority of other cathode materials previously reported for SIBs. Moreover, due to the low strain (≈2.56% volumetric variation) and superior Na transport kinetics in Na intercalation/extraction processes, as demonstrated by in situ X-ray diffraction, galvanostatic intermittent titration technique, and cyclic voltammetry at varied scan rates, the NVPF-NTP shows long-term cycle life, superior low-temperature performance, and outstanding high-rate capabilities. The comparison of Ragone plots further discloses that NVPF-NTP presents the best power performance among the state-of-the-art cathode materials for SIBs. More importantly, when coupled with an Sb-based anode, the fabricated sodium-ion full-cells also exhibit excellent rate and cycling performances, thus providing a preview of their practical application.

We report a simple wet-chemical process to prepare porous CuO nanobelts (NBs) with high surface area and small crystal grains. These CuO NBs were mixed with carbon nanotubes in an appropriate ratio to fabricate pseudocapacitor electrodes with stable cycling performances, which showed a series of high energy densities at different power densities, for example, 130.2, 92, 44, 25, and 20.8 W h kg−1 at power densities of 1.25, 6.25, 25, and 50 k Wh kg−1, respectively. CuO-on-single-walled carbon nanotube (SWCNT) flexible hybrid electrodes were also fabricated using the SWCNT films as current collectors. These flexible electrodes showed much higher specific capacitance than that of electrodes made of pure SWCNTs and exhibited more stable cycling performance, for example, effective specific capacitances of >62 F g−1 for the hybrid electrodes after 1000 cycles in 1 M LiPF6/EC:DEC at a current density of 5 A g−1 and specific capacitance of only 23.6 F g−1 for pure SWCNT electrodes under the same testing condition.

Lithium‐ion capacitors (LICs) are hybrid energy storage devices that have the potential to bridge the gap between conventional high‐energy lithium‐ion batteries and high‐power capacitors by combining their complementary features. The challenge for LICs has been to improve the energy storage at high charge−discharge rates by circumventing the discrepancy in kinetics between the intercalation anode and capacitive cathode. In this article, the rational design of new nanostructured LIC electrodes that both exhibit a dominating capacitive mechanism (both double layer and pseudocapacitive) with a diminished intercalation process, is reported. Specifically, the electrodes are a 3D interconnected TiC nanoparticle chain anode, synthesized by carbothermal conversion of graphene/TiO 2 hybrid aerogels, and a pyridine‐derived hierarchical porous nitrogen‐doped carbon (PHPNC) cathode. Electrochemical properties of both electrodes are thoroughly characterized which demonstrate their outstanding high‐rate capabilities. The fully assembled PHPNC//TiC LIC device delivers an energy density of 101.5 Wh kg −1 and a power density of 67.5 kW kg −1 (achieved at 23.4 Wh kg −1 ), and a reasonably good cycle stability (≈82% retention after 5000 cycles) within the voltage range of 0.0−4.5 V.

Abstract Uniform Ni 3 C nanodots dispersed in ultrathin N‐doped carbon nanosheets were successfully prepared by carburization of the two dimensional (2D) nickel cyanide coordination polymer precursors. The Ni 3 C based nanosheets have lateral length of about 200 nm and thickness of 10 nm. When doped with Fe, the Ni 3 C based nanosheets exhibited outstanding electrocatalytic properties for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). For example, 2 at % Fe (atomic percent) doped Ni 3 C nanosheets depict a low overpotential (292 mV) and a small Tafel slope (41.3 mV dec −1 ) for HER in KOH solution. An outstanding OER catalytic property is also achieved with a low overpotential of 275 mV and a small Tafel slope of 62 mV dec −1 in KOH solution. Such nanodot‐incorporated 2D hybrid structures can serve as an efficient bifunctional electrocatalyst for overall water splitting.

We report the synthesis of ultrathin S-doped MoSe2 nanosheets demonstrating enhanced HER catalysis with a low onset overpotential of 90 mV and a Tafel slope of 58 mV per decade. We attribute the improved catalytic effects to the proliferation of unsaturated HER active sites in MoSe2 resulting from S-doping.

Abstract Herein, the hydrothermal synthesis of porous ultrathin ternary NiFeV layer double hydroxides (LDHs) nanosheets grown on Nickel foam (NF) substrate as a highly efficient electrode toward overall water splitting in alkaline media is reported. The lateral size of the nanosheets is about a few hundreds of nanometers with the thickness of ≈10 nm. Among all molar ratios investigated, the Ni 0.75 Fe 0.125 V 0.125 ‐LDHs/NF electrode depicts the optimized performance. It displays an excellent catalytic activity with a modest overpotential of 231 mV for the oxygen evolution reaction (OER) and 125 mV for the hydrogen evolution reaction (HER) in 1.0 m KOH electrolyte. Its exceptional activity is further shown in its small Tafel slope of 39.4 and 62.0 mV dec −1 for OER and HER, respectively. More importantly, remarkable durability and stability are also observed. When used for overall water splitting, the Ni 0.75 Fe 0.125 V 0.125 ‐LDHs/NF electrodes require a voltage of only 1.591 V to reach 10 mA cm −2 in alkaline solution. These outstanding performances are mainly attributed to the synergistic effect of the ternary metal system that boosts the intrinsic catalytic activity and active surface area. This work explores a promising way to achieve the optimal inexpensive Ni‐based hydroxide electrocatalyst for overall water splitting.

Abstract A simple method for the preparation of metal‐oxide‐coated three‐dimensional (3D) graphene composites was developed. The metal–organic frameworks (MOFs) that served as the precursors of the metal oxides were first synthesized on the 3D graphene networks (3DGNs). The desired metal oxide/3DGN composites were then obtained by a two‐step annealing process. As a proof‐of‐concept application, the obtained ZnO/3DGN and Fe 2 O 3 /3DGN materials were used in a photocatalytic reaction and a lithium‐ion battery, respectively. We believe this method could be extended to the synthesis of other metal oxide/3DGN composites with 3D structures simply through the appropriate choice of specific MOFs as precursors.

Thermoelectric materials can be potentially employed in solid-state devices that harvest waste heat and convert it to electrical power, thereby improving the efficiency of fuel utilization. The spectacular increases in the efficiencies of these materials achieved over the past decade have raised expectations regarding the use of thermoelectric generators in various energy saving and energy management applications, especially at mid to high temperature (400-900 °C). However, several important issues that prevent successful thermoelectric generator commercialization remain unresolved, in good part because of the lack of a research roadmap.

The conversion of carbon dioxide (CO2) into fuels and valuable chemicals using solar energy is a promising method for reducing CO2 emissions and solving energy supply issues. However, the development of inexpensive, efficient and metal-free materials for photocatalytic CO2 reduction is challenging. Herein, we report a facile supramolecular self-assembly strategy for the preparation of porous nitrogen-rich graphitic carbon nitride (g-C3N4) nanotubes with Lewis basicity and a large surface area, which are beneficial for the adsorption of CO2 and, consequently, the enhancement of the photocatalytic CO2 reduction activity. The metal-free porous nitrogen-rich g-C3N4 nanotubes catalyst exhibits a superior visible-light-induced CO2-to-CO conversion rate of 103.6 μmol g−1 h−1, which is 17 and 15 times higher than those of bulk g-C3N4 (6.1 μmol g−1 h−1) and P25-TiO2 (7.1 μmol g−1 h−1), respectively, and exceeds the performance of most metal-free photocatalysts. This work provides new insights into the synthesis of functional groups-modified g-C3N4 with a unique structure for effective photocatalytic CO2 reduction.

The principal challenges facing the development of lithium ion batteries (LIBs) for hybrid electric/plug-in-hybrid (HEV/PHEV) vehicles and for off-peak energy storage are cost, safety, cell energy density (voltage × capacity), rate of charge/discharge, and service life. There are exciting developments in new positive electrode (cathode) materials to replace the LiCoO2 for use in the LIBs over the past decade. Monoclinic Li3V2(PO4)3 (LVP) with promising electrochemical properties including excellent cycling stability, high theoretical capacity (197 mAh g−1), low synthetic cost, improved safety characteristic, and low environmental impact emerges as highly suitable candidate. In this review, we focus on research work related to the LVP and discuss its host structure, mechanism of lithium insertion/extraction, transport properties (i.e., electronic conductivity, and lithium diffusion), synthesis and electrochemical properties. We highlight some recent development of LVP, which shows superior cycling stability and high rate capability and give some vision for the future research of LVP based electrodes.

