Material Engineering Strategies for Efficient Hydrogen Evolution Reaction Catalysts.

Water electrolysis, a key enabler of hydrogen energy production, presents significant potential as a strategy for achieving net-zero emissions. However, the widespread deployment of water electrolysis is currently limited by the high-cost and scarce noble metal electrocatalysts in hydrogen evolution reaction (HER). Given this challenge, design and synthesis of cost-effective and high-performance alternative catalysts have become a research focus, which necessitates insightful understandings of HER fundamentals and material engineering strategies. Distinct from typical reviews that concentrate only on the summary of recent catalyst materials, this review article shifts focus to material engineering strategies for developing efficient HER catalysts. In-depth analysis of key material design approaches for HER catalysts, such as doping, vacancy defect creation, phase engineering, and metal-support engineering, are illustrated along with typical research cases. A special emphasis is placed on designing noble metal-free catalysts with a brief discussion on recent advancements in electrocatalytic water-splitting technology. The article also delves into important descriptors, reliable evaluation parameters and characterization techniques, aiming to link the fundamental mechanisms of HER with its catalytic performance. In conclusion, it explores future trends in HER catalysts by integrating theoretical, experimental and industrial perspectives, while acknowledging the challenges that remain.

Co/SiO2 Catalyst for Methoxycarbonylation of Acetylene: On Catalytic Performance and Active Species.

Reppe carbonylation of acetylene is an atom-economic and non-petroleum approach to synthesize acrylic acid and acrylate esters, which are key intermediates in the textile, leather finishing, and polymer industries. In the present work, a noble metal-free Co@SiO2 catalyst was prepared and evaluated in the methoxycarbonylation reaction of acetylene. It was discovered that pretreatment of the catalyst by different reductants (i.e., C2H2, CO, H2, and syngas) greatly improved the catalytic activity, of which Co/SiO2-H2 demonstrated the best performance under conditions of 160 °C, 0.05 MPa C2H2, 4 MPa CO, and 1 h, affording a production rate of 4.38 gMA+MP gcat-1 h-1 for methyl acrylate (MA) and methyl propionate (MP) and 0.91 gDMS gcat-1 h-1 for dimethyl succinate (DMS), respectively. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and diffuse reflectance infrared Fourier transform spectra of CO adsorption (CO-DRIFTS) measurements revealed that an H2 reduction decreased the size of the Co nanoparticles and promoted the formation of hollow architectures, leading to an increase in the metal surface area and CO adsorption on the catalyst. The hot filtration experiment confirmed that Co2(CO)8 was generated in situ during the reaction or at the pre-activation stage, which served as the genuine active species. Our work provides a facile and convenient approach to the in situ synthetization of Co2(CO)8 for a Reppe carbonylation reaction.

Noble Metal-Free Light-Driven Hydrogen Evolution Catalysis in Polyampholytic Hydrogel Networks.

Future technologies to harness solar energy and to convert this into chemical energy strongly rely on straightforward approaches to prepare versatile soft matter scaffolds for the immobilization of catalysts and sensitizers in a defined environment. In addition, particularly for light-driven hydrogen evolution, a transition to noble metal-free photosensitizers and catalysts is urgently required. Herein, we report a fully organic light-harvesting soft matter network based on a polyampholyte hydrogel where both photosensitizer (a perylene monoimide derivative) and a H2 evolution catalyst ([Mo3S13]2-) are electrostatically incorporated. The resulting material exhibits sustained visible-light-driven H2 evolution in aqueous ascorbic acid solution, even at rather low loadings of photosensitizer (0.4%) and catalyst (120 ppm). In addition, we provide initial insights into the long-term stability of the hybrid hydrogel. We believe that these results pave the way for a generalized route toward the incorporation of noble metal-free light-driven catalysis in soft matter networks.

Noble-Metal-Free High-Entropy Alloy Nanoparticles for Efficient Solar-Driven Photocatalytic CO2 Reduction.

