Zheng Jiang

<h2>Summary</h2> Nitrogen fixation under ambient conditions remains a significant challenge. Here, we report nitrogen fixation by Ru single-atom electrocatalytic reduction at room temperature and pressure. In contrast to Ru nanoparticles, single Ru sites supported on N-doped porous carbon greatly promoted electroreduction of aqueous N₂ selectively to NH₃, affording an NH₃ formation rate of 3.665 <mml:math><mml:mrow><mml:mi>m</mml:mi><mml:mi>g</mml:mi><mml:mrow><mml:mi>N</mml:mi><mml:mi>H</mml:mi><mml:mi>3</mml:mi></mml:mrow><mml:msup><mml:mi>h</mml:mi><mml:mrow><mml:mo>−</mml:mo><mml:mi>1</mml:mi></mml:mrow></mml:msup><mml:mi>m</mml:mi><mml:mi>g</mml:mi><mml:mrow><mml:mi>Ru</mml:mi></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mi>1</mml:mi></mml:mrow></mml:mrow></mml:math> at −0.21 V versus the reversible hydrogen electrode. Importantly, the addition of ZrO₂ was found to significantly suppress the competitive hydrogen evolution reaction. An NH₃ faradic efficiency of about 21% was achieved at a low overpotential (0.17 V), surpassing many other reported catalysts. Experiments combined with density functional theory calculations showed that the Ru sites with oxygen vacancies were major active centers that permitted stabilization of *NNH, destabilization of *H, and enhanced N₂ adsorption. We envision that optimization of ZrO₂ loading could further facilitate electroreduction of N₂ at both high NH₃ synthesis rate and faradic efficiency.

It is of great importance to understand the origin of high oxygen-evolving activity of state-of-the-art multimetal oxides/(oxy)hydroxides at atomic level. Herein we report an evident improvement of oxygen evolution reaction activity via incorporating iron and vanadium into nickel hydroxide lattices. X-ray photoelectron/absorption spectroscopies reveal the synergistic interaction between iron/vanadium dopants and nickel in the host matrix, which subtly modulates local coordination environments and electronic structures of the iron/vanadium/nickel cations. Further, in-situ X-ray absorption spectroscopic analyses manifest contraction of metal-oxygen bond lengths in the activated catalyst, with a short vanadium-oxygen bond distance. Density functional theory calculations indicate that the vanadium site of the iron/vanadium co-doped nickel (oxy)hydroxide gives near-optimal binding energies of oxygen evolution reaction intermediates and has lower overpotential compared with nickel and iron sites. These findings suggest that the doped vanadium with distorted geometric and disturbed electronic structures makes crucial contribution to high activity of the trimetallic catalyst.

For the large-scale sustainable implementation of polymer electrolyte membrane fuel cells in vehicles, high-performance electrocatalysts with low platinum consumption are desirable for use as cathode material during the oxygen reduction reaction in fuel cells. Here we report a carbon black-supported cost-effective, efficient and durable platinum single-atom electrocatalyst with carbon monoxide/methanol tolerance for the cathodic oxygen reduction reaction. The acidic single-cell with such a catalyst as cathode delivers high performance, with power density up to 680 mW cm-2 at 80 °C with a low platinum loading of 0.09 mgPt cm-2, corresponding to a platinum utilization of 0.13 gPt kW-1 in the fuel cell. Good fuel cell durability is also observed. Theoretical calculations reveal that the main effective sites on such platinum single-atom electrocatalysts are single-pyridinic-nitrogen-atom-anchored single-platinum-atom centres, which are tolerant to carbon monoxide/methanol, but highly active for the oxygen reduction reaction.

A competitive complexation strategy has been developed to construct a novel electrocatalyst with Zn-Co atomic pairs coordinated on N doped carbon support (Zn/CoN-C). Such architecture offers enhanced binding ability of O2 , significantly elongates the O-O length (from 1.23 Å to 1.42 Å), and thus facilitates the cleavage of O-O bond, showing a theoretical overpotential of 0.335 V during ORR process. As a result, the Zn/CoN-C catalyst exhibits outstanding ORR performance in both alkaline and acid conditions with a half-wave potential of 0.861 and 0.796 V respectively. The in situ XANES analysis suggests Co as the active center during the ORR. The assembled zinc-air battery with Zn/CoN-C as cathode catalyst presents a maximum power density of 230 mW cm-2 along with excellent operation durability. The excellent catalytic activity in acid is also verified by H2 /O2 fuel cell tests (peak power density of 705 mW cm-2 ).

Abstract Lacking strategies to simultaneously address the intrinsic activity, site density, electrical transport, and stability problems of chalcogels is restricting their application in catalytic hydrogen production. Herein, we resolve these challenges concurrently through chemically activating the molybdenum disulfide (MoS 2 ) surface basal plane by doping with a low content of atomic palladium using a spontaneous interfacial redox technique. Palladium substitution occurs at the molybdenum site, simultaneously introducing sulfur vacancy and converting the 2H into the stabilized 1T structure. Theoretical calculations demonstrate the sulfur atoms next to the palladium sites exhibit low hydrogen adsorption energy at –0.02 eV. The final MoS 2 doped with only 1wt% of palladium demonstrates exchange current density of 805 μA cm −2 and 78 mV overpotential at 10 mA cm −2 , accompanied by a good stability. The combined advantages of our surface activating technique open the possibility of manipulating the catalytic performance of MoS 2 to rival platinum.

Electrocatalytic reduction of CO2 to fuels and chemicals is one of the most attractive routes for CO2 utilization. Current catalysts suffer from low faradaic efficiency of a CO2-reduction product at high current density (or reaction rate). Here, we report that a sulfur-doped indium catalyst exhibits high faradaic efficiency of formate (>85%) in a broad range of current density (25-100 mA cm-2) for electrocatalytic CO2 reduction in aqueous media. The formation rate of formate reaches 1449 μmol h-1 cm-2 with 93% faradaic efficiency, the highest value reported to date. Our studies suggest that sulfur accelerates CO2 reduction by a unique mechanism. Sulfur enhances the activation of water, forming hydrogen species that can readily react with CO2 to produce formate. The promoting effect of chalcogen modifiers can be extended to other metal catalysts. This work offers a simple and useful strategy for designing both active and selective electrocatalysts for CO2 reduction.

Great enthusiasm in single-atom catalysts (SACs) for the oxygen reduction reaction (ORR) has been aroused by the discovery of M–NX as a promising ORR catalysis center. However, the performance of SACs lags far behind that of state-of-the-art Pt due to the unsatisfactory adsorption–desorption behaviors of the reported catalytic centers. To address this issue, rational manipulation of the active site configuration toward a well-managed energy level and geometric structure is urgently desired, yet still remains a challenge. Herein, we report a novel strategy to accomplish this task through the construction of an Fe–Co dual-atom centered site. A spontaneously absorbed electron-withdrawing OH ligand was proposed to act proactively as an energy level modifier to empower easy intermediate desorption, while the triangular Fe–Co–OH coordination facilitates O–O bond scission. Benefiting from these attributes, the as-constructed FeCoN5–OH site enables an ORR onset potential and half-wave potential of up to 1.02 and 0.86 V (vs RHE), respectively, with an intrinsic activity over 20 times higher than the single-atom FeN4 site. Our finding not only opens up a novel strategy to tailor the electronic structure of an atomic site toward boosted activity but also provides new insights into the fundamental understanding of diatomic sites for ORR electrocatalysis.

Developing highly efficient, low-cost oxygen reduction catalysts, especially in acidic medium, is of significance toward fuel cell commercialization. Although pyrolyzed Fe-N-C catalysts have been regarded as alternatives to platinum-based catalytic materials, further improvement requires precise control of the Fe-Nx structure at the molecular level and a comprehensive understanding of catalytic site structure and the ORR mechanism on these materials. In this report, we present a microporous metal–organic-framework-confined strategy toward the preferable formation of single-atom dispersed catalysts. The onset potential for Fe-N-C is 0.92 V, comparable to that of Pt/C and outperforming most noble-metal-free catalysts ever reported. A high-spin Fe3+-N4 configuration is revealed by the 57Fe Mössbauer spectrum and X-ray absorption spectroscopy for Fe L-edge, which will convert to Fe2+-N4 at low potential. The in situ reduced Fe2+-N4 moiety from high-spin Ox-Fe3+-N4 contributes to most of the ORR activity due to its high turnover frequency (TOF) of ca. 1.71 e s–1 sites–1.

Abstract Achieving active and stable oxygen evolution reaction (OER) in acid media based on single-atom catalysts is highly promising for cost-effective and sustainable energy supply in proton electrolyte membrane electrolyzers. Here, we report an atomically dispersed Ru 1 -N 4 site anchored on nitrogen-carbon support (Ru-N-C) as an efficient and durable electrocatalyst for acidic OER. The single-atom Ru-N-C catalyst delivers an exceptionally intrinsic activity, reaching a mass activity as high as 3571 A g metal −1 and turnover frequency of 3348 O 2 h −1 with a low overpotential of 267 mV at a current density of 10 mA cm −2 . The catalyst shows no evident deactivation or decomposition after 30-hour operation in acidic environment. Operando synchrotron radiation X-ray absorption spectroscopy and infrared spectroscopy identify the dynamic adsorption of single oxygen atom on Ru site under working potentials, and theoretical calculations demonstrate that the O-Ru 1 -N 4 site is responsible for the high OER activity and stability.

The cathodic oxygen reduction reaction (ORR) is essential in the electrochemical energy conversion of fuel cells. Here, through the NH3 atmosphere annealing of a graphene oxide (GO) precursor containing trace amounts of Ru, we have synthesized atomically dispersed Ru on nitrogen-doped graphene that performs as an electrocatalyst for the ORR in acidic medium. The Ru/nitrogen-doped GO catalyst exhibits excellent four-electron ORR activity, offering onset and half-wave potentials of 0.89 and 0.75 V, respectively, vs a reversible hydrogen electrode (RHE) in 0.1 M HClO4, together with better durability and tolerance toward methanol and carbon monoxide poisoning than seen in commercial Pt/C catalysts. X-ray adsorption fine structure analysis and aberration-corrected high-angle annular dark-field scanning transmission electron microscopy are performed and indicate that the chemical structure of Ru is predominantly composed of isolated Ru atoms coordinated with nitrogen atoms on the graphene substrate. Furthermore, a density function theory study of the ORR mechanism suggests that a Ru-oxo-N4 structure appears to be responsible for the ORR catalytic activity in the acidic medium. These findings provide a route for the design of efficient ORR single-atom catalysts.

The development of active, acid-stable and low-cost electrocatalysts for oxygen evolution reaction is urgent and challenging. Herein we report an Iridium-free and low ruthenium-content oxide material (Cr0.6Ru0.4O2) derived from metal-organic framework with remarkable oxygen evolution reaction performance in acidic condition. It shows a record low overpotential of 178 mV at 10 mA cm-2 and maintains the excellent performance throughout the 10 h chronopotentiometry test at a constant current of 10 mA cm-2 in 0.5 M H2SO4 solution. Density functional theory calculations further revealed the intrinsic mechanism for the exceptional oxygen evolution reaction performance, highlighting the influence of chromium promoter on the enhancement in both activity and stability.