Metallic-like transition metal-based nanostructures (MLTMNs) has recently arisen as robust and highly efficient materials for energy storage and conversion. Owning to extraordinary advantages over the semiconducting/insulating ones (in terms of fast reaction kinetics, rapid electrical transport, and intrinsically high activity) combined with the high natural abundance, this class of materials is progressively developed towards commercial applications in real energy technologies. This review summarizes and discusses the progress in energy storages and conversions that employ MLTMNs. After the introduction and fundamental characteristics, developments in synthetic methodologies of MLTMNs and its application in energy storage and conversion are provided with more attention on strategies to improve electrochemical performances. Personal outlook on the challenges and opportunities of MLTMNs for industrial applications in real energy technologies are proposed and discussed in the conclusion.

Abstract Flexible three‐dimensional (3D) nanoarchitectures have received tremendous interest recently because of their potential applications in wearable electronics, roll‐up displays, and other devices. The design and fabrication of a flexible and robust electrode based on cobalt sulfide/reduced graphene oxide/carbon nanotube (CoS 2 /RGO‐CNT) nanocomposites are reported. An efficient hydrothermal process combined with vacuum filtration was used to synthesize such composite architecture, which was then embedded in a porous CNT network. This conductive and robust film is evaluated as electrocatalyst for the hydrogen evolution reaction. The synergistic effect of CoS 2 , graphene, and CNTs leads to unique CoS 2 /RGO‐CNT nanoarchitectures, the HER activity of which is among the highest for non‐noble metal electrocatalysts, showing 10 mA cm −2 current density at about 142 mV overpotentials and a high electrochemical stability.

N anoparticles of n-type conjugated ladder polymer poly(benzobisimidazobenzo­phenanthroline) (BBL) and its analogue (SBBL) are prepared through a reprecipitation method. The ladder polymers are tested as anode materials for lithium-ion batteries for the first time. They exhibit high capacity, good rate performance, and excellent cycle life, especially at high temperature of 50 °C.

We demonstrate a simple, efficient, yet versatile method for the realization of core–shell assembly of graphene around various metal oxide (MO) nanostructures, including nanowires (NWs) and nanoparticles (NPs). The process is driven by (i) the ring-opening reaction between the epoxy groups and amine groups in graphene oxide (GO) platelets and amine-modified MO nanostructures, respectively, and (ii) electrostatic interaction between these two components. Nearly every single NW or NP is observed to be wrapped by graphene. To the best of our knowledge, this is the first report that substrate-supported MO NWs are fully coated with a graphene shell. As an example of the functional properties of these compound materials, the graphene@α-Fe2O3 core–shell NPs are investigated as the lithium-ion battery (LIB) electrode, which show a high reversible capacity, improved cycling stability, and excellent rate capability with respect to the pristine α-Fe2O3. The superior performance of the composite electrode is presumably attributed to the effectiveness of the graphene shell in preventing the aggregation, buffering the volume change, maintaining the integrity of NPs, as well as improving the conductivity of the electrode.

Sodium-ion batteries (SIBs) are considered as complementary alternatives to lithium-ion batteries for grid energy storage due to the abundance of sodium. However, low capacity, poor rate capability, and cycling stability of existing anodes significantly hinder the practical applications of SIBs. Herein, ultrathin two-dimensional SnS2 nanosheets (3–4 nm in thickness) are synthesized via a facile refluxing process toward enhanced sodium storage. The SnS2 nanosheets exhibit a high apparent diffusion coefficient of Na+ and fast sodiation/desodiation reaction kinetics. In half-cells, the nanosheets deliver a high reversible capacity of 733 mAh g–1 at 0.1 A g–1, which still remains up to 435 mAh g–1 at 2 A g–1. The cell has a high capacity retention of 647 mA h g–1 during the 50th cycle at 0.1 A g–1, which is by far the best for SnS2, suggesting that nanosheet morphology is beneficial to improve cycling stability in addition to rate capability. The SnS2 nanosheets also show encouraging performance in a full cell with a Na3V2(PO4)3 cathode. In addition, the sodium storage mechanism is investigated by ex situ XRD coupled with high-resolution TEM. The high specific capacity, good rate capability, and cycling durability suggest that SnS2 nanosheets have great potential working as anodes for high-performance SIBs.

Transition metal sulfides gain much attention as electrode materials for supercapacitors due to their rich redox chemistry and high electrical conductivity. Designing hierarchical nanostructures is an efficient approach to fully utilize merits of each component. In this work, amorphous MoS 2 is firstly demonstrated to show specific capacitance 1.6 times as that of the crystalline counterpart. Then, crystalline core@amorphous shell (Ni 3 S 4 @MoS 2 ) is prepared by a facile one‐pot process. The diameter of the core and the thickness of the shell can be independently tuned. Taking advantages of flexible protection of amorphous shell and high capacitance of the conductive core, Ni 3 S 4 @amorphous MoS 2 nanospheres are tested as supercapacitor electrodes, which exhibit high specific capacitance of 1440.9 F g −1 at 2 A g −1 and a good capacitance retention of 90.7% after 3000 cycles at 10 A g −1 . This design of crystalline core@amorphous shell architecture may open up new strategies for synthesizing promising electrode materials for supercapacitors.

According to the evidence from both theoretical calculations and experimental findings, conjugated ladder polymers containing large π-conjugated structure, a high number of nitrogen heteroatoms, and a multiring aromatic system, could be an ideal organic anode candidate for lithium-ion batteries (LIBs). In this report, we demonstrated that the nanostructured polyazaacene analogue poly(1,6-dihydropyrazino[2,3g]quinoxaline-2,3,8-triyl-7-(2H)-ylidene-7,8-dimethylidene) (PQL) shows high performance as anode materials in LIBs: high capacity (1750 mAh g(-1), 0.05C), good rate performance (303 mAh g(-1), 5C), and excellent cycle life (1000 cycles), especially at high temperature of 50 °C. Our results suggest nanostructured conjugated ladder polymers could be alternative electrode materials for the practical application of LIBs.

3D hierarchical hollow nanocubes constructed by 1D FeSe2@C core-shell nanorods were successfully prepared by a thermally-induced selenization process of their Prussian blue microcubes precursor. Such novel nanorods-based FeSe2@C hollow structures exhibit high conductivity and special structural property which provide good charge transport kinetics by facilitating the charge transfer into the inner of FeSe2 nanorods. When used as anode materials for sodium ion batteries, the hierarchically hollow nanocubes showed excellent rate performance and ultra-stable long-term cycling stability at a high current density of 10 A g−1, suggesting a good sodium-ion storage material. This simple solid-phase process demonstrated in this work can be further used for the preparation of other metal selenide with unique and fascinating structure for the potential applications in the energy storage field.

Phosphorus‐based materials are promising for high‐performance lithium‐ion battery (LIB) applications due to their high theoretical specific capacity. Currently, the existing physical methods render great difficulty toward rational engineering on the nanostructural phosphorus or its composites, thus limiting its high‐rate LIB applications. For the first time, a sublimation‐induced synthesis of phosphorus‐based composite nanosheets by a chemistry‐based solvothermal reaction is reported. Its formation mechanism involves solid–vapor–solid transformation driven by continuous vaporization–condensation process, as well as subsequent bottom‐up assembly growth. The proof‐of‐concept LIBs composed of the phosphorus‐based nanosheets achieve a high capacity of 630 mAh g −1 at an ultrahigh current density of 20 A g −1 , which is attributed to efficient lithium‐ion diffusion and electron transfer. Such simple sublimation‐induced transformation opens up new prospects for rational engineering of phosphorus‐based materials for enhancing electrochemical performance.

Olivine-type LiMPO4 (M = Fe, Mn, Co, Ni) has become of great interest as cathodes for next-generation high-power lithium-ion batteries. Nevertheless, this family of compounds suffers from poor electronic conductivities and sluggish lithium diffusion in the [010] direction. Here, we develop a liquid-phase exfoliation approach combined with a solvothermal lithiation process in high-pressure high-temperature (HPHT) supercritical fluids for the fabrication of ultrathin LiMPO4 nanosheets (thickness: 3.7–4.6 nm) with exposed (010) surface facets. Importantly, the HPHT solvothermal lithiation could produce monodisperse nanosheets while the traditional high-temperature calcination, which is necessary for cathode materials based on high-quality crystals, leads the formation of large grains and aggregation of the nanosheets. The as-synthesized nanosheets have features of high contact area with the electrolyte and fast lithium transport (time diffusion constant in at the microsecond level). The estimated diffusion time for Li+ to diffuse over a [010]-thickness of <5 nm (L) was calculated to be less than 25, 2.5, and 250 μs for LiFePO4, LiMnPO4, and LiCoPO4 nanosheets, respectively, via the equation of t = L2/D. These values are about 5 orders of magnitude lower than the corresponding bulk materials. This results in high energy densities and excellent rate capabilities (e.g., 18 kW kg–1 and 90 Wh kg–1 at a 80 C rate for LiFePO4 nanosheets).