Metal nanoparticle (NP) cocatalysts are widely investigated for their ability to enhance the performance of photocatalytic materials; however, their practical application is often limited by the inherent instability under light irradiation. This challenge has catalyzed interest in exploring high-entropy alloys (HEAs), which, with their increased entropy and lower Gibbs free energy, provide superior stability. In this study, 3.5 nm-sized noble-metal-free NPs composed of a FeCoNiCuMn HEA are successfully synthesized. With theoretic calculation and experiments, the electronic structure of HEA in augmenting the catalytic CO2 reduction has been uncovered, including the individual roles of each element and the collective synergistic effects. Then, their photocatalytic CO2 reduction capabilities are investigated when immobilized on TiO2. HEA NPs significantly enhance the CO2 photoreduction, achieving a 23-fold increase over pristine TiO2, with CO and CH4 production rates of 235.2 and 19.9 µmol g-1 h-1, respectively. Meanwhile, HEA NPs show excellent stability under simulated solar irradiation, as well high-energy X-ray irradiation. This research emphasizes the promising role of HEA NPs, composed of earth-abundant elements, in revolutionizing the field of photocatalysis.

A binary dumbbell visible light driven photocatalyst for simultaneous hydrogen production with the selective oxidation of benzyl alcohol to benzaldehyde.

Photocatalytic H2 production with selective oxidation of organic moieties in an aqueous medium is a fascinating research area. However, the rational design of photocatalysts and their photocatalytic performance are still inadequate. In this work, we efficiently synthesized the MoS2 tipped CdS nanowires (NWs) photocatalyst using soft templates via the two-step hydrothermal method for efficient H2 production with selective oxidation of benzyl alcohol (BO) under visible light illumination. The optimized MoS2 tipped CdS NWs (20 % MoS2) photocatalyst exhibits the highest photocatalytic H2 production efficiency of 13.55 mmol g-1 h-1 with 99 % selective oxidation of BO, which was 42.34 and 2.21 times greater photocatalytic performance than that of pristine CdS NWs and MoS2/CdS NWs, respectively. The directional loading of MoS2 at the tips of CdS NWs (as compared to nondirectional MoS2 at CdS NWs) is the key factor towards superior H2 production with 99 % selective oxidation of BO and has an inhibitory effect on the photo corrosion of pristine CdS NWs. Therefore, the amazing enhancement in the photocatalytic performance and selectivity of optimized MoS2 tipped CdS NWs (20 % MoS2) photocatalyst is due to the spatial separation of their photoexcited charge carriers through the Schottky junction. Moreover, the unique structure of the MoS2 flower at the tip of 1D CdS NWs offers separate active sites for adsorption and surface reactions such as H2 production at the MoS2 flower (confirmed by Pt photo deposition) and subsequently the selective oxidation of BO at the stem of CdS NWs. This rational design of a photocatalyst could be an inspiring work for the further development of an efficient photocatalytic system for H2 production with selective oxidation of BO (a strategy of mashing two potatoes with one fork).

Scalable One-Pot Fabrication of Carbon-Nanofiber-Supported Noble-Metal-Free Nanocrystals for Synergetic-Dependent Green Hydrogen Production: Unraveling Electrolyte and Support Effects.

Electrocatalytic hydrogen evolution reactions (HER) are envisaged as the most promising sustainable approach for green hydrogen production. However, the considerably high cost often associated with such reactions, particularly upon scale-up, poses a daunting challenge. Herein, a facile, effective, and environmentally benign one-pot scalable approach is developed to fabricate MnM (M═Co, Cu, Ni, and Fe) nanocrystals supported over in situ formed carbon nanofibers (MnM/C) as efficient noble-metal-free electrocatalysts for HER. The formation of carbon nanofibers entails impregnating cellulose in an aqueous solution of metal precursors, followed by annealing the mixture at 550 °C. During the impregnation process, cellulose acts as a reactor for inducing the in situ reductions of MnM salts with the assistance of ether and hydroxyl groups to drive the mass production (several grams) of ultralong (5 ± 1 µM) carbon nanofibers ornamented with MnM nanoparticles (10-14 nm in size) at an average loading of 2.87 wt %. For better electrocatalytic HER benchmarking, the fabricated catalysts were tested over different working electrodes, i.e., carbon paper, carbon foam, and glassy carbon, in the presence of different electrolytes. All the fabricated MnM/C catalysts have demonstrated an appealing synergetic-effect-dependent HER activity, with MnCo/C exhibiting the best performance over carbon foam, close to that of the state-of-the-art commercial Pt/C (10 wt % Pt), with an overpotential of 11 mV at 10 mA cm-2, a hydrogen production rate of 2448 mol g-1 h-1, and a prolonged stability of 2 weeks. The HER performance attained by MnCo/C nanofibers is among the highest reported for Pt-free electrocatalysts, thanks to the mutual alloying effect, higher synergism, large surface area, and active interfacial interactions over the nanofibers. The presented findings underline the potential of our approach for the large-scale production of cost-effective electrocatalysts for practical HER.