Development of an efficient hydrogen evolution reaction (HER) catalyst composed of earth-abundant elements is scientifically and technologically important for the water splitting associated with the conversion and storage of renewable energy. Herein we report a new class of Co–C–N complex bonded carbon (only 0.22 at% Co) for HER with a self-supported and three-dimensional porous structure that shows an unexpected catalytic activity with low overpotential (212 mV at 100 mA cm–2) and long-term stability, better than that of most traditional-metal catalysts. Experimental observations in combination with density functional theory calculations reveal that C and N hybrid coordination optimizes the charge distribution and enhances the electron transfer, which synergistically promotes the proton adsorption and reduction kinetics.

Abstract The electrochemical reduction reaction of carbon dioxide (CO2RR) to carbon monoxide (CO) is the basis for the further synthesis of more complex carbon‐based fuels or attractive feedstock. Single‐atom catalysts have unique electronic and geometric structures with respect to their bulk counterparts, thus exhibiting unexpected catalytic activities. A nitrogen‐anchored Zn single‐atom catalyst is presented for CO formation from CO2RR with high catalytic activity (onset overpotential down to 24 mV), high selectivity (Faradaic efficiency for CO (FE CO ) up to 95 % at −0.43 V), remarkable durability (&gt;75 h without decay of FE CO ), and large turnover frequency (TOF, up to 9969 h −1 ). Further experimental and DFT results indicate that the four‐nitrogen‐anchored Zn single atom (Zn‐N 4 ) is the main active site for CO2RR with low free energy barrier for the formation of *COOH as the rate‐limiting step.

Herein, a novel binuclear active site structure, Co2NxCy, is intentionally designed and successfully fabricated to efficiently catalyze the oxygen reduction reaction (ORR), which is achieved by precisely controlling the atomic scale structure of bimetal-organic frameworks before pyrolysis. Through discovering a two-atom site with Co-Co distance at 2.1–2.2 Å from aberration-corrected scanning transmission electron microscopy (STEM), as well as a novel shortened Co-Co path (2.12 Å) from the X-ray absorption spectroscopy, we for the first time identified the binuclear Co2NX site in the pyrolyzed catalyst. Combined with density functional theory (DFT) calculation, the structure is further confirmed as Co2N5. Excitingly, the Co2N5 site performs approximately 12 times higher activity than the conventional CoN4 site and the corresponding catalyst shows unprecedented catalytic activity in acidic electrolyte with half-wave potential of 0.79 V, approaching the commercial Pt/C catalyst and presenting the best one among the Co-N-C catalysts. Theoretical density functional theory calculations reveal that the novel binuclear site exhibits considerably reduced thermodynamic barrier towards ORR, thus contributing to the much higher intrinsic activity. Our finding opens up a new path to design efficient M-Nx/C catalysts, thus pushing the fuel cell industry field one step ahead.

Single-atom catalysts (SACs) are attracting widespread interest for the catalytic oxygen reduction reaction (ORR), with Fe-Nx SACs exhibiting the most promising activity. However, Fe-based catalysts suffer serious stability issues as a result of oxidative corrosion through the Fenton reaction. Herein, using a metal-organic framework as an anchoring matrix, we for the first time obtained pyrolyzed Cr/N/C SACs for the ORR, where the atomically dispersed Cr is confirmed to have a Cr-N4 coordination structure. The Cr/N/C catalyst exhibits excellent ORR activity with an optimal half-wave potential of 0.773 V versus RHE. More excitingly, the Fenton reaction is substantially reduced and, thus, the final catalysts show superb stability. The innovative and robust active site for the ORR opens a new possibility to circumvent the stability issue of the non-noble metal ORR catalysts.

Identifying effective means to improve the electrochemical performance of oxygen-evolution catalysts represents a significant challenge in several emerging renewable energy technologies. Herein, we consider metal-nitrogen-carbon sheets which are commonly used for catalyzing the oxygen-reduction reaction (ORR), as the support to load NiO nanoparticles for the oxygen-evolution reaction (OER). FeNC sheets, as the advanced supports, synergistically promote the NiO nanocatalysts to exhibit superior performance in alkaline media, which is confirmed by experimental observations and density functional theory (DFT) calculations. Our findings show the advantages in considering the support effect for designing highly active, durable, and cost-effective OER electrocatalysts.

The authors report first a new type of nitrogen‐triggered Zn single atom catalyst, demonstrating high catalytic activity and remarkable durability for the oxygen reduction reaction process. Both X‐ray absorption fine structure spectra and theoretical calculations suggest that the atomically dispersed Zn‐N 4 site is the main, as well as the most active, component with O adsorption as the rate‐limiting step at a low overpotential of 1.70 V. This work opens a new field for the exploration of high‐performance Pt‐free electrochemical oxygen reduction catalysts for fuel cells.

The water–gas shift (WGS) reaction is an industrially important source of pure hydrogen (H2) at the expense of carbon monoxide and water1,2. This reaction is of interest for fuel-cell applications, but requires WGS catalysts that are durable and highly active at low temperatures3. Here we demonstrate that the structure (Pt1–Ptn)/α-MoC, where isolated platinum atoms (Pt1) and subnanometre platinum clusters (Ptn) are stabilized on α-molybdenum carbide (α-MoC), catalyses the WGS reaction even at 313 kelvin, with a hydrogen-production pathway involving direct carbon monoxide dissociation identified. We find that it is critical to crowd the α-MoC surface with Pt1 and Ptn species, which prevents oxidation of the support that would cause catalyst deactivation, as seen with gold/α-MoC (ref. 4), and gives our system high stability and a high metal-normalized turnover number of 4,300,000 moles of hydrogen per mole of platinum. We anticipate that the strategy demonstrated here will be pivotal for the design of highly active and stable catalysts for effective activation of important molecules such as water and carbon monoxide for energy production. A stable, low-temperature water–gas shift catalyst is achieved by crowding platinum atoms and clusters on α-molybdenum carbide; the crowding protects the support from oxidation that would cause catalyst deactivation.

Abstract The development of high‐efficiency electrocatalysts for large‐scale water splitting is critical but also challenging. In this study, a hierarchical CoMoS x chalcogel was synthesized on a nickel foam (NF) through an in situ metathesis reaction and demonstrated excellent activity and stability in the electrocatalytic hydrogen evolution reaction and oxygen evolution reaction in alkaline media. The high catalytic activity could be ascribed to the abundant active sites/defects in the amorphous framework and promotion of activity through cobalt doping. Furthermore, the superhydrophilicity and superaerophobicity of micro‐/nanostructured CoMoS x /NF promoted mass transfer by facilitating access of electrolytes and ensuring fast release of gas bubbles. By employing CoMoS x /NF as bifunctional electrocatalysts, the overall water splitting device delivered a current density of 500 mA cm −2 at a low voltage of 1.89 V and maintained its activity without decay for 100 h.

Abstract Photocatalysis has been regarded as a promising strategy for hydrogen production and high-value-added chemicals synthesis, in which the activity of photocatalyst depends significantly on their electronic structures, however the effect of electron spin polarization has been rarely considered. Here we report a controllable method to manipulate its electron spin polarization by tuning the concentration of Ti vacancies. The characterizations confirm the emergence of spatial spin polarization among Ti-defected TiO 2 , which promotes the efficiency of charge separation and surface reaction via the parallel alignment of electron spin orientation. Specifically, Ti 0.936 O 2 , possessing intensive spin polarization, performs 20-fold increased photocatalytic hydrogen evolution and 8-fold increased phenol photodegradation rates, compared with stoichiometric TiO 2 . Notably, we further observed the positive effect of external magnetic fields on photocatalytic activity of spin-polarized TiO 2 , attributed to the enhanced electron-spin parallel alignment. This work may create the opportunity for tailoring the spin-dependent electronic structures in metal oxides.

Various well-defined Ni−Pt(111) model catalysts are constructed at atomic-level precision under ultra-high-vacuum conditions and characterized by X-ray photoelectron spectroscopy and scanning tunneling microscopy. Subsequent studies of CO oxidation over the surfaces show that a sandwich surface (NiO1−x/Pt/Ni/Pt(111)) consisting of both surface Ni oxide nanoislands and subsurface Ni atoms at a Pt(111) surface presents the highest reactivity. A similar sandwich structure has been obtained in supported Pt−Ni nanoparticles via activation in H2 at an intermediate temperature and established by techniques including acid leaching, inductively coupled plasma, and X-ray adsorption near-edge structure. Among the supported Pt−Ni catalysts studied, the sandwich bimetallic catalysts demonstrate the highest activity to CO oxidation, where 100% CO conversion occurs near room temperature. Both surface science studies of model catalysts and catalytic reaction experiments on supported catalysts illustrate the synergetic effect of the surface and subsurface Ni species on the CO oxidation, in which the surface Ni oxide nanoislands activate O2, producing atomic O species, while the subsurface Ni atoms further enhance the elementary reaction of CO oxidation with O.

Abstract Maximizing the platinum utilization in electrocatalysts toward oxygen reduction reaction (ORR) is very desirable for large‐scale sustainable application of Pt in energy systems. A cost‐effective carbon‐supported carbon‐defect‐anchored platinum single‐atom electrocatalysts (Pt 1 /C) with remarkable ORR performance is reported. An acidic H 2 /O 2 single cell with Pt 1 /C as cathode delivers a maximum power density of 520 mW cm −2 at 80 °C, corresponding to a superhigh platinum utilization of 0.09 g Pt kW −1 . Further physical characterization and density functional theory computations reveal that single Pt atoms anchored stably by four carbon atoms in carbon divacancies (Pt‐C 4 ) are the main active centers for the observed high ORR performance.

Abstract Exploring of new catalyst activation principle holds a key to unlock catalytic powers of cheap and earth‐abundant materials for large‐scale applications. In this regard, the vacancy defects have been proven to be effective to initiate catalytic active sites and endow high electrocatalytic activities. However, such electrocatalytically active defects reported to date have been mostly formed by anion vacancies. Herein, it is demonstrated for the first time that iron cation vacancies induce superb water splitting bifunctionality in alkaline media. A simple wet‐chemistry method is developed to grow ultrathin feroxyhyte (δ‐FeOOH) nanosheets with rich Fe vacancies on Ni foam substrate. The theoretical and experimental results confirm that, in contrast to anion vacancies, the formation of rich second neighboring Fe to Fe vacancies in δ‐FeOOH nanosheets can create catalytic active centers for both hydrogen and oxygen evolution reactions. The atomic level insight into the new catalyst activation principle based on metal vacancies is adaptable for developing other transition metal electrocatalysts, including Fe‐based ones.