Rechargeable aqueous zinc-ion batteries (ZIBs) featured with environmental friendliness, low cost, and high safety have attracted great interest but still suffer from the lack of high-performance electrodes. Herein, a facile in situ approach is developed to simultaneously introduce multivalence, increase the interlayer water content, and expand the interlayer distance in hydrated V2O5. These structural modulations endow the as-obtained layer-expanded V2O5 2.2H2O (E-VO) nanosheets with faster charge transfer kinetics, more Zn2+ storage space, and higher structural stability than precursor V2O5. Besides, a unique flexible Zn/stainless steel (Zn/SS) mesh composite anode with low polarization and uniform Zn stripping/plating behavior is fabricated, which alleviates the Zn dendrite growth. As cathode for aqueous ZIBs, E-VO exhibits high reversible capacity (450 mAh g−1 at 0.1 A g−1), good rate capability (222 mAh g−1 at 10 A g−1) and long stability (72% capacity retention for 3000 cycles at 5 A g−1). Moreover, the flexibility and large lateral size make E-VO a high-performance binder-free cathode for flexible quasi-solid-state Zn/E-VO battery, i.e. high capacity under different bending states (361 mAh g−1 at 0.1 A g−1), good rate capability (115 mAh g−1 at 2 A g−1), and long stability (85% capacity retention for 300 cycles at 1 A g−1). The achievements of this study can be considered as an important step toward the development of aqueous-based ZIBs.

The recent advances and new insights resulting thereof in applying defect engineering to improving the thermoelectric performance and mechanical properties of inorganic materials are reviewed.

Abstract Herein, the authors present the development of novel 0D–2D nanohybrids consisting of a nickel‐based bimetal phosphorus trisulfide (Ni 1− x Fe x PS 3 ) nanomosaic that decorates on the surface of MXene nanosheets (denoted as NFPS@MXene). The nanohybrids are obtained through a facile self‐assemble process of transition metal layered double hydroxide (TMLDH) on MXene surface; followed by a low temperature in situ solid‐state reaction step. By tuning the Ni:Fe ratio, the as‐synthesized NFPS@MXene nanohybrids exhibit excellent activities when tested as electrocatalysts for overall water splitting. Particularly, with the initial Ni:Fe ratio of 7:3, the obtained Ni 0.7 Fe 0.3 PS 3 @MXene nanohybrid reveals low overpotential (282 mV) and Tafel slope (36.5 mV dec −1 ) for oxygen evolution reaction (OER) in 1 m KOH solution. Meanwhile, the Ni 0.9 Fe 0.1 PS 3 @MXene shows low overpotential (196 mV) for the hydrogen evolution reaction (HER) in 1 m KOH solution. When integrated for overall water splitting, the Ni 0.7 Fe 0.3 PS 3 @MXene || Ni 0.9 Fe 0.1 PS 3 @MXene couple shows a low onset potential of 1.42 V and needs only 1.65 V to reach a current density of 10 mA cm −2 , which is better than the all noble metal IrO 2 || Pt/C electrocatalyst (1.71 mV@10 mA cm −2 ). Given the chemical versatility of Ni 1− x Fe x PS 3 and the convenient self‐assemble process, the nanohybrids demonstrated in this work are promising for energy conversion applications.

Molecularly well-defined Ni sites at heterogeneous interfaces were derived from the incorporation of Ni2+ ions into heteroatom-doped graphene. The molecular Ni sites on graphene were redox-active. However, they showed poor activity toward oxygen evolution reaction (OER) in KOH aqueous solution. We demonstrated for the first time that the presence of Fe3+ ions in the solution could bond at the vicinity of the Ni sites with a distance of 2.7 Å, generating molecularly sized and heterogeneous Ni-Fe sites anchored on doped graphene. These Ni-Fe sites exhibited markedly improved OER activity. The Pourbaix diagram confirmed the formation of the Ni-Fe sites and revealed that the Ni-Fe sites adsorbed HO- ions with a bridge geometry, which facilitated the OER electrocatalysis.

Abstract In recent years, the rapidly growing attention on MXenes makes the material a rising star in the 2D materials family. Although most researchers' interests are still focused on the properties of bare MXenes, little attention has been paid to the surface chemistry of MXenes and MXene‐based nanocomposites. To this end, this Review offers a comprehensive discussion on surface modified MXene‐based nanocomposites for energy conversion and storage (ECS) applications. Based on the structure and reaction mechanism, the related synthesis methods toward MXenes are briefly summarized. After the discussion of existing surface modification techniques, the surface modified MXene‐based nanocomposites and their inherent chemical principles are presented. Finally, the application of these surface modified nanocomposites for supercapacitors (SCs), lithium/sodium–ion batteries (LIBs/SIBs), and electrocatalytic water splitting is discussed. The challenges and prospects of MXene‐based nanocomposites for future ECS applications are also presented.

Abstract Flexible three‐dimensional (3D) nanoarchitectures have received tremendous interest recently because of their potential applications in wearable electronics, roll‐up displays, and other devices. The design and fabrication of a flexible and robust electrode based on cobalt sulfide/reduced graphene oxide/carbon nanotube (CoS 2 /RGO‐CNT) nanocomposites are reported. An efficient hydrothermal process combined with vacuum filtration was used to synthesize such composite architecture, which was then embedded in a porous CNT network. This conductive and robust film is evaluated as electrocatalyst for the hydrogen evolution reaction. The synergistic effect of CoS 2 , graphene, and CNTs leads to unique CoS 2 /RGO‐CNT nanoarchitectures, the HER activity of which is among the highest for non‐noble metal electrocatalysts, showing 10 mA cm −2 current density at about 142 mV overpotentials and a high electrochemical stability.

A large-area, continuous, few-layer reduced graphene oxide (rGO) thin film has been fabricated on a Si/SiO2 wafer using the Langmuir–Blodgett (LB) method followed by thermal reduction. After photochemical reduction of Pt nanoparticles (PtNPs) on rGO, the obtained PtNPs/rGO composite is employed as the conductive channel in a solution-gated field effect transistor (FET), which is then used for real-time detection of hybridization of single-stranded DNA (ssDNA) with high sensitivity (2.4 nM). Such a simple, but effective method for fabrication of rGO-based transistors shows great potential for mass-production of graphene-based electronic biosensors.

A facile and bottom-up approach has been presented to prepare 2D Ni-MOFs based on cyanide-bridged hybrid coordination polymers. After thermally induced sulfurization and selenization processes, Ni-MOFs were successfully converted into NiS and NiSe2 nanoplates with carbon coating due to the decomposition of its organic parts. When evaluated as anodes of Li-ion batteries (LIBs) and Na-ion batteries (NIBs), NiS and NiSe2 nanoplates show high specific capacities, excellent rate capabilities, and stable cycling stability. The NiS plates show good Li storage properties, while NiSe2 plates show good Na storage properties as anode materials. The study of the diffusivity of Li+ in NiS and Na+ in NiSe2 shows consistent results with their Li/Na storage properties. The 2D MOFs-derived NiS and NiSe2 nanoplates reported in this work explore a new approach for the large-scale synthesis of 2D metal sulfides or selenides with potential applications for advanced energy storage.

Among the various energy solutions, lithium‐ion batteries (LIBs) play an important role in the process of the transition from fossil fuels to renewables. However, the necessity to replace lithium with cheaper alternatives due to its scarcity has recently attracted great interest to developing sodium‐ion batteries (SIBs). Hence, the discovery and development of suitable cathode materials that exhibit high specific capacity, good cycling stability, and high energy density are actively pursued. Today's SIB technology continues to be driven by the performance of the cathode materials. Here, recent advancements made regarding the cathode of SIBs are summarized, covering some of the fundamental aspects of SIBs, synthetic protocols, and characteristics of existing and prospective cathode materials used for SIBs. Furthermore, some of the latest achievements in the fabrication of cathode materials, as a practical demonstration on their viability, are also discussed. With better understanding of these topics, the rationales behind their enhanced electrochemical performances are revealed and explained. Last but not least, imminent challenges and future prospects are also included to provide some insights into the possible development of advanced cathode materials for SIBs.

Few-layered Ni(OH)2 nanosheets (4–5 nm in thickness) are synthesized towards high-performance supercapacitors. The ultrathin Ni(OH)2 nanosheets show high specific capacitance and good rate capability in both three-electrode and asymmetric devices. In the three-electrode device, the Ni(OH)2 nanosheets deliver a high capacitance of 2064 F g−1 at 2 A g−1, and the capacitance still has a retention of 1837 F g−1 at a high current density of 20 A g−1. Such excellent performance is by far one of the best for Ni(OH)2 electrodes. In the two-electrode asymmetric device, the specific capacitance is 248 F g−1 at 1 A g−1, and reaches 113 F g−1 at 20 A g−1. The capacitance of the asymmetric device maintains to be 166 F g−1 during the 4000th cycle at 2 A g−1, suggesting good cycling stability of the device. Besides, the asymmetric device exhibits gravimetric energy density of 22 Wh kg−1 at a power density of 0.8 kW kg−1. The present results demonstrate that the ultrathin Ni(OH)2 nanosheets are highly attractive electrode materials for achieving fast charging/discharging and high-capacity supercapacitors.