Engineering Metallic Alloy Electrode for Robust and Active Water Electrocatalysis with Large Current Density Exceeding 2000 mA cm-2.

The amelioration of brilliantly effective electrocatalysts working at high current density for the oxygen evolution reaction (OER) is imperative for cost-efficient electrochemical hydrogen production. Yet, the kinetically sluggish and unstable catalysts remain elusive to large-scale hydrogen (H2) generation for industrial applications. Herein, a new strategy is demonstrated to significantly enhance the intrinsic activity of Ni1-xFex nanochain arrays through a trace proportion of heteroatom phosphorus doping that permits robust water splitting at an extremely large current density of 1000 and 2000 mA cm-2 for 760 h. The in situ formation of Ni2P and Ni5P4 on Ni1-xFex nanochain arrays surface and hierarchical geometry of the electrode significantly promote the reaction kinetics and OER activity. The OER electrode provides exceptionally low overpotentials of 222 and 327 mV at current densities of 10 and 2000 mA cm-2 in alkaline media, dramatically lower than benchmark IrO2 and is among the most active catalysts yet reported. Remarkably, the alkaline electrolyzer renders a low voltage of 1.75 V at a large current density of 1000 mA cm-2, indicating outperformed overall water splitting. The electrochemical fingerprints demonstrate vital progress toward large-scale H2 production for industrial water electrolysis.

Engineering advanced noble-metal-free electrocatalysts for energy-saving hydrogen production from alkaline water via urea electrolysis.

When the anodic oxygen evolution reaction (OER) of water splitting is replaced by the urea oxidation reaction (UOR), the electrolyzer can fulfill hydrogen generation in an energy-economic manner for urea electrolysis as well as sewage purification. However, owing to the sluggish kinetics from a six-electron process for UOR, it is in great demand to design and fabricate high-performance and affordable electrocatalysts. Over the past years, numerous non-precious materials (especially nickel-involved samples) have offered huge potential as catalysts for urea electrolysis under alkaline conditions, even in comparison with frequently used noble-metal ones. In this review, recent efforts and progress in these high-efficiency noble-metal-free electrocatalysts are comprehensively summarized. The fundamentals and principles of UOR are first described, followed by highlighting UOR mechanism progress, and then some discussion about density functional theory (DFT) calculations and operando investigations is given to disclose the real reaction mechanism. Afterward, aiming to improve or optimize UOR electrocatalytic properties, various noble-metal-free catalytic materials are introduced in detail and classified into different classes, highlighting the underlying activity-structure relationships. Furthermore, new design trends are also discussed, including targetedly designing nanostructured materials, manipulating anodic products, combining theory and in situ experiments, and constructing bifunctional catalysts. Ultimately, we point out the outlook and explore the possible future opportunities by analyzing the remaining challenges in this booming field.

Hollow Plasmonic P-Metal-N S-Scheme Heterojunction Photoreactor with Spatially Separated Dual Cocatalysts toward Artificial Photosynthesis.

Semiconductor-based step-scheme (S-scheme) heterojunctions possess many merits toward mimicking natural photosynthesis. However, their applications for solar-to-chemical energy conversion are hindered by inefficient charge utilization and unsatisfactory surface reactivity. Herein, two synergistic protocols are demonstrated to overcome these limitations based on the construction of a hollow plasmonic p-metal-n S-scheme heterojunction photoreactor with spatially separated dual noble-metal-free cocatalysts. On one side, plasmonic Au, inserted into the heterointerfaces of CuS@ZnIn2 S4 core-shell nanoboxes, not only accelerates the transfer and recombination of useless charges, enabling a more thorough separation of useful ones for CO2 reduction and H2 O oxidation but also generates hot electrons and holes, respectively injects them into ZnIn2 S4 and CuS, further increasing the number of active carriers participating in redox reactions. On the other side, Fe(OH)x and Ti3 C2 cocatalysts, separately located on the CuS and ZnIn2 S4 surface, enrich the redox sites, adjust the reduction potential and pathway for selective CO2 -to-CH4 transformation, and balance the transfer and consumption of photocarriers. As expected, significantly enhanced activity and selectivity in CH4 production are achieved by the smart design along with nearly stoichiometric ratios of reduction and oxidation products. This study paves the way for optimizing artificial photosynthetic systems via rational interfacial channel introduction and surface cocatalyst modification.