Abstract The electrochemical N 2 fixation, which is far from practical application in aqueous solution under ambient conditions, is extremely challenging and requires a rational design of electrocatalytic centers. We observed that bismuth (Bi) might be a promising candidate for this task because of its weak binding with H adatoms, which increases the selectivity and production rate. Furthermore, we successfully synthesized defect‐rich Bi nanoplates as an efficient noble‐metal‐free N 2 reduction electrocatalyst via a low‐temperature plasma bombardment approach. When exclusively using 1 H NMR measurements with N 2 gas as a quantitative testing method, the defect‐rich Bi(110) nanoplates achieved a 15 NH 3 production rate of 5.453 μg mg Bi −1 h −1 and a Faradaic efficiency of 11.68 % at −0.6 V vs. RHE in aqueous solution at ambient conditions.

Propane dehydrogenation (PDH) has great potential to meet the increasing global demand for propylene, but the widely used Pt-based catalysts usually suffer from short-term stability and unsatisfactory propylene selectivity. Herein, we develop a ligand-protected direct hydrogen reduction method for encapsulating subnanometer bimetallic Pt-Zn clusters inside silicalite-1 (S-1) zeolite. The introduction of Zn species significantly improved the stability of the Pt clusters and gave a superhigh propylene selectivity of 99.3 % with a weight hourly space velocity (WHSV) of 3.6-54 h-1 and specific activity of propylene formation of 65.5 mol C3H6 gPt-1 h-1 (WHSV=108 h-1 ) at 550 °C. Moreover, no obvious deactivation was observed over PtZn4@S-1-H catalyst even after 13000 min on stream (WHSV=3.6 h-1 ), affording an extremely low deactivation constant of 0.001 h-1 , which is 200 times lower than that of the PtZn4/Al2 O3 counterpart under the same conditions. We also show that the introduction of Cs+ ions into the zeolite can improve the regeneration stability of catalysts, and the catalytic activity kept unchanged after four continuous cycles.

Abstract The design of cheap, non-toxic, and earth-abundant transition metal catalysts for selective hydrogenation of alkynes remains a challenge in both industry and academia. Here, we report a new atomically dispersed copper (Cu) catalyst supported on a defective nanodiamond-graphene (ND@G), which exhibits excellent catalytic performance for the selective conversion of acetylene to ethylene, i.e., with high conversion (95%), high selectivity (98%), and good stability (for more than 60 h). The unique structural feature of the Cu atoms anchored over graphene through Cu-C bonds ensures the effective activation of acetylene and easy desorption of ethylene, which is the key for the outstanding activity and selectivity of the catalyst.

We present a simple and feasible strategy to synthesize the novel anatase TiO2/graphene composites with exposed TiO2 {001} high-energy facets by the hydrofluoric acid and methanol joint assisted solvothermal reactions. During the synthesis process, graphene was uniformly covered with a large number of anatase TiO2 nanoparticles (20–25 nm), exposing the {001} facets. The X-ray photoelectron spectroscopy and X-ray absorption measurements show the presence of electron transfer between TiO2 and graphene. Furthermore, transient photovoltage spectra of the composite also exhibits prolonged mean lifetime of electron–hole pairs compared with pure TiO2. The electron transfer between Ti and C will greatly retard the recombination of photoinduced charge carriers and prolong electron lifetime, which contribute to the enhancement of photocatalytic performance. During the photocatalysis measurement, the TiO2/graphene composites have high photocatalytic activity compared with the P25 under UV light, likely due to the effective separation of photoinduced charge and exposure of high reactive {001} facets.

Single-atom catalysts (SACs) are efficient for maximizing electrocatalytic activity, but have unsatisfactory activity for the oxygen evolution reaction (OER). Herein, the NaCl template synthesis of individual nickel (Ni) SACs is reported, bonded to oxygen sites on graphene-like carbon (denoted as Ni-O-G SACs) with superior activity and stability for OER. A variety of characterizations unveil that the Ni-O-G SACs present 3D porous framework constructed by ultrathin graphene sheets, single Ni atoms, coordinating nickel atoms to oxygen. Consequently, the catalysts are active and robust for OER with extremely low overpotential of 224 mV at current density of 10 mA cm-2, 42 mV dec-1 Tafel slope, oxygen production turn over frequency of 1.44 S-1 at 300 mV, and long-term durability without significant degradation for 50 h at exceptionally high current of 115 mA cm-1, outperforming the state-of-the-art OER SACs. A theoretical simulation further reveals that the bonding between single nickel and oxygen sites results in the extraordinary boosting of OER performance of Ni-O-G SACs. Therefore, this work opens numerous opportunities for creating unconventional SACs via metal-oxygen bonding.

Single-atom catalysts (SACs) always exhibit distinctive catalytic activities for oxygen reduction/evolution reactions (ORR/OER), making SACs relevant in a number of crucial applications including fuel cells, metal-air batteries, as well as in industrial applications. Recently, fabricating SACs with rich multidimensional nanoarchitectures has become fascinating but challenging. Here, for the first time, we explore a facile and practicable “sacrificed-template” method to prepare cobalt single-atom electrocatalysts with Urchin-like Nano-Tube hierarchical structures (UNT Co SAs/N-C) derived from well-aligned metal-organic-frameworks (MOFs) superstructure (UNT ZIF-67). The as-prepared UNT Co SAs/N-C catalysts exhibit superior performance both in ORR/OER. XAFS and density functional theory (DFT) calculations reveal that outstanding catalytic activities stem from high-quality single-atom dispersion, precise local coordination of CoN4, and well-aligned carbon matrix based on MOFs superstructures. Our work provides new perspective in enriching SACs synthesis methodologies.

A synergistic N doping plus PO43- intercalation strategy is used to induce high conversion (ca. 41 %) of 2H-MoS2 into 1T-MoS2 , which is much higher than single N doping (ca. 28 %) or single PO43- intercalation (ca. 10 %). A scattering mechanism is proposed to illustrate the synergistic phase transformation from the 2H to the 1T phase, which was confirmed by synchrotron radiation and spherical aberration TEM. To further enhance reaction kinetics, the designed (N,PO43- )-MoS2 nanosheets are combined with conductive vertical graphene (VG) skeleton forming binder-free arrays for high-efficiency hydrogen evolution reaction (HER). Owing to the decreased band gap, lower d-band center, and smaller hydrogen adsorption/desorption energy, the designed (N,PO43- )-MoS2 /VG electrode shows excellent HER performance with a lower Tafel slope and overpotential than N-MoS2 /VG, PO43- -MoS2 /VG counterparts, and other Mo-base catalysts in the literature.

The development of new methods for the direct transformation of methanol into two or multi-carbon compounds via controlled carbon-carbon coupling is a highly attractive but challenging goal. Here, we report the first visible-light-driven dehydrogenative coupling of methanol into ethylene glycol, an important chemical currently produced from petroleum. Ethylene glycol is formed with 90% selectivity and high efficiency, together with hydrogen over a molybdenum disulfide nanofoam-modified cadmium sulfide nanorod catalyst. Mechanistic studies reveal a preferential activation of C-H bond instead of O-H bond in methanol by photoexcited holes on CdS via a concerted proton-electron transfer mechanism, forming a hydroxymethyl radical (⋅CH2OH) that can readily desorb from catalyst surfaces for subsequent coupling. This work not only offers an alternative nonpetroleum route for the synthesis of EG but also presents a unique visible-light-driven catalytic C-H activation with the hydroxyl group in the same molecule keeping intact.

Fischer-Tropsch synthesis (FTS) is a promising technology to convert syngas derived from non-petroleum-based resources to valuable chemicals or fuels. Selectively producing target products will bring great economic benefits, but unfortunately it is theoretically limited by Anderson-Schulz-Flory (ASF) law. Herein, we synthesize size-uniformed cobalt nanocrystals embedded into mesoporous SiO2 supports, which is likely the structure of water-melon seeds inside pulps. We successfully tune the selectivity of products from diesel-range hydrocarbons (66.2%) to gasoline-range hydrocarbons (62.4%) by controlling the crystallite sizes of confined cobalt from 7.2 to 11.4 nm, and modify the ASF law. Generally, larger Co crystallites increase carbon-chain growth, producing heavier hydrocarbons. But here, we interestingly observe a reverse phenomenon: the uniformly small-sized cobalt crystallites can strongly adsorb active C* species, and the confined structure will inhibit aggregation of cobalt crystallites and escape of reaction intermediates in FTS, inducing the higher selectivity towards heavier hydrocarbons.

Efficient electrocatalysts for oxygen evolution reaction (OER) in acid are critical to the development of clean energy conversion schemes. Lattice-oxygen-mediated mechanism (LOM) has been developed to boost OER kinetic via triggering lattice oxygen redox. However, the promoted intrinsic activity is compromised by low stability due to bulk structure reconstruction during OER. Here, we demonstrate that a single-site Ir-doping strategy can effectively address this challenge. Attributing to the carefully defined chelation environment of Ir, increased Ir–O covalency and engaged lattice oxygen oxidation have been observed. More importantly, locally triggered LOM introduces no structure evolution during OER. As a result, the constructed catalyst (Ir–MnO2) exhibited over 42 times more mass activity than that of commercial IrO2 as well as over 650 h stability with only a 15 mV increase in overpotential. Our work opens up a feasible strategy to boost OER activity and stability simultaneously.

Strong metal-support interaction (SMSI) has been regarded as one of the most important concepts in heterogeneous catalysis, which has been almost exclusively discussed in metal/oxide catalysts. Here, we show that gold/molybdenum carbide (Au/MoC x) catalysts feature highly dispersed Au overlayers, strong interfacial charge transfer between metal and support, and excellent activity in the low-temperature water-gas shift reaction (LT-WGSR), demonstrating the active SMSI state. Subsequent oxidation treatment results in strong aggregation of Au nanoparticles, weak interfacial electronic interaction, and poor LT-WGSR activity. The two interface states can be transformed into each other by alternative carbonization and oxidation treatments. This work reveals the active SMSI effect in metal/carbide catalysts induced by carbonization, which opens a new territory for this important concept.

Defect engineering is a promising strategy to enhance light absorption and charge separation of photocatalysts. Herein, we simply tailor the quantity and distribution of oxygen vacancies, as one of typical defects, on surface or bulk of thermal-treated WO3 in the different H2 concentration. The quantity of bulk oxygen vacancies on WO3 consistently rises with the increased H2 concentration, while that of surface oxygen vacancies presents a volcano-type variation. The sample of WO3-H20, thermal-pretreated in 20% H2, contains the largest amount of surface oxygen vacancies. Our results show that both surface and bulk oxygen vacancies on WO3 can promote the visible light photocatalytic activity in water splitting, however, in different ways. Bulk oxygen vacancies mainly promote the visible light harvesting and slightly restrain the electrons and holes recombination by narrowing band gap energy (Eg), while surface oxygen vacancies significantly increase the charge-carriers separation efficiency by lowering valence band edge (VBE). Compared with the light absorption, the separation of electrons and holes is more critical in photocatalytic oxygen evolution over WO3, revealing the more decisive role of surface oxygen vacancies than bulk oxygen vacancies. Expectedly, WO3-H20 shows the highest charge-carriers separation efficiency and visible light photocatalytic performance. Our work provides a new insight into designing of efficient defect-engineered semiconductors for the related solar light utilization processes.