A NiCo₂O₄/NiO-HD nanocage is synthesized using MOF as a precursor and self-sacrificing template. A lithium-ion battery anode based this novel nanomaterial exhibits outstanding capacity, cycling stability and rate performance.

Heterostructures with abundant phase boundaries are compelling for surface-mediated electrochemical applications. However, rational design of such bifunctional electrocatalysts for efficient hydrogen and oxygen evolution reactions (HER and OER) is still challenging. Here, due to the well-matched lattice parameters, we easily achieved the epitaxy of two-dimensional ternary nickel thiophosphate (NiPS3) nanosheets with in-grown dinickel phosphide (Ni2P) through an in situ growth strategy. Density functional theory calculations reveal that the NiPS3/Ni2P heterojunction significantly decreases the kinetic barrier for hydrogen adsorption and accelerates electron transfer due to the built-in electric field at the epitaxial interfaces. The significantly improved electrocatalytic performance is shown to be closely related to the epitaxial interfacial area rather than the amount of secondary phase. Notably, the resultant NiPS3/Ni2P heterostructures enable an overall water splitting electrolyzer to achieve 50 mA cm–2 at a lower bias of 1.65 V compared to that for the pristine NiPS3 alone (2.02 V) and even the benchmark Pt/C//IrO2 electrocatalysts (1.69 V).

A facile, environmentally friendly, and economical synthetic route for production of large-amounts (gram scale) of two-dimensional (2D) layered SnS2 nanoplates is presented. The electrode fabricated from the SnS2 nanoplate exhibits excellent lithium-ion battery performance with highly reversible capacity, good cycling stability and excellent capacity retention after 30 cycles.

Phosphorene, monolayer or few‐layer black phosphorus (BP), has recently triggered strong scientific interest for lithium/sodium ion batteries (LIBs/SIBs) applications. However, there are still challenges regarding large‐scale fabrication, poor air stability. Herein, we report the high‐yield synthesis of phosphorene with good crystallinity and tunable size distributions via liquid‐phase exfoliation of bulk BP in formamide. Afterwards, a densely packed phosphorene–graphene composite (PG‐SPS, a packing density of 0.6 g cm −3 ) is prepared by a simple and easily up‐scalable spark plasma sintering (SPS) process. When working as anode materials of LIBs, PG‐SPS exhibit much improved first‐cycle Coloumbic efficiency (60.2%) compared to phosphorene (11.5%) and loosely stacked phosphorene–graphene composite (34.3%), high specific capacity (1306.7 mAh g −1 ) and volumetric capacity (256.4 mAh cm −3 ), good rate capabilities (e.g., 415.0 mAh g −1 at 10 A g −1 ) as well as outstanding long‐term cycling life (91.9% retention after 800 cycles at 10 A g −1 ). Importantly, excellent air stability of PG‐SPS over the 60 days observation in maintaining its high Li storage properties can be achieved. On the contrary, 95.2% of BP in PG sample was oxidized after only 10 days exposure to ambience, leading to severe degradation of electrochemical properties.

Nitrogen and sulfur dual-doped Mo2 C nanosheets provide low operating potential (-86 mV for driving 10 mA cm(-2) of current density). Co-doping of N and S heteroatoms can improve the wetting property of the Mo2C electrocatalyst in aqueous solution and induce synergistic effects via σ-donation and π-back donation with hydronium cation.

The electrochemical performance of the as-synthesized mesoporous NiCo₂O₄ flower-like products as electrode materials for battery-type supercapacitors is systematically investigated in detail.

Graphene incorporation should be one effective strategy to develop advanced electrode materials for a sodium-ion battery (SIB). Herein, the micro/nanostructural Sb/graphene composite (Sb-O-G) is successfully prepared with the uniform Sb nanospheres (∼100 nm) bound on the graphene via oxygen bonds. It is revealed that the in-situ-constructed oxygen bonds play a significant role on enhancing Na-storage properties, especially the ultrafast charge/discharge capability. The oxygen-bond-enhanced Sb-O-G composite can deliver a high capacity of 220 mAh/g at an ultrahigh current density of 12 A/g, which is obviously superior to the similar Sb/G composite (130 mAh/g at 10 A/g) just without Sb-O-C bonds. It also exhibits the highest Na-storage capacity compared to Sb/G and pure Sb nanoparticles as well as the best cycling performance. More importantly, this Sb-O-G anode achieves ultrafast (120 C) energy storage in SIB full cells, which have already been shown to power a 26-bulb array and calculator. All of these superior performances originate from the structural stability of Sb-O-C bonds during Na uptake/release, which has been verified by ex situ X-ray photoelectron spectroscopies and infrared spectroscopies.

Oxygen vacancy (VO), the most common type of defect in metal oxides, could alter intrinsic properties which are usually determined by crystal structures. Oxygen-deficient metal oxides with regulated properties have been applied in many aspects, especially lithium/sodium-ion batteries and supercapacitors, in which the VO-induced mobility, conductivity, and structural stability could affect their performance to a great extent. By modeling certain oxygen-deficient metal oxides, the mechanisms behind such performance regulations are comprehensively described. For instance, while appropriate VO can enhance the electrochemical properties of anode materials by providing extra active sites, built-in electric field, etc.; the influences of oxygen non-stoichiometry vary with the cathode’s crystal structure and cationic composition. In addition to these, the synthesis strategies and common physical characterization techniques for VO are also introduced. This review aims to introduce oxygen defect chemistry and propel its reasonable applications in the field of electrochemical energy storage.

Multifunctional MoS2 @PANI (polyaniline) pseudo-supercapacitor electrodes consisting of MoS2 thin nanosheets and PANI nanoarrays are fabricated via a large-scale approach. The superior capacitance retention is retained up to 91% after 4000 cycles and a high energy density of 106 Wh kg(-1) is delivered at a power density of 106 kW kg(-1) .

Electrocatalysts are one of the most important parts for oxygen evolution reaction (OER) to overcome the sluggish kinetics. Herein, amorphous Fe-Ni-P-B-O (FNPBO) nanocages as efficient OER catalysts are synthesized by a simple low-cost and scalable method at room temperature. The samples are chemically stable, in clear contrast to reported unstable or even pyrophoric boride samples. The Fe/Ni ratio of the FNPBO nanocages can be continuously adjusted to optimize the OER catalytic performance. The FNPBO nanocages composed of multicomponent elements can weaken the metal-metal bonds, thus rearranging the electron density around the catalytic metal atom centers and reducing the energy barrier for intermediate formation. Hence the optimized FNPBO (Fe6.4Ni16.1P12.9B4.3O60.2) catalyst shows superior intrinsic electrocatalytic activity for OER. The low overpotential to afford the current density of 10 mA cm-2 (236 mV), the small Tafel slope (39 mV dec-1), and the high specific current density (26.44 mA cm-2) at a given overpotential of 300 mV make a sharp contrast to state-of-the-art RuO2 (327 mV, 136 mV dec-1, and 0.028 mA cm-2, respectively).

0D transition metal phosphides (TMPs) nanocrystals (NCs)–2D ultrathin black phosphorus (BP) heterostructure (Ni 2 P@BP) have been synthesized via a facile sonication‐assisted exfoliation followed by a solvothermal process. Compared with the bare BP, the specially designed Ni 2 P@BP architecture can enhance the electrical conductivity (from 2.12 × 10 2 to 6.25 × 10 4 S m –1 ), tune the charge carrier concentration (from 1.25 × 10 17 to 1.37 × 10 20 cm –3 ), and reduce the thermal conductivity (from 44.5 to 7.69 W m –1 K –1 ) at 300 K, which can be considered for multiple applications. As a result, the Ni 2 P@BP exhibits excellent Li storage properties and high hydrogen evolution reaction electrocatalytic activities. The Ni 2 P@BP shows improved Li diffusion kinetics (e.g., the Li ions diffusion coefficient increases from 1.14 × 10 –14 cm 2 s –1 for pure BP nanosheets to 8.02 × 10 –13 cm 2 s –1 for Ni 2 P@BP). In addition, the Ni 2 P@BP electrode sustains hydrogen production with almost unchanged activity over 3000 cycles, which indicates its good chemical stability when operating under strong reducing environment.