Co-Co Dinuclear Active Sites Dispersed on Zirconium-doped Heterostructured Co9 S8 /Co3 O4 for High-current-density and Durable Acidic Oxygen Evolution.

Developing cost-effective and sustainable acidic water oxidation catalysts requires significant advances in material design and in-depth mechanism understanding for proton exchange membrane water electrolysis. Herein, we developed a single atom regulatory strategy to construct Co-Co dinuclear active sites (DASs) catalysts that atomically dispersed zirconium doped Co9 S8 /Co3 O4 heterostructure. The X-ray absorption fine structure elucidated the incorporation of Zr greatly facilitated the generation of Co-Co DASs layer with stretching of cobalt oxygen bond and S-Co-O heterogeneous grain boundaries interfaces, engineering attractive activity of significantly reduced overpotential of 75 mV at 10 mA cm-2 , a breakthrough of 500 mA cm-2 high current density, and water splitting stability of 500 hours in acid, making it one of the best-performing acid-stable OER non-noble metal materials. The optimized catalyst with interatomic Co-Co distance (ca. 2.80 Å) followed oxo-oxo coupling mechanism that involved obvious oxygen bridges on dinuclear Co sites (1,090 cm-1 ), confirmed by in situ SR-FTIR, XAFS and theoretical simulations. Furthermore, a major breakthrough of 120,000 mA g-1 high mass current density using the first reported noble metal-free cobalt anode catalyst of Co-Co DASs/ZCC in PEM-WE at 2.14 V was recorded.

In situ formed nickel tungsten oxide amorphous layer on metal-organic framework derived ZnxNi1-xWO4 surface by self-reconstruction for acid hydrogen evolution reaction.

Noble metal free electrocatalysts for hydrogen evolution reaction (HER) in acid play an important role in proton exchange membrane-based electrolysis. Here, we develop an in situ surface self-reconstruction strategy to construct excellent acidic HER catalysts. Firstly, free-standing zinc nickel tungstate nanosheets inlaid with nickel tungsten alloy nanoparticles were synthesized on carbon cloth as pre-catalyst via metal-organic framework derived method. Amorphous nickel tungsten oxide (Ni-W-O) layer is in situ formed on surface of nanosheet as actual HER active site with the dissolution of NiW alloy nanoparticles and the leaching of cations. While the morphology of the free-standing structure remains the same, keeping the maximized exposure of active sites and serving as the electron transportation framework. As a result, benefiting from disordered arrangement of atoms and the synergistic effect between Ni and W atoms, the amorphous Ni-W-O layer exhibits an excellent acidic HER activity with only an overpotential of 46 mV to drive a current density of 10 mA cm-2 and a quite good Tafel slope of 36.4 mV dec-1 as well as an excellent durability. This work enlightens the exploration of surface evolution of catalysts during HER in acidic solution and employs it as a strategy for designing acidic HER catalysts.

Investigation of Highly Active Carbon-, Cobalt-, and Noble Metal-Free MnO2/NiO/Ni-Based Bifunctional Air Electrodes for Metal-Air Batteries with an Alkaline Electrolyte.

Compared to other battery technologies, metal-air batteries offer high specific capacities because the active material at the cathode side is supplied by ambient atmosphere. To secure and further extend this advantage, the development of highly active and stable bifunctional air electrodes is currently the main challenge that needs to be resolved. Herein, a highly active carbon-, cobalt-, and noble-metal-free MnO2/NiO-based bifunctional air electrode is presented for metal-air batteries in alkaline electrolytes. Notably, while electrodes without MnO2 reveal stable current densities over 100 cyclic voltammetry cycles, MnO2 containing samples show a superior initial activity and an elevated open circuit potential. Along this line, the partial substitution of MnO2 by NiO drastically increases the cycling stability of the electrode. X-ray diffractograms, scanning electron microscopy images, and energy-dispersive X-ray spectra are obtained before and after cycling to investigate structural changes of the hot-pressed electrodes. XRD results suggest that MnO2 is dissolved or transformed into an amorphous phase during cycling. Furthermore, SEM micrographs show that the porous structure of a MnO2 and NiO containing electrode is not maintained during cycling.

Noble-metal-free Co-N-C catalyst derived from cellulose-based poly(ionic liquid)s for highly efficient oxygen reduction reaction.