This paper describes the effects of defect distribution on energy band structure and the subsequent photocatalytic activity over TiO2 with exposed {001} facets as the model catalyst. Our results show that only surface oxygen vacancies (Vo’s) and Ti3+ centers in TiO2 can be induced by hydrogenation treatment, whereas the generation of bulk Vo’s and Ti3+ species depends on the thermal treatment in nitrogen. Both the surface and bulk defects in TiO2 can promote the separation of electron-hole pairs, enhance the light absorption, and increase the donor density. The presence of surface and bulk defects in TiO2 can not change the valence band maximum, but determine the conduction band minimum. Surface defects in TiO2 induce a tail of conduction band located above the H+/H2 redox potential, which benefits the photocatalytic performance. However, bulk defects in TiO2 generate a band tail below the H+/H2 potential, which inhibits hydrogen production. Thus, the change of band gap structure by defects is the major factor to determine the photocatalytic activity of TiO2 for hydrogen evolution. It is a new insight into the rational design and controllable synthesis of defect-engineered materials for various catalytic processes.

The applications of the most promising Fe-N-C catalysts are prohibited by their limited intrinsic activities. Manipulating the Fe energy level through anchoring electron-withdrawing ligands is found effective in boosting the catalytic performance. However, such regulation remains elusive as the ligands are only uncontrollably introduced oweing to their energetically unstable nature. Herein, we report a rational manipulation strategy for introducing axial bonded O to the Fe sites, attained through hexa-coordinating Fe with oxygen functional groups in the precursor. Moreover, the O modifier is stabilized by forming the Fe-O-Fe bridge bond, with the approximation of two FeN4 sites. The energy level modulation thus created confers the sites with an intrinsic activity that is over 10 times higher than that of the normal FeN4 site. Our finding opens a novel strategy to manage coordination environments at an atomic level for high activity ORR catalysts.

Methanol–water reforming is a promising solution for H2 production/transportation in stationary and mobile hydrogen applications. Developing inexpensive catalysts with sufficiently high activity, selectivity, and stability remains challenging. In this paper, nickel-supported over face-centered cubic (fcc) phase α-MoC has been discovered to exhibit extraordinary hydrogen production activity in the aqueous-phase methanol reforming reaction. Under optimized condition, the hydrogen production rate of 2% Ni/α-MoC is about 6 times higher than that of conventional noble metal 2% Pt/Al2O3 catalyst. We demonstrate that Ni is atomically dispersed over α-MoC via carbon bridge bonds, forming a Ni1–Cx motif on the carbide surface. Such Ni1–Cx motifs can effectively stabilize the isolated Ni1 sites over the α-MoC substrate, rendering maximized active site density and high structural stability. In addition, the synergy between Ni1–Cx motif and α-MoC produces an active interfacial structure for water dissociation, methanol activation, and successive reforming processes with compatible activity.

Tin-assisted fully exposed Pt clusters are fabricated on the core–shell nanodiamond@graphene (ND@G) hybrid support (a-PtSn/ND@G). The obtained atomically dispersed Pt clusters, with an average Pt atom number of 3, were anchored over the ND@G support by the assistance of Sn atoms as a partition agent and through the Pt–C bond between Pt clusters and defect-rich graphene nanoshell. The atomically dispersed Pt clusters guaranteed a full metal availability to the reactants, a high thermal stability, and an optimized adsorption/desorption behavior. It inhibits the side reactions and enhances catalytic performance in direct dehydrogenation of n-butane at a low temperature of 450 °C, leading to >98% selectivity toward olefin products, and the turnover frequency (TOF) of a-PtSn/ND@G is ∼3.9 times higher than that of the traditional Pt3Sn alloy catalyst supported on Al2O3 (Pt3Sn/Al2O3).

Cobalt carbide (Co2C) has recently been reported to be efficient for the conversion of syngas (CO+H2) to lower olefins (C2–C4) and higher alcohols (C2+ alcohols); however, its properties and formation conditions remain ambiguous. On the basis of our previous investigations concerning the formation of Co2C, the work herein was aimed at defining the mechanism by which the manganese promoter functions in the Co-based catalysts supported on activated carbon (CoxMn/AC). Experimental studies validated that Mn facilitates the dissociation and disproportionation of CO on the surface of catalyst and prohibits H2 adsorption to some extent, creating a relative C-rich and H-lean surface chemical environment. We advocate that the surface conditions result in the transformation from metallic Co to Co2C phase under realistic reaction conditions to form Co@Co2C nanoparticles, in which residual small Co0 ensembles (<6 nm) distribute on the surface of Co2C nanoparticles (∼20 nm). Compared with the Co/AC catalyst, where the active site is composed of Co2C phase on the surface of Co0 nanoparticles (Co2C@Co), the Mn-promoted catalysts (Co@Co2C) displayed much higher olefin selectivity (10% versus 40%), while the selectivity to alcohols over the two catalysts are similar (∼20%). The rationale behind the strong structure–performance relationship is twofold. On the one hand, Co–Co2C interfaces exist universally in the catalysts, where synergistic effects between metallic Co and Co2C phase occur and are responsible for the formation of alcohols. On the other hand, the relative C-rich and H-lean surface chemical environment created by Mn on the Co@Co2C catalysts facilitates the formation of olefins.

Investigating on well-defined structure-engineering and atomic arrangement of fuel cell catalysts with high activity has attracted considerable research interest the last decade. Specially, unique nanostructures, which possess high surface-to-volume ratio and high atomic utilization have been emerged as promising candidate catalysts. Herein, we have successfully synthesized Pt–Ni cross double dumbbell-like nanostructures (Pt-Ni CDDNs) via a facile one-pot synthesis route and a kinetic control with surface capping. It is found that the as-prepared Pt–Ni alloy nanostructures exhibit an enhanced catalytic activity toward oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) in comparison with commercial Pt/C catalysts. The excellent electrooxidation property is attributed to the synergistic effect between Pt and Ni atoms, as well as high specific surface area of dumbbell-like nanostructures with multiple nanosheets. The present work provides new opportunities for the rational design of bimetallic nanomaterials with enhanced catalytic performance.

Abstract Introducing cerium (Ce) species into electrocatalysts has been recently developed as an effective approach to improve their oxygen evolution reaction (OER) performance. Importantly, the spatial distribution of Ce species in the hosts can determine the availability of Ce species either as additives or as co‐catalysts, which would dictate their different contributions to the enhanced electrocatalytic performance. Herein, the comprehensive investigations on two different catalyst configurations, namely CeO 2 ‐embedded NiO (Ce‐NiO‐E) and CeO 2 ‐surface‐loaded NiO (Ce‐NiO‐L), are performed to understand the effect of their specific spatial arrangements on OER characteristics. The Ce‐NiO‐E catalysts exhibit a smaller overpotential of 382 mV for 10 mA cm −2 and a lower Tafel slope of 118.7 mV dec −1 , demonstrating the benefits of the embedded configuration for OER, as compared with those of Ce‐NiO‐L (426 mV and 131.6 mV dec −1 ) and pure NiO (467 mV and 140.7 mV dec −1 ), respectively. The improved OER property of Ce‐NiO‐E originates from embedding small‐sized CeO 2 clusters into the host for the larger specific surface area, richer surface defects, higher oxygen adsorption capacity, and better optimized electronic structures of the surface active sites, as compared with Ce‐NiO‐L. Above findings provide a valuable guideline for and insight in designing catalysts with different spatial configurations for enhanced catalytic properties.

Abstract Electrochemical reduction of carbon dioxide (CO 2 ) is a promising approach to solve both renewable energy storage and carbon‐neutral energy cycles, while the capability of selective reduction to C 2+ products has still been quite limited. In this work, partially reduced copper oxide nanodendrites with rich surface oxygen vacancies (CuO x –Vo) are developed, serving as excellent Lewis base sites for enhanced CO 2 adsorption and subsequent electrochemical reduction. Theoretical calculations reveal that these oxygen vacancy‐rich CuO x surfaces provide strong binding affinities to the intermediates of *CO and *COH, but weak affinity to *CH 2 , thus leading to efficient formation of C 2 H 4 . As a result, the partially reduced CuO x nanodendrites exhibit one of the highest C 2 H 4 production Faradaic efficiencies of 63%. The electrochemical stability test further shows that the C 2 H 4 Faradaic efficiency strongly depends on the oxygen vacancy density in CuO x , which can further be regenerated for several cycles, thus suggesting the critical role of oxygen vacancies for the C 2 product selectivity.

Abstract Single-atom metal-nitrogen-carbon (M-N-C) catalysts have sparked intensive interests, however, the development of an atomically dispersed metal-phosphorus-carbon (M-P-C) catalyst has not been achieved, although molecular metal-phosphine complexes have found tremendous applications in homogeneous catalysis. Herein, we successfully construct graphitic phosphorus species coordinated single-atom Fe on P-doped carbon, which display outstanding catalytic performance and reaction generality in the heterogeneous hydrogenation of N-heterocycles, functionalized nitroarenes, and reductive amination reactions, while the corresponding atomically dispersed Fe atoms embedded on N-doped carbon are almost inactive under the same reaction conditions. Furthermore, we find that the catalytic activity of graphitic phosphorus coordinated single-atom Fe sharply decreased when Fe atoms were transformed to Fe clusters/nanoparticles by post-impregnation Fe species. This work can be of fundamental interest for the design of single-atom catalysts by utilizing P atoms as coordination sites as well as of practical use for the application of M-P-C catalysts in heterogeneous catalysis.

Metal nanoparticle (NP), cluster and isolated metal atom (or single atom, SA) exhibit different catalytic performance in heterogeneous catalysis originating from their distinct nanostructures. To maximize atom efficiency and boost activity for catalysis, the construction of structure-performance relationship provides an effective way at the atomic level. Here, we successfully fabricate fully exposed Pt3 clusters on the defective nanodiamond@graphene (ND@G) by the assistance of atomically dispersed Sn promoters, and correlated the n-butane direct dehydrogenation (DDH) activity with the average coordination number (CN) of Pt-Pt bond in Pt NP, Pt3 cluster and Pt SA for fundamentally understanding structure (especially the sub-nano structure) effects on n-butane DDH reaction at the atomic level. The as-prepared fully exposed Pt3 cluster catalyst shows higher conversion (35.4%) and remarkable alkene selectivity (99.0%) for n-butane direct DDH reaction at 450 °C, compared to typical Pt NP and Pt SA catalysts supported on ND@G. Density functional theory calculation (DFT) reveal that the fully exposed Pt3 clusters possess favorable dehydrogenation activation barrier of n-butane and reasonable desorption barrier of butene in the DDH reaction.