SmallVolume 13, Issue 28 1700661 Review 2D Black Phosphorus for Energy Storage and Thermoelectric Applications Yu Zhang, Yu Zhang School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore Energy Research Institute (ERI@N), Interdisciplinary Graduate School, Nanyang Technological University, 50 Nanyang Drive, Singapore, 637553 SingaporeSearch for more papers by this authorYun Zheng, Yun Zheng School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 SingaporeSearch for more papers by this authorKun Rui, Kun Rui Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University (NanjingTech), 2100 Nanjing, ChinaSearch for more papers by this authorHuey Hoon Hng, Huey Hoon Hng School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 SingaporeSearch for more papers by this authorKedar Hippalgaonkar, Kedar Hippalgaonkar Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Innovis #08-03, Singapore, 138634 SingaporeSearch for more papers by this authorJianwei Xu, Jianwei Xu Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Innovis #08-03, Singapore, 138634 SingaporeSearch for more papers by this authorWenping Sun, Wenping Sun Institute for Superconducting and Electronic Materials, Australian Institute for, Innovative Materials, University of Wollongong, NSW, 2522 AustraliaSearch for more papers by this authorJixin Zhu, Corresponding Author Jixin Zhu iamjxzhu@njtech.edu.cn Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University (NanjingTech), 2100 Nanjing, ChinaE-mail: iamjxzhu@njtech.edu.cn, alexyan@ntu.edu.sgSearch for more papers by this authorQingyu Yan, Corresponding Author Qingyu Yan alexyan@ntu.edu.sg School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore Energy Research Institute (ERI@N), Interdisciplinary Graduate School, Nanyang Technological University, 50 Nanyang Drive, Singapore, 637553 SingaporeE-mail: iamjxzhu@njtech.edu.cn, alexyan@ntu.edu.sgSearch for more papers by this authorWei Huang, Wei Huang Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University (NanjingTech), 2100 Nanjing, ChinaSearch for more papers by this author Yu Zhang, Yu Zhang School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore Energy Research Institute (ERI@N), Interdisciplinary Graduate School, Nanyang Technological University, 50 Nanyang Drive, Singapore, 637553 SingaporeSearch for more papers by this authorYun Zheng, Yun Zheng School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 SingaporeSearch for more papers by this authorKun Rui, Kun Rui Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University (NanjingTech), 2100 Nanjing, ChinaSearch for more papers by this authorHuey Hoon Hng, Huey Hoon Hng School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 SingaporeSearch for more papers by this authorKedar Hippalgaonkar, Kedar Hippalgaonkar Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Innovis #08-03, Singapore, 138634 SingaporeSearch for more papers by this authorJianwei Xu, Jianwei Xu Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Innovis #08-03, Singapore, 138634 SingaporeSearch for more papers by this authorWenping Sun, Wenping Sun Institute for Superconducting and Electronic Materials, Australian Institute for, Innovative Materials, University of Wollongong, NSW, 2522 AustraliaSearch for more papers by this authorJixin Zhu, Corresponding Author Jixin Zhu iamjxzhu@njtech.edu.cn Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University (NanjingTech), 2100 Nanjing, ChinaE-mail: iamjxzhu@njtech.edu.cn, alexyan@ntu.edu.sgSearch for more papers by this authorQingyu Yan, Corresponding Author Qingyu Yan alexyan@ntu.edu.sg School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore Energy Research Institute (ERI@N), Interdisciplinary Graduate School, Nanyang Technological University, 50 Nanyang Drive, Singapore, 637553 SingaporeE-mail: iamjxzhu@njtech.edu.cn, alexyan@ntu.edu.sgSearch for more papers by this authorWei Huang, Wei Huang Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University (NanjingTech), 2100 Nanjing, ChinaSearch for more papers by this author First published: 08 June 2017 https://doi.org/10.1002/smll.201700661Citations: 120Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Abstract Recent progress in the currently available methods of producing black phosphorus bulk and phosphorene are presented. The effective passivation approaches toward improving the air stability of phosphorene are also discussed. Furthermore, the research efforts on the phosphorene and phosphorene-based materials for potential applications in lithium ion batteries, sodium ion batteries, and thermoelectric devices are summarized and highlighted. Finally, the outlook including challenges and opportunities in these research fields are discussed. Citing Literature Volume13, Issue28July 26, 20171700661 RelatedInformation

Binary metal selenides (ZnSe/CoSe) encapsulated in N-doped carbon polyhedra interconnected with carbon nanotubes (ZCS@NC/CNTs) are prepared through a simple solution method, involving subsequent <italic>in situ</italic> pyrolysis and selenization of the metal–organic framework (MOF) precursor.

Abstract A facile pathway of the electrocatalytic nitrogen oxidation reaction (NOR) to nitrate is proposed, and Ru‐doped TiO 2 /RuO 2 (abbreviated as Ru/TiO 2 ) as a proof‐of‐concept catalyst is employed accordingly. Density functional theory (DFT) calculations suggest that Ru δ + can function as the main active center for the NOR process. Remarkably doping Ru into the TiO 2 lattice can induce an upshift of the d‐band center of the Ru site, resulting in enhanced activity for accelerating electrochemical conversion of inert N 2 to active NO*. Overdoping of Ru ions will lead to the formation of additional RuO 2 on the TiO 2 surface, which provides oxygen evolution reaction (OER) active sites for promoting the redox transformation of the NO* intermediate to nitrate. However, too much RuO 2 in the catalyst is detrimental to both the selectivity of the NOR and the Faradaic efficiency due to the dominant OER process. Experimentally, a considerable nitrate yield rate of 161.9 µmol h −1 g cat −1 (besides, a total nitrate yield of 47.9 µg during 50 h) and a highest nitrate Faradaic efficiency of 26.1% are achieved by the Ru/TiO 2 catalyst (with the hybrid composition of Ru x Ti y O 2 and extra RuO 2 by 2.79 wt% Ru addition amount) in 0.1 m Na 2 SO 4 electrolyte.

Photocatalytic CO2 reduction has been regarded as an appealing pathway for CO2 conversion to hydrocarbon fuels. To boost the CO2 photoreduction performance, developing suitable cocatalyst on the photocatalysts is an efficient strategy. Herein, Co2N is employed as novel noble-metal-free cocatalyst to promote the CO2 photoreduction performance of BiOBr ultrathin nanosheets. The optimal Co2N/BiOBr delivers a high selectivity CO formation rate of 67.8 µmol g−1 h−1 in pure water without sacrificial reagent or extra photosensitizer, roughly 6 times higher than BiOBr. Co2N can create strong electronic interactions with BiOBr, steering the electron transfer from BiOBr, across the interface to metallic Co2N and finally to the surface. Apart from the charge separation steering, the activation energy barrier can be lowered on Co2N surface via stabilize COOH* intermediates, tuning the rate-limiting step from the formation of COOH* on BiOBr to the formation of CO* on Co2N, jointly optimize the CO2 photoreduction activity. This strategy affords an accessible pathway for designing cocatalysts for efficient CO2 photoreduction.

Synthesizing urea from nitrate and carbon dioxide through an electrocatalysis approach under ambient conditions is extraordinarily sustainable. However, this approach still lacks electrocatalysts developed with high catalytic efficiencies, which is a key challenge. Here, we report the high-efficiency electrocatalytic synthesis of urea using indium oxyhydroxide with oxygen vacancy defects, which enables selective C-N coupling toward standout electrocatalytic urea synthesis activity. Analysis by operando synchrotron radiation-Fourier transform infrared spectroscopy showcases that *CO2NH2 protonation is the potential-determining step for the overall urea formation process. As such, defect engineering is employed to lower the energy barrier for the protonation of the *CO2NH2 intermediate to accelerate urea synthesis. Consequently, the defect-engineered catalyst delivers a high Faradaic efficiency of 51.0%. In conjunction with an in-depth study on the catalytic mechanism, this design strategy may facilitate the exploration of advanced catalysts for electrochemical urea synthesis and other sustainable applications.

Two dimensional (2D) bimetal–MOFs (Co<italic>x</italic>Fe–MOF) nanosheets have been successfully synthesized, which can simultaneously meet the requirement of both OER and NRR, thus providing the potential for coupling both OER and NRR in a full-cell configuration.

We investigate the structural and physical properties of the AgSnmSbSem+2 system with m = 1–20 (i.e., SnSe matrix and ∼5–50% AgSbSe2) from atomic, nano, and macro length scales. We find the 50:50 composition, with m = 1 (i.e., AgSnSbSe3), forms a stable cation-disordered cubic rock-salt p-type semiconductor with a special multi-peak electronic valence band structure. AgSnSbSe3 has an intrinsically low lattice thermal conductivity of ∼0.47 W m–1 K–1 at 673 K owing to the synergy of cation disorder, phonon anharmonicity, low phonon velocity, and low-frequency optical modes. Furthermore, Te alloying on Se sites creates a quinary high-entropy NaCl-type solid solution AgSnSbSe3-xTex with randomly disordered cations and anions. The extra point defects and lattice dislocations lead to glass-like lattice thermal conductivities of ∼0.32 W m–1 K–1 at 723 K and higher hole carrier concentration than AgSnSbSe3. Concurrently, the Te alloying promotes greater convergence of the multiple valence band maxima in AgSnSbSe1.5Te1.5, the composition with the highest configurational entropy. Facilitated by these favorable modifications, we achieve a high average power factor of ∼9.54 μW cm–1 K–2 (400–773 K), a peak thermoelectric figure of merit ZT of 1.14 at 723 K, and a high average ZT of ∼1.0 over a wide temperature range of 400–773 K in AgSnSbSe1.5Te1.5.