Noble-Metal-Free nitrogen-doped carbon-based materials are promising electrocatalysts for oxygen reduction reaction (ORR), yet it remains a great challenge to construct efficient porous non-noble metal nitrogen-doped carbon (M-N-C) catalysts with uniform distribution, due to the easy aggregation of metals. Herein, we reported the synthesis and assessment of a novel and efficient noble-metal-free catalyst for oxygen reduction reaction (ORR) from pyrolysis of a cobalt-containing cellulosic poly(ionic liquid) (Co-N-C). The prepared Co-N-C catalyst possesses high surface area, hierarchical porous structure, well-dispersed Co nanoparticles and large amounts of low-coordinated Co active sites. Especially, the Co-N-C-850 sample exhibits a high ORR activity (Eonset = 0.827 V, E1/2 = 0.74 V) that can rival 20 wt% commercial Pt/C (Eonset = 0.833 V, E1/2 = 0.71 V) in alkaline media. Moreover, the Co-N-C-850 sample also shows excellent anti-methanol poisoning activity and long-term stability toward ORR compared with commercial Pt/C. Our study provides a promising avenue both for the development of non-noble M-N-C catalysts for fuel cells and the functional utilization of cellulose.

Thermocatalytic Conversion of CO2 to Valuable Products Activated by Noble-Metal-Free Metal-Organic Frameworks.

Thermocatalysis of CO2 into high valuable products is an efficient and green method for mitigating global warming and other environmental problems, of which Noble-metal-free metal-organic frameworks (MOFs) are one of the most promising heterogeneous catalysts for CO2 thermocatalysis, and many excellent researches have been published. Hence, this review focuses on the valuable products obtained from various CO2 conversion reactions catalyzed by noble-metal-free MOFs, such as cyclic carbonates, oxazolidinones, carboxylic acids, N-phenylformamide, methanol, ethanol, and methane. We classified these published references according to the types of products, and analyzed the methods for improving the catalytic efficiency of MOFs in CO2 reaction. The advantages of using noble-metal-free MOF catalysts for CO2 conversion were also discussed along the text. This review concludes with future perspectives on the challenges to be addressed and potential research directions. We believe that this review will be helpful to readers and attract more scientists to join the topic of CO2 conversion.

Carbonized Polydopamine-Based Nanocomposites: The Effect of Transition Metals on the Oxygen Electrocatalytic Activity.

The electrochemical oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are the most critical processes in renewable energy-related technologies, such as fuel cells, water electrolyzers, and unitized regenerative fuel cells. N-doped carbon composites have been demonstrated to be promising ORR/OER catalyst candidates because of their excellent electrical properties, tunable pore structure, and environmental compatibility. In this study, we prepared porous N-doped carbon nanocomposites (NC) by combining mussel-inspired polydopamine (PDA) chemistry and transition metals using a solvothermal carbonization strategy. The complexation between dopamine catechol groups and transition metal ions (Fe, Ni, Co, Zn, Mn, Cu, and Ti) results in hybrid structures with embedded metal nanoparticles converted to metal-NC composites after the carbonization process. The influence of the transition metals on the structural, morphological, and electrochemical properties was analyzed in detail. Among them, Cu, Co, Mn, and Fe N-doped carbon nanocomposites exhibit efficient catalytic activity and excellent stability toward ORR. This method improves the homogeneous distribution of the catalytically active sites. The metal nanoparticles in reduced (MnO, Fe3C) or metallic (Cu, Co) oxidation states are protected by the N-doped carbon layers, thus further enhancing the ORR performance of the composites. Still, only Co nanocomposite is also effective toward OER with a potential bifunctional gap (ΔE) of 0.867 V. The formation of Co-N active sites during the carbonization process, and the strong coupling between Co nanoparticles and the N-doped carbon layer could promote the formation of defects and the interfacial electron transfer between the catalyst surface, and the reaction intermediates, increasing the bifunctional ORR/OER performance.

Pulsed Light Synthesis of High Entropy Nanocatalysts with Enhanced Catalytic Activity and Prolonged Stability for Oxygen Evolution Reaction.