Abstract Engineering the reaction interface to preferentially attract reactants to inner Helmholtz plane is highly desirable for kinetic advancement of most electro-catalysis processes, including hydrogen evolution reaction (HER). This, however, has rarely been achieved due to the inherent complexity for precise surface manipulation down to molecule level. Here, we build a MoS 2 di-anionic surface with controlled molecular substitution of S sites by –OH. We confirm the –OH group endows the interface with reactant dragging functionality, through forming strong non-covalent hydrogen bonding to the reactants (hydronium ions or water). The well-conditioned surface, in conjunction with activated sulfur atoms (by heteroatom metal doping) as active sites, giving rise to up-to-date the lowest over potential and highest intrinsic activity among all the MoS 2 based catalysts. The di-anion surface created in this study, with atomic mixing of active sites and reactant dragging functionalities, represents a effective di-functional interface for boosted kinetic performance.

Abstract A competitive complexation strategy has been developed to construct a novel electrocatalyst with Zn‐Co atomic pairs coordinated on N doped carbon support (Zn/CoN‐C). Such architecture offers enhanced binding ability of O 2 , significantly elongates the O−O length (from 1.23 Å to 1.42 Å), and thus facilitates the cleavage of O−O bond, showing a theoretical overpotential of 0.335 V during ORR process. As a result, the Zn/CoN‐C catalyst exhibits outstanding ORR performance in both alkaline and acid conditions with a half‐wave potential of 0.861 and 0.796 V respectively. The in situ XANES analysis suggests Co as the active center during the ORR. The assembled zinc–air battery with Zn/CoN‐C as cathode catalyst presents a maximum power density of 230 mW cm −2 along with excellent operation durability. The excellent catalytic activity in acid is also verified by H 2 /O 2 fuel cell tests (peak power density of 705 mW cm −2 ).

Developing efficient catalysts for steering the electrochemical CO2 reduction reaction (CO2RR) toward high-value chemicals beyond CO and formic acid is highly desirable. Herein, we have developed copper-based catalysts confined within a rationally designed covalent triazine framework (CTF-B), featuring a CuN2Cl2 structure, for selective CO2RR to hydrocarbons with a maximum Faradaic efficiency (FE) of 81.3% and an FE of C2H4 up to 30.6%. Operando X-ray adsorption fine structure analyses reveal the potential-driven dynamic formation of Cu atomic clusters, together with the time-dependent and Cu-content-dependent CO2RR performance associated with the catalyst activation, definitively uncovering that the aggregated Cu clusters confined within CTF-B are the active sites. A further probing experiment of CO electroreduction not only verifies that CO is one of the key intermediates for the CO2RR but also demonstrates the improved selectivity to C2 chemicals, with a maximum FE of 68.4% (C2H4, 35.0%; acetate, 33.4%), possibly originating from the accelerative C–C coupling reaction due to the increased CO coverage and enhanced local pH in CO-saturated electrolyte. Interestingly, acetate is identified as the only liquid product, mostly likely benefiting from the dominant low-coordination active sites of confined Cu aggregation and favorable chemical confinement environment of CTF-B. The strategy of constructing efficient metalloelectrocatalysts by means of confinement in a covalent organic framework along with operando identification of active sites sheds light on the rational catalyst design and structure–property relationship.

High-loaded Pt1Co1-IMC@Pt/C catalyst enables high power PEMFCs, meeting the practical application requirement in electric vehicles.

Proton-exchange membrane fuel cells (PEMFCs) are limited by their extreme sensitivity to trace-level CO impurities, thus setting a strict requirement for H2 purity and excluding the possibility to directly use cheap crude hydrogen as fuel. Herein, we report a proof-of-concept study, in which a novel catalyst comprising both Ir particles and Ir single-atom sites (IrNP @IrSA -N-C) addresses the CO poisoning issue. The Ir single-atom sites are found not only to be good CO oxidizing sites, but also excel in scavenging the CO molecules adsorbed on Ir particles in close proximity, thereby enabling the Ir particles to reserve partial active sites towards H2 oxidation. The interplay between Ir nanoparticles and Ir single-atom centers confers the catalyst with both excellent H2 oxidation activity (1.19 W cm-2 ) and excellent CO electro-oxidation activity (85 mW cm-2 ) in PEMFCs; the catalyst also tolerates CO in H2 /CO mixture gas at a level that is two times better than that of the current best PtRu/C catalyst.

Copper-based materials are efficient electrocatalysts for the conversion of CO2 to C2+ products, and most these materials are reconstructed in situ to regenerate active species. It is a challenge to precisely design precatalysts to obtain active sites for the CO2 reduction reaction (CO2 RR). Herein, we develop a strategy based on local sulfur doping of a Cu-based metal-organic framework precatalyst, in which the stable Cu-S motif is dispersed in the framework of HKUST-1 (S-HKUST-1). The precatalyst exhibits a high ethylene selectivity in an H-type cell with a maximum faradaic efficiency (FE) of 60.0 %, and delivers a current density of 400 mA cm-2 with an ethylene FE up to 57.2 % in a flow cell. Operando X-ray absorption results demonstrate that Cuδ+ species stabilized by the Cu-S motif exist in S-HKUST-1 during CO2 RR. Density functional theory calculations indicate the partially oxidized Cuδ+ at the Cu/Cux Sy interface is favorable for coupling of the *CO intermediate due to the modest distance between coupling sites and optimized adsorption energy.

Abstract The poor stability of Ru-based acidic oxygen evolution (OER) electrocatalysts has greatly hampered their application in polymer electrolyte membrane electrolyzers (PEMWEs). Traditional understanding of performance degradation centered on influence of bias fails in describing the stability trend, calling for deep dive into the essential origin of inactivation. Here we uncover the decisive role of reaction route (including catalytic mechanism and intermediates binding strength) on operational stability of Ru-based catalysts. Using MRuO x (M = Ce 4+ , Sn 4+ , Ru 4+ , Cr 4+ ) solid solution as structure model, we find the reaction route, thereby stability, can be customized by controlling the Ru charge. The screened SnRuO x thus exhibits orders of magnitude lifespan extension. A scalable PEMWE single cell using SnRuO x anode conveys an ever-smallest degradation rate of 53 μV h −1 during a 1300 h operation at 1 A cm −2 .

Nature-inspired artificial Z-scheme photocatalyst offers great promise in solar overall water splitting, but its rational design, construction and interfacial charge transfer mechanism remain ambiguous. Here, we design an approach of engineering interfacial band bending via work function regulation, which realizes directional charge transfer at interface and affords direct Z-scheme pathway. Taking BiVO4 as prototype, its oxygen vacancy concentration is reduced by slowing down the crystallization rate, thereby changing the work function from smaller to larger than that of polymeric carbon nitride (PCN). Consequently, the photoinduced charge transfer pathway of BiVO4/PCN is switched from type-II to Z-scheme as evidenced by synchronous illuminated X-ray photoelectron spectroscopy (XPS) and femtosecond transient absorption spectroscopy. Specifically, the direct Z-scheme BiVO4/PCN shows superior photocatalytic performance in water splitting. This work provides deep insights and guidelines to constructing heterojunction photocatalysts for solar utilization.

Converting nitrate to ammonia (NH 3 ) with the use of electricity produced from renewable energy provides an alternative and sustainable route for NH 3 synthesis under ambient conditions. However, due to the complex mechanism involving eight electrons and nine protons transfer processes in nitrate-to-ammonia conversion, reactions run with Cu-based catalysts for NH 3 often exhibit limited selectivity and yield. Here, we report a single-atom Ni-alloyed Cu catalyst that exclusively converts nitrate into NH 3 with a maximum Faradaic efficiency of ~100% and a yield rate of 326.7 μmol h −1 cm −2 at − 0.55 V versus reversible hydrogen electrode (RHE). X-ray absorption fine structure evidence and density functional theory calculations reveal that the activated single Ni atom on the Cu catalyst regulates the third protonation step of the electrocatalytic nitrate reduction reaction (eNO 3 - RR) and increases the interaction between the Ni atom and the crucial NOOH* intermediate, thus decreasing the limiting potential and inhibiting byproduct formation. A rough estimation suggests that the price of fertilizer produced by this single-atom alloyed catalyst through the eNO 3 - RR is competitive with the Haber-Bosch process. Electrocatalytic nitrate reduction constitutes an alternative and sustainable route for NH 3 synthesis under ambient conditions. Here, the authors present a single-atom Ni-alloyed Cu electrocatalyst that exclusively converts nitrate into NH 3 with a maximum Faradaic efficiency of ~100%. • A single-atom Ni-alloyed Cu electrocatalyst that specifically converts nitrate into NH 3 . • A maximum Faradaic efficiency of ~100% can be achieved on Ni 1 Cu-SAA. • Incorporated single Ni atom decreases the limiting potential and inhibits byproduct formation. • Fertilizer prices produced by eNO 3 - RR on Ni 1 Cu-SAA are competitive with the Haber-Bosch process.

Abstract Pursuing and developing effective methodologies to construct highly active catalytic sites to maximize the atomic and energy efficiency by material engineering are attractive. Relative to the tremendous researches of carbon-based single atom systems, the construction of bio-applicable single atom materials is still in its infancy. Herein, we propose a facile and general interfacial-confined coordination strategy to construct high-quality single-atom nanotherapeutic agent with Fe single atoms being anchored on defective carbon dots confined in a biocompatible mesoporous silica nanoreactor. Furthermore, the efficient energy conversion capability of silica-based Fe single atoms system has been demonstrated on the basis of the exogenous physical photo irradiation and endogenous biochemical reactive oxygen species stimulus in the confined mesoporous network. More importantly, the highest photothermal conversion efficiency with the mechanism of increased electron density and narrow bandgap of this single atom structure in defective carbon was proposed by the theoretical DFT calculations. The present methodology provides a scientific paradigm to design and develop versatile single atom nanotherapeutics with adjustable metal components and tune the corresponding reactions for safe and efficient tumor therapeutic strategy.

The contribution of the reverse spillover effect to hydrogen generation reactions is still controversial. Herein, the promotion functions for reverse spillover in the ammonia borane hydrolysis reaction are proven by constructing a spatially separated NiO/Al2O3/Pt bicomponent catalyst via atomic layer deposition and performing in situ quick X-ray absorption near-edge structure (XANES) characterization. For the NiO/Al2O3/Pt catalyst, NiO and Pt nanoparticles are attached to the outer and inner surfaces of Al2O3 nanotubes, respectively. In situ XANES results reveal that for ammonia borane hydrolysis, the H species generated at NiO sites spill across the support to the Pt sites reversely. The reverse spillover effects account for enhanced H2 generation rates for NiO/Al2O3/Pt. For the CoOx/Al2O3/Pt and NiO/TiO2/Pt catalysts, reverse spillover effects are also confirmed. We believe that an in-depth understanding of the reverse effects will be helpful to clarify the catalytic mechanisms and provide a guide for designing highly efficient catalysts for hydrogen generation reactions.

A hydrophobic core–shell architecture was constructed to control local H 2 O availability on the surface of the copper-based materials, which could provide a maximum generation rate of −434 mA cm −2 towards CH 4 .