A 2D few-layer black phosphorus/NiCo MOF (BP/NiCo MOF) hybrid is rationally designed and directly utilized as a lithium-ion battery anode.

Thermoelectrics is attractive as a green and sustainable way for harnessing waste heat and cooling applications. Designing high performance thermoelectrics involves navigating the complex interplay between electronic and heat transports. This fundamentally involves understanding the scattering physics of both electrons and phonons, as well as maximizing symmetry-breaking in entropy and electronic transports. In the last two decades, thermoelectrics have progressed in leaps and bounds thanks to parallel advancements in scientific technologies and physical understandings. Figure of merit zT of 2 and above have been consistently reported in various materials, especially Chalcogenides. In this review, we provide a broad picture of physically driven optimization strategies for thermoelectric materials, with emphasis on electronic transport aspect of inorganic materials. We also discuss and analyzes various newly coined metrics such as quality factors, electronics quality factor, electronic fitness function, weighted mobility, and Fermi surface complexity factor. More importantly, we look at the non-trivial interdependencies between various physical parameters even at a very fundamental level. Moving forward, we discuss the outlook for the potential of 3D printing and device oriented research in thermoelectrics. The intuition derived from this review will be useful not only to guide materials selection, but also research directions in the coming years.

We introduce Sb2Si2Te6 as a high-performance thermoelectric material. Single-crystal X-ray diffraction analysis indicates that Sb2Si2Te6 has a layered two-dimensional structure with Sb3+ cations and [Si2Te6]6− units as building blocks adopting the Fe2P2Se6 structure type. Sb2Si2Te6 is a direct-band-gap semiconductor with valence-band maximum and conduction-band minimum at the Z point in the Brillouin zone, where the band is doubly degenerate. Polycrystalline bulk pellets of Sb2Si2Te6 with randomly packed grains exhibit an intrinsically high thermoelectric figure of merit ZT of ∼1.08 at 823 K. We then create a cellular nanostructure with ultrathin Si2Te3 nanosheets covering the Sb2Si2Te6 grains, which act as a hole-transmitting electron-blocking filter and at the same time cause extra phonon scattering. This dual function of the cellular nanostructure achieves an ultralow thermal conductivity value of ∼0.29 Wm−1K−1 and a high ZT value of ∼1.65 at 823 K for Sb2Si2Te6, along with a high average ZT value of ∼0.98.

Aqueous aluminum metal batteries (AMBs) are regarded as one of the most sustainable energy storage systems among post-lithium-ion candidates, which is attributable to their highest theoretical volumetric capacity, inherent safe operation, and low cost. Yet, the development of aqueous AMBs is plagued by the incapable aluminum plating in an aqueous solution and severe parasitic reactions, which results in the limited discharge voltage, thus making the development of aqueous AMBs unsuccessful so far. Here, we demonstrate that amorphization is an effective strategy to tackle these critical issues of a metallic Al anode by shifting the reduction potential for Al deposition. The amorphous aluminum (a-Al) interfacial layer is triggered by an in situ lithium-ion alloying/dealloying process on a metallic Al substrate with low strength. Unveiled by experimental and theoretical investigations, the amorphous structure greatly lowers the Al nucleation energy barrier, which forces the Al deposition competitive to the electron-stealing hydrogen evolution reaction (HER). Simultaneously, the inhibited HER mitigates the passivation, promoting interfacial ion transfer kinetics and enabling steady aluminum plating/stripping for 800 h in the symmetric cell. The resultant multiple full cells using Al@a-Al anodes deliver approximately a 0.6 V increase in the discharge voltage plateau compared to that of bare Al-based cells, which far outperform all reported aqueous AMBs. In both symmetric cells and full cells, the excellent electrochemical performances are achieved in a noncorrosive, low-cost, and fluorine-free Al2(SO4)3 electrolyte, which is ecofriendly and can be easily adapted for sustainable large-scale applications. This work brings an intriguing picture of the design of metallic anodes for reversible and high-voltage AMBs.

Abstract With the excessive consumption of nonrenewable resources, the exploration of effective and durable materials is highly sought after in the field of sustainable energy conversion and storage system. In this aspect, metal‐organic frameworks (MOFs) are a new class of crystalline porous organic‐inorganic hybrid materials. MOFs have recently been gaining traction in energy‐related fields. Owing to the coordination flexibility and multiple accessible oxidation states of vanadium ions or clusters, vanadium‐MOFs (V‐MOFs) possess unique structural characteristics and satisfactory electrochemical properties. Furthermore, V‐MOFs‐derived materials also exhibit superior electrical conductivity and stability when used as electrocatalysts and electrode materials. This review summarizes the research progress of V‐MOFs (inclusive of pristine V‐MOFs, V/M‐MOFs, and POV‐based MOFs) and their derivatives (vanadium oxides, carbon‐coated vanadium oxide, vanadium phosphate, vanadate, and other vanadium doped nanomaterials) in electrochemical energy conversion (water splitting, oxygen reduction reaction) and energy storage (supercapacitor, rechargeable battery). Future possibilities and challenges for V‐MOFs and their derivatives in terms of design and synthesis are discussed. Lastly, their applications in energy‐related fields are also highlighted.

Artificial nitrogen conversion reactions, such as the production of ammonia via dinitrogen or nitrate reduction and the synthesis of organonitrogen compounds via C-N coupling, play a pivotal role in the modern life. As alternatives to the traditional industrial processes that are energy- and carbon-emission-intensive, electrocatalytic nitrogen conversion reactions under mild conditions have attracted significant research interests. However, the electrosynthesis process still suffers from low product yield and Faradaic efficiency, which highlight the importance of developing efficient catalysts. In contrast to the transition-metal-based catalysts that have been widely studied, the p-block-element-based catalysts have recently shown promising performance because of their intriguing physiochemical properties and intrinsically poor hydrogen adsorption ability. In this Perspective, we summarize the latest breakthroughs in the development of p-block-element-based electrocatalysts toward nitrogen conversion applications, including ammonia electrosynthesis from N2 reduction and nitrate reduction and urea electrosynthesis using nitrogen-containing feedstocks and carbon dioxide. The catalyst design strategies and the underlying reaction mechanisms are discussed. Finally, major challenges and opportunities in future research directions are also proposed.

Inorganic thermoelectrics have progressed in leaps and bounds in the recent years. This is largely driven by the advancements in both physical understanding coupled with structural properties. In particular, p-type AgSbTe2 has recently emerged as one of the best thermoelectric materials for low and medium temperature applications. Nevertheless, it suffers from longstanding stability and inconsistency problems, which results in n-type Ag2Te precipitates and drastic deterioration in performance. In this work, we trace the origin of the variability of thermoelectric properties of AgSbTe2 found in literatures to the cooling rate during synthesis. Furthermore, we demonstrate a non-equilibrium annealing strategy to achieve consistent properties. Ultimately, a peak zT of 1.15 at 623 K was achieved for optimally annealed and quenched pristine AgSbTe2. Importantly, in the absence of dopant to fully stabilize the AgSbTe2 phase, we propose limiting its application to the vicinity of room temperature for cooling, and above 633 K for waste heat harvesting.

In this work, we show that the maximum thermopower of few layers graphene (FLG) films could be greatly enhanced up to ∼700 μV/K after oxygen plasma treatment. The electrical conductivities of these plasma treated FLG films remain high, for example, ∼104 S/m, which results in power factors as high as ∼4.5 × 10−3 W K−2 m−1. In comparison, the pristine FLG films show a maximum thermopower of ∼80 μV/K with an electrical conductivity of ∼5 × 104 S/m. The proposed mechanism is due to generation of local disordered carbon that opens the band gap. Measured thermopowers of single-layer graphene (SLG) films and reduced graphene oxide (rGO) films were in the range of −40 to 50 and −10 to 20 μV/K, respectively. However, such oxygen plasma treatment is not suitable for SLG and rGO films. The SLG films were easily destroyed during the treatment while the electrical conductivity of rGO films is too low.