Covalent organic frameworks linked by CC bonds have gained great attention for various application, and their fully conjugated skeletons were potentially conversed into two-dimensional (2D) carbons. Herein, we described a novel strategy to fabricate 2D carbon nanorods from a sp2 carbon linked COF, which had a high surface area of 804.8 m2 g−1. The one-dimensional channels confined the Fe ions during pyrolysis, which facilitated to form ultra-close atomic sites. The resulting catalyst displayed high catalytic activity towards oxygen reduction reaction, with a half-wave potential of 0.82 V and a mass activity of 4087.9 mA mg−1 at 0.7 V versus RHE, which were high than those of Pt/C (0.81 V and 126.3 mA mg−1). The theoretical calculation revealed the close FeN4 sites achieved a lower *OH adsorption energy than isolated FeN4 sites. This work provides a new insight into developing single atom catalysts from COFs.

Atomically dispersed platinum clusters are developed as a novel single atom co-catalyst, which dramatically enhances the photocatalytic H 2 production rate.

Two-dimensional covalent organic frameworks (2D COFs) are often employed for electrocatalytic systems because of their structural diversity. However, the efficiency of atom utilization is still in need of improvement, because the catalytic centers are located in the basal layers and it is difficult for the electrolytes to access them. Herein, we demonstrate the use of 1D COFs for the 2e- oxygen reduction reaction (ORR). The use of different four-connectivity blocks resulted in the prepared 1D COFs displaying good crystallinity, high surface areas, and excellent chemical stability. The more exposed catalytic sites resulted in the 1D COFs showing large electrochemically active surface areas, 4.8-fold of that of a control 2D COF, and thus enabled catalysis of the ORR with a higher H2 O2 selectivity of 85.8 % and activity, with a TOF value of 0.051 s-1 at 0.2 V, than a 2D COF (72.9 % and 0.032 s-1 ). This work paves the way for the development of COFs with low dimensions for electrocatalysis.

MXene basal planes are generally considered catalytically inert, due to the passivation by inactive surface groups. However, theoretical calculation predicates that MXene basal planes can become active by tuning its terminal groups. The above understandings are ambiguous on whether the MXene basal planes are indeed electrocatalytically active, and in turn what are the true active sites on MXene. Herein, we functionalized Ti3C2 MXene by introducing terminal oxygen groups to reveal the active sites and probe the reaction mechanism for electrocatalytic nitrate reduction reaction (eNO3-RR). On the basis of the data presented, the in situ transformed surface hydroxyl groups were identified as a new active site for nitrate reduction. A novel reaction mechanism involving hydrogen-bonding (H-bonding) between nitrate and the -OH groups on the Ti3C2 MXene basal plane was proposed, which adequately explained the high applied potentials and low selectivity for HER on the OH-terminated Ti3C2 MXene during eNO3-RR. This hydrogen-bonding-mediated process is likely applicable to a wide range of other materials and reactions.

Abstract The electrochemical carbon dioxide reduction reaction (CO 2 RR) for high‐value‐added products is a promising strategy to tackle excessive CO 2 emissions. However, the activity of and selectivity for catalysts for CO 2 RR still need to be improved because of the competing reaction (hydrogen evolution reaction). In this study, for the first time, we have demonstrated dual atomic catalytic sites for CO 2 RR from a core–shell hybrid of the covalent–organic framework and the metal–organic framework. Due to abundant dual atomic sites (with CoN 4 O and ZnN 4 of 2.47 and 11.05 wt.%, respectively) on hollow carbon, the catalyst promoted catalysis of CO 2 RR, with the highest Faradic efficiency for CO of 92.6% at –0.8 V and a turnover frequency value of 1370.24 h –1 at –1.0 V. More importantly, the activity and selectivity of the catalyst were well retained for 30 h. The theoretical calculation further revealed that CoN 4 O was the main site for CO 2 RR, and the activity of and selectivity for Zn sites were also improved because of the synergetic roles.

Metal-nitrogen-carbon materials are the most promising platinum replacement catalysts for oxygen reduction reaction. However, lacking an efficient approach to improve durability—i.e., to cope with the attack by in situ formed radicals, leaching of central ions, etc.—has limited these catalysts from widespread application. Herein we present a novel, dual-metal, single-atom catalyst design (Fe,Ce-N-C) to confront the formidable deactivation issue of the best-performing yet unstable Fe-N-C catalysts. Cerium single sites are revealed as efficient chemical catalysts to catalyze the H2O2 disproportionation into O2, leading to increased 4e selectivity. Moreover, rather than Fe single sites that catalyze the formation of reactive ·OH and ·OOH species, these cerium single sites act proactively to eliminate in situ-generated radicals. The final Fe,Ce-N-C catalyst represents excellent durability exceeding that of Fe-N-C. This work opens a new path to alleviate the degradation of Fe-N-C catalysts in an acidic medium.

Maintaining the stability of single-atom catalysts in high-temperature reactions remains extremely challenging because of the migration of metal atoms under these conditions. We present a strategy for designing stable single-atom catalysts by harnessing a second metal to anchor the noble metal atom inside zeolite channels. A single-atom rhodium-indium cluster catalyst is formed inside zeolite silicalite-1 through in situ migration of indium during alkane dehydrogenation. This catalyst demonstrates exceptional stability against coke formation for 5500 hours in continuous pure propane dehydrogenation with 99% propylene selectivity and propane conversions close to the thermodynamic equilibrium value at 550°C. Our catalyst also operated stably at 600°C, offering propane conversions of >60% and propylene selectivity of >95%.

Metal–biopolymer complexes has recently gained significant attention as an effective adsorbent used for the removal of Cr(VI) from water. Unfortunately, despite increasing research efforts in the field of removal efficiency, whether this kind of complex can reduce Cr(VI) to less-toxic Cr(III) and what are the mechanisms of detoxification processes are still unknown. In this study, despite the highly adsorption efficiency (maximum adsorption capacity of 173.1 mg/g in 10 min), the significant improvement of Cr(VI) reduction by chitosan–Fe(III) complex compared with normal crosslinked chitoan has been demonstrated. In addition, the structure of chitosan–Fe(III) complex and its functional groups concerned with Cr(VI) detoxification have been characterized by the powerful spectroscopic techniques X-ray absorption fine structure (XAFS) and X-ray photoelectron spectroscopy (XPS). The XPS spectra indicated that the primary alcoholic function on C-6 served as an electron donor during Cr(VI) reduction and was oxidized to a carbonyl group. The X-ray adsorption near edge spectra (XANES) of the Cr(VI)-treated chitosan–Fe(III) complex revealed the similar geometrical arrangement of Cr species as that in Cr(III)-bound chitosan–Fe(III). Overall, a possible process and mechanism for highly efficient detoxification of Cr(VI) by chitosan–Fe(III) complex has been elucidate.

The hydroformylation of propene to linear-butaldehyde can be performed efficiently in a continuous fixed-bed reactor employing the copolymer self-supported heterogeneous Rh/CPOL-bp&amp;P catalysts.

An effective, template-free synthesis methodology has been developed for preparing mesoporous nitrogen-doped SrTiO3 (meso-STON) using glycine as both a nitrogen source and a mesopore creator. The N-doping, large surface area and developed porosity endow meso-STON with excellent activity in visible-light-responsive photodegradation of organic dyes.

Herein, we report the performance of the catalytic combustion of methane over the Ce-doped SnO2 catalysts. Doping with Ce increases the surface areas, decreases the crystallite sizes, and activates both the surface metal cations and surface oxygen species. Upon methane combustion, the surface Sn4+ cations are active sites, and the surface lattice oxygen plays an important role, as well. Kinetics results suggest that the activation energy (Ea) and pre-exponential factor (A) are determined by the reducibility and the area-specific quantity of the surface Sn4+ cations, respectively. The Sn0.7Ce0.3O2 catalyst exhibits the highest area-specific rate because of its lowest Ea and relatively bigger A values. Its turnover frequency is five times higher, as compared with the SnO2. The reaction pathways upon the Sn-rich catalysts (SnO2 phase) follow the Mars–van Krevelen model, while they become more complex upon the Ce-rich ones (CeO2 phase). Additionally, these SnO2-based catalysts display the high water resistance.

In this study, the heterogeneous Fenton degradation of cationic and anionic dyes catalyzed by a series of Cr-containing magnetites (Fe3−xCrxO4, x = 0.00, 0.18, 0.33, 0.47 and 0.67) has been investigated under neutral pH conditions. Methylene blue (MB) and acid orange II (AOII) were chosen as models of cationic and anionic contaminants. Emphases were laid on the comparison of degradation characteristic between MB and AOII and the effect of Cr substitution on the degradation efficiency of both dyes. The octahedral occupancy of Cr3+ increased the BET surface area and superficial hydroxyl amount of magnetite, resulting in an improvement of adsorption ability of MB. However, these Cr-containing magnetites showed no adsorption to AOII. The MB degradation, following the Langmuir–Hinshelwood model, was well fitted by zero-order equation while AOII degradation following the Eley–Rideal model, was well fitted with two-stage pseudo-first-order kinetics. The Cr incorporation significantly improved the catalytic activity of magnetite in heterogeneous Fenton reaction, but the extent of improvement varied with the substitution level. These new insights are of high importance for the environmental application of metal substituted magnetites in the purification of textile wastewater.

Herein, we report a novel carbothermal welding strategy to prepare atomically dispersed Pd sites anchored on a three-dimensional (3D) ZrO2 nanonet (Pd1@ZrO2) via two-step pyrolysis, which were evolved from isolated Pd sites anchored on linker-derived nitrogen-doped carbon (Pd1@NC/ZrO2). First, the NH2-H2BDC linkers and Zr6-based [Zr6(μ3-O)4(μ3-OH)4]12+ nodes of UiO-66-NH2 were transformed into amorphous N-doped carbon skeletons (NC) and ZrO2 nanoclusters under an argon atmosphere, respectively. The NC supports can simultaneously reduce and anchor the Pd sites, forming isolated Pd1-N/C sites. Then, switching the argon to air, the carbonaceous skeletons are gasified and the ZrO2 nanoclusters are welded into a rigid and porous nanonet. Moreover, the reductive carbon will result in abundant oxygen (O*) defects, which could help to capture the migratory Pd1 species, leaving a sintering-resistant Pd1@ZrO2 catalyst via atom trapping. This Pd1@ZrO2 nanonet can act as a semi-homogeneous catalyst to boost the direct synthesis of indole through hydrogenation and intramolecular condensation processes, with an excellent turnover frequency (1109.2 h-1) and 94% selectivity.

Hydrogenation of semiconductors is an efficient way to increase their photocatalytic activity by forming disorder-engineered structures. Herein, we report a facile hydrogenation process of TiO2(B) nanobelts to in situ generate TiO2(B)-anatase heterophase junction with a disordered surface shell. The catalyst exhibits an excellent performance for photocatalytic hydrogen evolution under the simulated solar light irradiation (∼580 μmol h(-1), 0.02 g photocatalyst). The atomically well-matched heterophase junction, along with the disorder-engineered surface shell, promotes the separation of electron-hole and inhibits their recombination. This strategy can be further employed to design other disorder-engineered composite photocatalysts for solar energy utilization.