Pd monometallic and Au–Pd bimetallic catalysts supported on surface-functionalized SBA-16 were prepared by a conventional adsorption method and were examined using X-ray diffraction, nitrogen physisorption, UV–vis spectroscopy, and high-resolution transmission microscopy. SBA-16 with the unique “super-cage” structure effectively controlled the formation of dispersed noble metal nanoparticles in the mesoporous channels. These confined nanoparticles with a narrow particle size distribution exhibited excellent catalytic activity in the solvent-free benzyl alcohol selective oxidation with molecular oxygen. Amine-functionalization remarkably improved the selectivity towards benzaldehyde. Au–Pd bimetallic catalysts showed enhanced catalytic performance compared to the Au and Pd monometallic catalysts. The highest turnover frequency of 8667 h−1 was achieved over a bimetallic catalyst with Au:Pd molar ratio of 1:5; this good catalytic activity can be maintained after five recycling runs. The characterization results of scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy revealed that the bimetallic catalyst was constructed of uniformly alloyed nanoparticles with Pd cluster-on-Au cluster structure. The synergetic effect between Au and Pd nanocluster was suggested to account for the better catalytic activity of bimetallic catalysts because the size-dependent effect can be ruled out due to the effective confinement of noble metal nanoparticles by SBA-16 mesostructure.

Deep-sea hydrothermal vent chimneys harbor a high diversity of largely unknown microorganisms. Although the phylogenetic diversity of these microorganisms has been described previously, the adaptation and metabolic potential of the microbial communities is only beginning to be revealed. A pyrosequencing approach was used to directly obtain sequences from a fosmid library constructed from a black smoker chimney 4143-1 in the Mothra hydrothermal vent field at the Juan de Fuca Ridge. A total of 308,034 reads with an average sequence length of 227 bp were generated. Comparative genomic analyses of metagenomes from a variety of environments by two-way clustering of samples and functional gene categories demonstrated that the 4143-1 metagenome clustered most closely with that from a carbonate chimney from Lost City. Both are highly enriched in genes for mismatch repair and homologous recombination, suggesting that the microbial communities have evolved extensive DNA repair systems to cope with the extreme conditions that have potential deleterious effects on the genomes. As previously reported for the Lost City microbiome, the metagenome of chimney 4143-1 exhibited a high proportion of transposases, implying that horizontal gene transfer may be a common occurrence in the deep-sea vent chimney biosphere. In addition, genes for chemotaxis and flagellar assembly were highly enriched in the chimney metagenomes, reflecting the adaptation of the organisms to the highly dynamic conditions present within the chimney walls. Reconstruction of the metabolic pathways revealed that the microbial community in the wall of chimney 4143-1 was mainly fueled by sulfur oxidation, putatively coupled to nitrate reduction to perform inorganic carbon fixation through the Calvin-Benson-Bassham cycle. On the basis of the genomic organization of the key genes of the carbon fixation and sulfur oxidation pathways contained in the large genomic fragments, both obligate and facultative autotrophs appear to be present and contribute to biomass production.

Low cost sulfonated poly (ether ether ketone) membranes have been successfully prepared and optimized at various sulfonation conditions by casting method for vanadium redox battery applications. The optimized SPEEK membrane was initially tested in the G1 vanadium redox battery (VRB) before being evaluated in the G2 vanadium bromide redox flow battery (V/Br), and the performance was compared to that of Nafion 117. From the G1 VRB performance tests, the energy efficiency of the membrane was found to be 77%, slightly higher than Nafion 117 which gave 73% at current density 40 mA cm−2. For the first time, the SPEEK membrane was evaluated in the G2 V/Br at two different ratios of bromine complexing agents and the performance was assessed from the measured cell efficiencies. At 4 mA cm−2, the optimum energy efficiency was 76% using SPEEK in the presence of 0.19 M MEM and 0.56 M MEP, when compared to 75% obtained with Nafion 117. Similar to Nafion 117, SPEEK also exhibits excellent chemical stability in the highly oxidizing electrolytes. The SPEEK membrane thus appears to be a promising candidate for both G1 and G2 VRB applications.

Reduced graphene oxide (rGO) supported highly porous polycrystalline V2O5 spheres (V2O5/rGO) were prepared by using a solvothermal approach followed by an annealing process. Initially, reduced vanadium oxide (rVO) nanoparticles with sizes in the range of 10–50 nm were formed through heterogeneous nucleation on rGO sheets during the solvothermal process. These rVO nanoparticles were oxidized to V2O5 after the annealing process in air at 350 °C and assembled into polycrystalline porous spheres with sizes of 200–800 nm. The weight ratio between the rGO and V2O5 is tunable by changing the weight ratio of the precursors, which in turn affects the morphology of V2O5/rGO composites. The V2O5/rGO composites display superior cathode performances with highly reversible specific capacities, good cycling stabilities and excellent rate capabilities (e.g. 102 mA h g−1 at 19 C).

1D hierarchical tubular MnO2 nanostructures have been prepared through a facile hydrothermal method using carbon nanofibres (CNFs) as sacrificial template. The morphology of MnO2 nanostructures can be adjusted by changing the reaction time or annealing process. Polycrystalline MnO2 nanotubes are formed with a short reaction time (e.g., 10 min) while hierarchical tubular MnO2 nanostructures composed of assembled nanosheets are obtained at longer reaction times (>45 min). The polycrystalline MnO2 nanotubes can be further converted to porous nanobelts and sponge-like nanowires by annealing in air. Among all the types of MnO2 nanostructures prepared, tubular MnO2 nanostructures composed of assembled nanosheets show optimized charge storage performance when tested as supercapacitor electrodes, for example, delivering an power density of 13.33 kW·kg–1 and a energy density of 21.1 Wh·kg–1 with a long cycling life over 3000 cycles, which is mainly related to their features of large specific surface area and optimized charge transfer pathway.

The electronically conductive networks in the MnO-based anode of lithium ion batteries have been optimized by employing different carbonaceous materials as building blocks.

We report the synthesis of two-dimensional (2D) NiCo2O4 nanosheet-coated three-dimensional graphene network (3DGN), which is then used as an electrode for high-rate, long-cycle-life supercapacitors. Using the 3DGN and nanoporous nanosheets, an ultrahigh specific capacitance (2173 F g−1 at 6 A g−1), excellent rate capability (954 F g−1 at 200 A g−1) and superior long-term cycling performance (94% capacitance retention after 14 000 cycles at 100 A g−1) are achieved.

A general and simple approach for large-scale synthesis of porous hollow spinel AFe2O4 nanoarchitectures via metal organic framework self-sacrificial template strategy is proposed. By employing this method, we can successfully synthesize uniform NiFe2O4, ZnFe2O4, and CoFe2O4 hollow architectures that are hierarchically assembled by nanoparticles. When these hollow microcubes were tested as anode for lithium ion batteries, good rate capability and long-term cycling stability can be achieved. For example, high specific capacities of 636, 449, and 380 mA h g(-1) were depicted by NiFe2O4, ZnFe2O4, and CoFe2O4, respectively, at a high current density of 8.0 A g(-1). NiFe2O4 exhibits high specific capacities of 841 and 447 mA h g(-1) during the 100th cycle when it was tested at current densities of 1.0 and 5.0 A g(-1), respectively. Discharge capacities of 390 and 290 mA h g(-1) were delivered by the ZnFe2O4 and CoFe2O4, respectively, during the 100th cycle at 5.0 A g(-1).

Ag is deposited on the surface of Au nanoparticles functionalized with 4-mercaptobenzoic acid (MBA). Exceptionally strong surface-enhanced Raman scattering (SERS) signals are observed from the resulting colloid. Using SERS as a tool, evidence is obtained for the embedding of MBA inside the nanoscale metal layer. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Materials with ordered mesoporous structures have shown great potential in a wide range of applications. In particular, the combination of mesoporosity, low dimensionality, and well-defined morphology in nanostructures may exhibit even more attractive features. However, the synthesis of such structures is still challenging in polar solvents. Herein, we report the preparation of ultrathin two-dimensional (2D) nanoflakes of transition-metal phosphates, including FePO4, Mn3(PO4)2, and Co3(PO4)2, with highly ordered mesoporous structures in a nonpolar solvent. The as-obtained nanoflakes with thicknesses of about 3.7 nm are constructed from a single layer of parallel-packed pore channels. These uniquely ordered mesoporous 2D nanostructures may originate from the 2D assembly of cylindrical micelles formed by the amphiphilic precursors in the nonpolar solvent. The 2D mesoporous FePO4 nanoflakes were used as the cathode for a lithium-ion battery, which exhibits excellent stability and high rate capabilities.

A stable aqueous dispersion of hydrophobic single-walled carbon nanotubes (SWCNTs) and amphiphilic graphene oxide (GO) nano-sheets was produced by sonication mixing without assistance of any surfactant. Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and electrical characterization suggest that SWCNTs are completely wrapped by GO nano-sheets. The spontaneous formation of such a core–shell structure is due to the strong pi–pi stacking interaction between the two materials. The electronic coupling between them is evidenced by time-resolved fluorescence measurement. The potential of such a nanocarbon hybrid in optical limiting and supercapacitor applications is discussed.