Nanorod-like TiO2 photocatalysts with controllable particle size for hydrogen production were synthesized based on H2Ti3O7 precursors using hydrothermal and ion exchange methods. The characteristics of TiO2 photocatalysts, such as morphology, specific areas and crystalline quality, can be adjusted by changing hydrothermal conditions, thus optimizing its photocatalytic activity for hydrogen evolution. The TiO2 nanorod possesses the highest photocatalytic activity, even higher than P25, when the hydrothermal temperature is 140 °C, which should be ascribed to its large specific area and good crystalline quality. Non-noble metal Cu as a substitute of Pt was loaded on the surface of TiO2 nanorod to promote the photocatalytic hydrogen production. It was confirmed that, during the photocatalytic reaction process, Cu0 rather than CuOx acted as active sites to enhance the photocatalytic activity. The highest photocatalytic H2 evolution rate of Cu/TiO2 reaches 1023.8 μmol·h−1 when the amount of loading is 0.1 wt%, reaching the 20 times of that of bare TiO2 (49.4 μmol·h−1) and approaching that of Pt/TiO2 (1161.7 μmol·h−1). Non-noble metal Cu not only facilitated the separation of carriers, but reduced the overpotential of hydrogen evolution, thus promoting the photocatalytic activity for hydrogen production.

A series of dually substituted perovskite catalysts La1−xKxCo1−yPdyO3−δ (x = 0, 0.1; y = 0, 0.05) were successfully synthesized through a citrate-based sol–gel process, and employed for soot combustion in the presence of NOx. The physicochemical properties of them were systematically characterized by N2-sorption, XRD, XPS, SEM, HRTEM, XANES, EXAFS, H2-TPR, soot-TPR, FT-IR and TG/DTA. The activity evaluation results show that among all catalysts La0.9K0.1Co0.95Pd0.05O3−δ possesses the highest performance, exhibiting the lowest Ti and Tm (219 ̊C and 360 ̊C), the narrowest temperature range (Tf − Ti = 162 ̊C) and the lowest activation energy (93.6 kJ/mol) for soot combustion. The catalyst La0.9K0.1Co0.95Pd0.05O3−δ shows relatively larger BET surface area, smaller crystallite size and higher dispersion of Pd. Additionally, this catalyst also possesses the best reducibility and highest oxidibility as revealed by H2-TPR and soot-TPR. The Pd ions with high valence (Pd3+, Pd4+) in distorted octahedral coordination environment as demonstrated by XPS, XANES and EXAFS are much more active for NO oxidation and soot combustion than the bivalent Pd ions with square-planar coordination symmetry. Based upon the characterization results and catalytic performance, a mechanism containing two reaction pathways namely direct soot oxidation by surface adsorbed oxygen species in oxygen vacancies and the NO2-assisted soot oxidation is proposed.

Abstract Electrochemical conversion of CO 2 and H 2 O into syngas is an attractive route to utilize green electricity. A competitive system economy demands development of cost‐effective electrocatalyst with dual active sites for CO 2 reduction reaction (CO 2 RR) and hydrogen evolution reaction (HER). Here, a single atom electrocatalyst derived from a metal–organic framework is proposed, in which Co single atoms and N functional groups function as atomic CO 2 RR and HER active sites, respectively. The synthesis method is based on pyrolysis of ZnO@ZIF (zeolitic imidazolate framework). The excess in situ Zn evaporation effectively prevents Co single atoms (≈3.4 wt%) from aggregation and maintains appropriate Co/N ratio. The as‐prepared electrocatalyst is featured with high graphitic degree of carbon support for rapid electron transport and sponge‐like thin carbon shells with hierarchical pore system for facilitating active site exposure and mass transport. Therefore, the electrocatalyst exhibits a nearly 100% Faradic efficiency and a high formation rate of ≈425 mmol g −1 h −1 at 1.0 V with the gaseous product ratio (CO/H 2 ) approximating ideal 1/2. With the assistance of an extensive material characterization and density functional theory (DFT) calculations, it is identified that Co single atoms are uniformly coordinated in the form of Co–C 2 N 2 moieties, and act as the major catalytic sites for CO 2 reduction.

This study investigated the methylene blue (MB) decolorization through heterogeneous UV-Fenton reaction catalyzed by V-Ti co-doped magnetites, with emphasis on comparing the contribution of V and Ti cations on improving the adsorption and catalytic activity of magnetite. In the well crystallized spinel structure, both Ti(4+) and V(3+) occupied the octahedral sites. Ti(4+) showed a more obvious effect on increasing specific surface area and superficial hydroxyl amount than V(3+) did, resulting in a significant improvement of the adsorption ability of magnetite to MB. The UV introduction greatly accelerated MB degradation. And magnetite with more Ti and less V displayed better catalytic activity in MB degradation through heterogeneous UV-Fenton reaction. The transformation of degradation products and individual contribution from vanadium and titanium on improving adsorption and catalytic activity of magnetite were also investigated. These new insights are of high importance for well understanding the interface interaction between contaminants and metal doped magnetites, and the environmental application of natural and synthetic magnetites.

Pt single atoms have unique power in enhancing and accelerating OER active NiOOH phase transformation from NiO.

Hydrogenation-induced surface disorder on semiconductors has been proved an efficient strategy in photocatalysis, but identification and understanding of surface and subsurface disordered layers from molecular level viewpoints are still unclear. Herein, we fabricate efficient disorder-engineered CaTiO3 nanosheets photocatalysts and illustrate functions of surface and subsurface oxygen vacancies on photocatalytic hydrogen evolution. Our experimental and theoretical results reveal that subsurface oxygen vacancies can change energy band structure of CaTiO3 to form band tail states, improving charge separation; and surface oxygen vacancies can act as active centers to facilitate H2 formation. Both merits promote ∼49 times of the hydrogen evolution rate than pristine CaTiO3. In addition, we discover that improving charge separation with subsurface oxygen vacancies is more important than promoting surface reactions with surface oxygen vacancies in defect-engineered photocatalysts. Our work provides new insights into the hydrogenated disordered surface layer, as well as the rational design of photocatalysts with defect-engineering strategies.

Methanol is a sustainable source of liquid fuels and one of the most useful organic chemicals. To date, most of the work in this area has focused on the direct hydrogenation of CO2 to methanol. However, this process requires high operating temperatures (200-250 °C), which limits the theoretical yield of methanol. Thus, it is desirable to find a new strategy for the efficient conversion of CO2 to methanol at relatively low reaction temperatures. This Minireview seeks to outline the recent advances on the indirect hydrogenation of CO2 to methanol. Much emphasis is placed on discussing specific systems, including hydrogenation of CO2 derivatives (organic carbonates, carbamates, formates, cyclic carbonates, etc.) and cascade reactions, with the aim of critically highlighting both the achievements and remaining challenges associated with this field.

Black TiO2 obtained by hydrogenation has attracted enormous attention due to its unusual photocatalytic activity. In this contribution, a novel photocatalyst containing both a titanate–anatase heterostructure and a surface disordered shell was in situ synthesized by using a one-step hydrogenation treatment of titanate nanowires at ambient pressure, which exhibited remarkably improved photocatalytic activity for water splitting under simulated solar light. The as-hydrogenated catalyst with a heterostructure and a surface disordered shell displayed a high hydrogen production rate of 216.5 μmol·h–1, which is ∼20 times higher than the Pt-loaded titanate nanowires lacking of such unique structure. The in situ-generated heterostructure and hydrogenation-induced surface disorder can efficiently promote the separation and transfer of photoexcited electron–hole pairs, inhibiting the fast recombination of the generated charge carriers. A general synergistic effect of the heterostructure and the surface disordered shell on photocatalytic water splitting is revealed for the first time in this work, and the as-proposed photocatalyst design and preparation strategy could be widely extended to other composite photocatalytic systems used for solar energy conversion.

Abstract Highly active and durable bifunctional oxygen electrocatalysts are of pivotal importance for clean and renewable energy conversion devices, but the lack of earth‐abundant electrocatalysts to improve the intrinsic sluggish kinetic process of oxygen reduction/evolution reactions (ORR/OER) is still a challenge. Fe‐N‐C catalysts with abundant natural merits are considered as promising alternatives to noble‐based catalysts, yet further improvements are urgently needed because of their poor stability and unclear catalytic mechanism. Here, an atomic‐level Fe‐N‐C electrocatalyst coupled with low crystalline Fe 3 C‐Fe nanocomposite in 3D carbon matrix (Fe‐SAs/Fe 3 C‐Fe@NC) is fabricated by a facile and scalable method. Versus atomically FeN x species and crystallized Fe 3 C‐Fe nanoparticles, Fe‐SAs/Fe 3 C‐Fe@NC catalyst, abundant in vertical branched carbon nanotubes decorated on intertwined carbon nanofibers, exhibits high electrocatalytic activities and excellent stabilities both in ORR ( E 1/2 , 0.927 V) and OER ( E J=10 , 1.57 V). This performance benefits from the strong synergistic effects of multicomponents and the unique structural advantages. In‐depth X‐ray absorption fine structure analysis and density functional theory calculation further demonstrate that more extra charges derived from modified Fe clusters decisively promote the ORR/OER performance for atomically FeN 4 configurations by enhanced oxygen adsorption energy. These insightful findings inspire new perspectives for the rational design and synthesis of economical–practical bifunctional oxygen electrocatalysts.

Membrane fouling due to superhydropobicity of polytetrafluoroethylene ultrafiltration membranes (PTFE UFMs) represents a grand challenge for their practical applications in diverse water treatment industries. Surface immobilisation of hydrophilic and chemically stable inorganic metal oxides (TiO2, ZrO2, etc) has been developed to improve hydrophilicity of the PTFE UFMs, though they still suffer from expensive and repeating regenerations once fouled. To address such issues, we strive to firmly immobilize g-C3N4 modified TiO2 (g-C3N4/TiO2, hereafter CNTO) onto PTFE UFM via a facile plasma-enhanced surface graft technique using polyacrylic acid (PAA) as a bridging agent. As reported here, the obtained CNTO/PAA/PTFE UFM shows much smaller surface water contact angle (WCA) of 62.3° than that of bare PTFE UFM(115.8°), leading to enhanced water flux of 830 L m−2 h-1 in the initial ultrafiltration of modelled waste-water containing methylene blue (MB). The CNTO/PAA/PTFE UFM is highly resistant to fouling in the prolonged filtration of 1000 mg/L bovine serum albumin (BSA) solution, while the fouled CNTO/PAA/PTFE UFM is able to regenerate rapidly under either UV or visible-light irradiation. The enhanced performance of the novel CNTO/PAA/PTFE UFM is reasonably attributed to its high wettability and robust photocatalytic activity of the g-C3N4/TiO2 coating that follows different self-cleaning mechanisms under UV and visible light irradiations.