Additive manufacturing such as selective laser sintering (SLS) offers the strategies to create 3D complex components with desirable mechanical, electrical and thermal properties using the composite powders as feeding materials. This work proposes a new fabrication approach to preparing carbon nanotube (CNT) composite powders and utilizes them for SLS process. As compared with the hot-compression process, the SLS process could offer an effective method to fabricate the CNT/Polymer composite with electrically conductive segregated structures. At a small loading range of CNTs (<1 wt%), the laser-sintered composites exhibit significant improvements in the electrical conductivity up to anti-static and conductive range qualifying the applications in automobile and aerospace. However, the enhancement in thermal conductivity of laser-sintered composites is not comparable with that of hot-compressed ones. The process-structure-property relationships are further investigated to study the different processes induced microstructures and the underlying mechanism of thermal and electrical performances.

Exploring earth-abundant electrocatalysts to realize efficient oxygen evolution reaction (OER) is highly desired for developing sustainable electrochemical energy storage and conversion technologies. Herein, ultrathin single-crystalline Fe-doped nickel thiophosphate (NiPS3) nanosheets prepared in large scale by an easy solid-state method were demonstrated to be highly efficient OER electrocatalysts. The density functional theory (DFT) calculations reveal that the Fe-doping effectively decreases the energy barrier of OER path by reducing the binding of the oxygen-containing species on the surface of NiPS3. As such, the Fe-doped NiPS3 nanosheets show a low overpotential of 256 mV to reach a current density of 30 mA cm−2 and a small Tafel slope of 46 mV dec−1. To our knowledge, this is one of the best OER electrocatalysts in alkaline medium to date. The in-depth mechanism study demonstrates that the in-situ formed Fe-doped nickel oxides/hydroxides shell, resulting from the surface oxidation during the OER process, not only may serve as favorable electrocatalytic species but also improves the chemical stability of the Fe-doped NiPS3 in alkaline electrolyte. This work provides a new perspective for designing highly efficient OER electrocatalysts based on the ternary two-dimensional layered metal thiophosphates.

Abstract Vertebrates diverged from other chordates ~500 Myr ago and experienced successful innovations and adaptations, but the genomic basis underlying vertebrate origins are not fully understood. Here we suggest, through comparison with multiple lancelet (amphioxus) genomes, that ancient vertebrates experienced high rates of protein evolution, genome rearrangement and domain shuffling and that these rates greatly slowed down after the divergence of jawed and jawless vertebrates. Compared with lancelets, modern vertebrates retain, at least relatively, less protein diversity, fewer nucleotide polymorphisms, domain combinations and conserved non-coding elements (CNE). Modern vertebrates also lost substantial transposable element (TE) diversity, whereas lancelets preserve high TE diversity that includes even the long-sought RAG transposon. Lancelets also exhibit rapid gene turnover, pervasive transcription, fastest exon shuffling in metazoans and substantial TE methylation not observed in other invertebrates. These new lancelet genome sequences provide new insights into the chordate ancestral state and the vertebrate evolution.

We demonstrate a facile colloidal method for synthesizing Janus nanoparticles, whose eccentric polymer shells are exploited to fabricate eccentric bimetallic cores.

Abstract The development of 2‐dimensional materials has expanded beyond the realm of graphene, and now includes inorganic 2‐dimensional transition metal oxides/hydroxides, which show promise for a wide range of applications. As an emerging class of nanoscale materials, they show unprecedented properties that are unattainable in their bulk lamellar systems, which can be attributed to their confined thickness compared to several tens of micrometer lateral dimensions. Such qualities make them viable candidates for battery and supercapacitor applications. There are a few challenges ahead for 2‐dimensional transition metal oxides/hydroxides, including the limited types of 2‐dimensional parent materials in bulk form, the controlled synthesis of 2‐dimensional nanostructures with nonlayered structures, and the ability to control the properties of layers by tuning the chemistry and nanoscopic features. This Focus Review will cover the research landscape of 2‐dimensional transition metal oxides/hydroxides, ranging from synthetic approaches, to understanding the properties that emerge at the single‐layer scale, to exploiting these properties in both new and existing technologies.

The off-centered Ge leads to the ultralow lattice thermal conductivity and record high average <italic>ZT</italic> for n-type PbSe.

Here we present a novel combined-strategy of cation tuning and surface engineering for the fabrication of highly active, earth-abundant, and robust two-dimensional Ni2P electrocatalyst. The nanosheets have lateral sizes of few hundred nm with thicknesses of ~6 nm. Our theoretical calculations suggest the effectiveness of vanadium doping and oxygen plasma, which do not only enhance the density-of-state at Fermi level, but also make the Ni sites more susceptible to OH− adsorption. The oxygen plasma treatment can increase the wettability of the catalyst toward KOH solution, improving the contact angle from 44.95° to 16.8°, and also induce a higher BET surface area; hence, more active sites and lower charge transfer resistance are obtained. As a result, the catalyst requires small overpotentials of 257 and 108 mV to drive ±10 mA cm−2 alongside with modest Tafel slope of 43.5 and 72.3 mV dec−1 for oxygen evolution reaction and hydrogen evolution reaction in 1.0 M KOH solution, respectively. When employed for overall water splitting, the catalyst demonstrates a low voltage of 1.56 V to achieve 10 mA cm−2 with good stability and durability, outperforming the state-of-the-art IrO2 || Pt/C which needs 1.69 V. This work opens a new approach to engineer low-cost monometallic phosphides for highly efficient water splitting.

Outstanding sodium and lithium storage capability is successfully demonstrated in ultrathin NiO nanosheets (4–5 nm in thickness) synthesized via a facile solvothermal process followed by annealing in air. For sodium storage, the NiO nanosheets deliver a high reversible specific capacity of 299 mA h g−1 at a current density of 1 A g−1, and the capacity still remains up to 154 mA h g−1 at 10 A g−1. Upon charge/discharge cycling, the specific capacity maintains to be as high as 266 mA h g−1 during the 100th cycle at 1 A g−1. Such sodium storage capability of NiO nanosheets is by far one of the best reported for transition metal oxides. For lithium storage, the cell achieves a high reversible specific capacity of 1242 and 250 mA h g−1 at 0.2 and 15 A g−1, respectively. The capacity for lithium storage maintains to be 851 mA h g−1 during the 170th cycle at 2 A g−1. The present results demonstrate that ultrathin NiO nanosheets are highly attractive for fast sodium/lithium diffusion with high-rate capability for rechargeable sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs).

A unique controlled synthesis of zinc cobalt sulfide nanostructures is obtained by a facile oil phase approach.

One-dimensional CuS/electrospun carbon nanofiber heteroarchitectures (CuS/EC) with high catalytic activity have been successfully fabricated by combining the versatility of the electrospinning technique and following a hydrothermal process. The CuS nanoparticles as the secondary nanostructures were uniformly grown on the primary electrospun carbon nanofibers with good dispersion by optimizing reaction conditions. It was found that the l-cysteine used as the sulfur donor and chelating reagent was favored for the growth of CuS on the carbon fibers. A possible formation mechanism and growth process of the CuS nanoparticles on the carbon fibers is discussed based on the experimental results. The as-prepared CuS/EC composite was then spray-deposited on FTO glass and demonstrated good performance in quantum dot-sensitized solar cells (QDSCs), which was higher than the conventional Pt electrode. The good performance is attributed to its heteroarchitecture. The CuS nanoparticles with high catalytic activity play the main role in the reduction process of the oxidized polysulfide, while the carbon nanofibers with the 3-D mat morphology bridge all the CuS nanoparticles as the framework and facilitate the charge transport during the catalysis process.

Metal vanadium phosphates (MVP), particularly Li3V2(PO4)3 (LVP) and Na3V2(PO4)3 (NVP), are regarded as the next-generation cathode materials in lithium/sodium ion batteries. These materials possess desirable properties such as high stability, theoretical capacity, and operating voltages. Yet, low electrical/ionic conductivities of LVP and NVP have limited their applications in demanding devices such as electric vehicles. In this work, a novel synthesis route for the preparation of LVP/NVP micro/mesoporous 3D foams via assembly of elastin-like polypeptides is demonstrated. The as-synthesized MVP 3D foams consist of microporous networks of mesoporous nanofibers, where the surfaces of individual fibers are covered with MVP nanocrystallites. TEM images further reveal that LVP/NVP nanoparticles are about 100-200 nm in diameter, with each particle enveloped by a 5 nm thick carbon shell. The MVP 3D foams prepared in this work exhibit ultrafast rate capabilities (79 mA h g(-1) at 100C and 66 mA h g(-1) at 200C for LVP 3D foams; 73 mA h g(-1) at 100C and 51 mA h g(-1) at 200C for NVP 3D foams) and excellent cycle performance (almost 100% performance retention after 1000 cycles at 100C); their properties are far superior compared to current state-of-the-art active materials.