The N-methylation of amines with CO2 and H2 is an important step in the synthesis of bioactive compounds and chemical intermediates. The first heterogeneous Au catalyst is reported for this methylation reaction with good to excellent yields. The average turnover frequency (TOF) based on surface Au atoms is 45 h(-1) , which is the highest TOF value ever reported for the methylation of aniline with CO2 and H2 . Furthermore, the catalyst is tolerant toward a variety of amines, which includes aromatic, aliphatic, secondary, and primary amines. Preliminary mechanistic studies suggest that the N-alkyl formamide might be an intermediate in the N-methylation of amine process. Moreover, through a one-pot process, it is possible to convert primary amines, aldehydes, and CO2 into unsymmetrical tertiary amines with H2 as a reductant in the presence of the Au catalyst.

Abstract In situ tuning of the electronic structure of active sites is a long-standing challenge. Herein, we propose a strategy by controlling the hydrogen spillover distance to in situ tune the electronic structure. The strategy is demonstrated to be feasible with the assistance of CoO x /Al 2 O 3 /Pt catalysts prepared by atomic layer deposition in which CoO x and Pt nanoparticles are separated by hollow Al 2 O 3 nanotubes. The strength of hydrogen spillover from Pt to CoO x can be precisely tailored by varying the Al 2 O 3 thickness. Using CoO x /Al 2 O 3 catalyzed styrene epoxidation as an example, the CoO x /Al 2 O 3 /Pt with 7 nm Al 2 O 3 layer exhibits greatly enhanced selectivity (from 74.3% to 94.8%) when H 2 is added. The enhanced selectivity is attributed to the introduction of controllable hydrogen spillover, resulting in the reduction of CoO x during the reaction. Our method is also effective for the epoxidation of styrene derivatives. We anticipate this method is a general strategy for other reactions.

Abstract The electrochemical reduction reaction of carbon dioxide (CO2RR) to carbon monoxide (CO) is the basis for the further synthesis of more complex carbon‐based fuels or attractive feedstock. Single‐atom catalysts have unique electronic and geometric structures with respect to their bulk counterparts, thus exhibiting unexpected catalytic activities. A nitrogen‐anchored Zn single‐atom catalyst is presented for CO formation from CO2RR with high catalytic activity (onset overpotential down to 24 mV), high selectivity (Faradaic efficiency for CO (FE CO ) up to 95 % at −0.43 V), remarkable durability (&gt;75 h without decay of FE CO ), and large turnover frequency (TOF, up to 9969 h −1 ). Further experimental and DFT results indicate that the four‐nitrogen‐anchored Zn single atom (Zn‐N 4 ) is the main active site for CO2RR with low free energy barrier for the formation of *COOH as the rate‐limiting step.

The key challenge for controlling low concentration volatile organic compounds (VOCs) is to develop technology capable of operating under mild conditions in a cost-effective manner. Meanwhile, ozone (O3) is another dangerous air pollutant and byproducts of many emerging air quality control technologies, such as plasma and electrostatic precipitators. To address these multiple challenges, we report here a design strategy capable of achieving the following trifunctions (i.e., efficiently VOCs adsorption enrichment, ozone destruction, and stable VOCs degradation) from the synergistic effect of adsorption center encapsulation and catalytic active sites optimization using 2D manganese(II) monoxide nanosheets decorated carbon spheres with hierarchical core–shell structure. Carbonous residues in the as-synthesized MnOx matrices played a key role for in situ generating homogeneous dispersed unsaturated MnO during the annealing of the as-synthesized C@MnOx in the flow of argon under a proper calcination temperature (550 °C). The formation of the intimacy interface between MnO and carbon not only facilitates the adsorption and subsequent catalytic reaction but also results in a gatekeeper effect on the protection of the carbon sphere against the etching of O3. Such a composite architecture achieved the highest stable removal efficiency (100% for 60 ppm of formaldehyde and 180 ppm of O3 simultaneously) and 100% CO2 selectivity under a GHSV of 60000 mL h–1 g–1. These findings thus open up a way to address current multiple challenges in air quality control using a single hierarchical core–shell structure.

Catalytic oxidation is an effective way to eliminate soot pollution emitted from diesel engines. However, the origination and specific location of active oxygen species are still unclear over noble metal catalysts because of the complex gas (oxygen)–solid (catalyst)–solid (reactant) reaction systems. Herein, we report the high catalytic performance of the nanoflower-like hydrotalcite-derived CoAlO-supported Ag catalyst synthesized by a facile hydrothermal method for soot combustion. Our characterization results demonstrate that metallic Ag nanoparticles (NPs) are highly dispersed on the CoAlO support because of their interactions through electron donation from Co to Ag species. The isotopic 18O2 adsorption/desorption results reveal that gaseous oxygen is readily adsorbed and dissociated on these electron-enriched Ag NPs rather than oxygen vacancies of the CoAlO support. From the 18O2 isothermal soot oxidation results, we newly discover that surface oxygen species adsorbed on Ag sites directly participate in soot oxidation, while those on the CoAlO support only play a negligible role. The kinetic results show that the strengthened Ag–CoAlO interactions can promote not only the quantity but also the intrinsic activity of oxygen species on Ag sites for soot combustion. In addition, the nanoflower-like morphology of the catalyst can greatly improve the soot–catalyst contact efficiency to further enhance the catalytic performance. Our work brings an insight into the identification of oxygen activation/oxidation sites involved in soot oxidation over Ag catalysts supported on hydrotalcite-derived CoAlO metal oxides by systematic isotopic and kinetic investigations, which is beneficial to the rational design of other related catalytic systems.

Many oxyanion-forming metals (As, Sb, Se, Tc, etc.) can be removed from water by adsorption and/or redox reactions involving iron oxides, including the oxides associated with zerovalent iron (ZVI). The rate of antimonite (Sb(III) hydrolysis species) removal by ZVI was determined in open, well-mixed batch reactors as a function of experimental factors, including aging of the ZVI, addition of Fe(II), Sb dose, mixing rate, pH, initial concentrations of Sb(III), etc. However, the largest effect observed was the roughly 6–8 fold increase in Sb(III) removal rate due to the application of a weak magnetic field (WMF) during the experiments. The WMF effect on Sb removal arises from stimulated corrosion and delayed passivation of the ZVI, as evidenced by time series correlation analysis of “geochemical” properties (DO, Fetot, Eh, and pH) measured synchronously in each experiment. The removal of Sb under the conditions of this study was mainly due to oxidation of Sb(III) to Sb(V) and adsorption and coprecipitation onto the iron oxides formed from accelerated corrosion of ZVI, as evidenced by Sb K-edge XANES, EXAFS, and XPS. The degree of the WMF enhancement for Sb(III) was found to be similar to the WMF effect reported previously for Sb(V), As(III), As(V), and Se(VI).

Metal-N-C is a type of attractive electrocatalyst for efficient CO2 reduction to CO. Because of the ambiguity in their atomic structures, the active sites and catalytic mechanisms of the catalysts have remained under debate. Here, the effects of N and C hybrid coordination on the activity of Ni-N-C catalysts were investigated, combining theoretical and experimental methods. The theoretical calculations revealed that N and C hybrid coordination greatly enhanced the capability of single-atom Ni active sites to provide electrons to reactant molecules and strengthens the bonding of Ni to N and C in the Ni-N-C complexes. During the reaction process, the C and N coordination synergistically optimized the reaction energies in the conversion of CO2 to CO. A good agreement between theoretical calculations and electrochemical experiments was achieved based on the newly developed Ni-N-C electrocatalysts. The activity of hybrid-coordination NiN2 C2 was more than double that of single-coordination NiN4 .

Abstract Maximizing the platinum utilization in electrocatalysts toward oxygen reduction reaction (ORR) is very desirable for large‐scale sustainable application of Pt in energy systems. A cost‐effective carbon‐supported carbon‐defect‐anchored platinum single‐atom electrocatalysts (Pt 1 /C) with remarkable ORR performance is reported. An acidic H 2 /O 2 single cell with Pt 1 /C as cathode delivers a maximum power density of 520 mW cm −2 at 80 °C, corresponding to a superhigh platinum utilization of 0.09 g Pt kW −1 . Further physical characterization and density functional theory computations reveal that single Pt atoms anchored stably by four carbon atoms in carbon divacancies (Pt‐C 4 ) are the main active centers for the observed high ORR performance.

Direct selective oxidation of light alkanes, such as ethane, into value-added chemical products under mild reaction conditions remains a challenge in both industry and academia. Herein, the iridium cluster and atomically dispersed iridium catalysts have been successfully fabricated using nanodiamond as support. The obtained iridium cluster catalyst shows remarkable performance for selective oxidation of ethane under oxygen at 100 °C, with an initial activity as high as 7.5 mol/mol/h and a selectivity to acetic acid higher than 70% after five in situ recycles. The presence of CO in the reaction feed is pivotal for the excellent reaction performance. On the basis of X-ray photoelectron spectroscopy (XPS) analysis, the critical role of CO was revealed, which is to maintain the metallic state of reactive Ir species during the oxidation cycles.

A facile two-step strategy was used to prepare black of hydrogenated/nitrogen-doped TiO2 nanoplates (NHTA) with a flower-like hierarchical architecture. In situ nitriding and self-assembly was realized by hydrothermal synthesis using tripolycyanamide as a N source and as a structure-directing agent. After thorough characterization, it was found that the hydrogenation treatment did not damage the flower-like architecture but distorted the anatase crystal structure and significantly changed the band structure of NHTA owing to the increased concentration of oxygen vacancies, hydroxyl groups, and Ti3+ cations. Under AM 1.5 illumination, the photocatalytic H2 evolution rate on the black NHTA was approximately 1500 μmol g-1 h-1 , which was much better than the N-doped TiO2 nanoplates (≈690 μmol g-1 h-1 ). This improvement in the hydrogen evolution rate was attributed to a reduced bandgap, enhanced separation of the photogenerated charge carriers, and an increase in the surface-active sites.

A “three birds one stone” strategy for preparing 1D N-doped porous carbon nanotubes embedded with Co@CoO_x nanoparticles results in the unprecedentedly high-rate Zn–air batteries.

SnO2 has been recognized as excellent catalyst towards formate production from electrochemical CO2 reduction (CO2R). However, it is a great challenge to prepare SnO2 that is stable under the working condition of CO2R and the active center of the SnO2-based catalyst towards CO2R has been illusive. In this work, Sn-In alloy nanoparticles display an InSn4 intermetallic core and an amorphous In-doped tin oxide shell and a CO2-to-formate faradaic efficiency of 94% and a current density of 236 mA cm−2 was achieved at −0.98 V. Operando X-ray absorption and Raman spectroscopy reveal that the In-doped tin oxide shell remains stable under CO2R condition. Density functional theory calculations indicate that the In-doped tin oxide results in the formation of oxygen vacancy, stabilized tin oxide shell and exergonic pathway for CO2-to-formate, which might account for the high performance of the catalysts towards CO2R.