The ability to synthesize compositionally complex nanostructures rapidly is a key to high-throughput functional materials discovery. In addition to being time-consuming, a majority of conventional materials synthesis processes closely follow thermodynamics equilibria, which limit the discovery of new classes of metastable phases such as high entropy oxides (HEO). Herein, a photonic flash synthesis of HEO nanoparticles at timescales of milliseconds is demonstrated. By leveraging the abrupt heating and cooling cycles induced by a high-power-density xenon pulsed light, mixed transition metal salt precursors undergo rapid chemical transformations. Hence, nanoparticles form within milliseconds with a strong affinity to bind to the carbon substrate. Oxygen evolution reaction (OER) activity measurements of the synthesized nanoparticles demonstrate two orders of magnitude prolonged stability at high current densities, without noticeable decay in performance, compared to commercial IrO2 catalyst. This superior catalytic activity originates from the synergistic effect of different alloying elements mixed at a high entropic state. It is found that Cr addition influences surface activity the most by promoting higher oxidation states, favoring optimal interaction with OER intermediates. The proposed high-throughput method opens new pathways toward developing next-generation functional materials for various electronics, sensing, and environmental applications, in addition to renewable energy conversion.

Boosting CO2 photoreduction by π-π-induced preassembly between a Cu(I) sensitizer and a pyrene-appended Co(II) catalyst.

The design of a highly efficient system for CO2 photoreduction fully based on earth-abundant elements presents a challenge, which may be overcome by installing suitable interactions between photosensitizer and catalyst to expedite the intermolecular electron transfer. Herein, we have designed a pyrene-decorated Cu(I) complex with a rare dual emission behavior, aiming at additional π-interaction with a pyrene-appended Co(II) catalyst for visible light-driven CO2-to-CO conversion. The results of 1H NMR titration, time-resolved fluorescence/absorption spectroscopies, quantum chemical simulations, and photocatalytic experiments clearly demonstrate that the dynamic π-π interaction between sensitizer and catalyst is highly advantageous in photocatalysis by accelerating the intermolecular electron transfer rate up to 6.9 × 105 s-1, thus achieving a notable apparent quantum yield of 19% at 425 nm with near-unity selectivity. While comparable to most earth-abundant molecular systems, this value is over three times of the pyrene-free system (6.0%) and far surpassing the benchmarking Ru(II) tris(bipyridine) (0.3%) and Ir(III) tris(2-phenylpyridine) (1.4%) photosensitizers under parallel conditions.

NiMo-MOF-Derived Carbon-Armored Ni4Mo Alloy of an Interwoven Nanosheet Structure as an Outstanding pH-Universal Catalyst for Hydrogen Evolution Reaction at High Current Densities.

Development of highly efficient and stable non-precious metal-based pH-universal catalysts for hydrogen evolution reaction (HER) at high current densities remains challenging for water electrolysis-based green hydrogen production. Herein, a simple solvothermal process was developed to synthesize a NiMo metal-organic framework (MOF), from which a carbon-armored Ni4Mo alloy of an interwoven nanosheet structure was derived with a two-stage thermal treatment, to serve as a high-performance pH-universal HER catalyst. It requires low overpotentials of 22, 48, and 98 mV to achieve a current density of -10 mA cm-2 and 192, 267, and 360 mV to deliver an ultrahigh current density of -500 mA cm-2 in alkaline, acidic, and neutral media, respectively, and exhibits remarkable operational stability at an ultrahigh initial current density of -500 mA cm-2 for over 50 h, making it promising for applications in large-scale green hydrogen production. The success can be attributed to the unique catalyst design of a carbon-armored, composition-optimized NiMo alloy of an advantageous nanostructure of interwoven nanosheets for enhanced utilization of active sites and mass transfer of electrolytes and gaseous products, made possible with a MOF-derivation fabrication approach.

Fabrication of Noble-Metal-Free Mo2C/CdIn2S4 Heterojunction Composites with Elevated Carrier Separation for Photocatalytic Hydrogen Production.

Molybdenum-based cocatalyst being used to construct heterojunctions for efficient photocatalytic H2 production is a promising research hotspot. In this work, CdIn2S4 was successfully closely supported on bulk Mo2C via the hydrothermal method. Based on their matching band structures, they formed a Type Ⅰ heterojunction after the combination of Mo2C (1.1 eV, -0.27 V, 0.83 V) and CdIn2S4 (2.3 eV, -0.74 V, 1.56 V). A series of characterizations proved that the heterojunction composite had higher charge separation efficiency compared to a single compound. Meanwhile, Mo2C in heterojunction could act as an active site for hydrogen production. The photocatalytic H2 production activity of the heterojunction composites was significantly improved, and the maximum activity was up to 1178.32 µmmol h-1 g-1 for 5Mo2C/CdIn2S4 composites. 5Mo2C/CdIn2S4 heterojunction composites possess excellent durability in three cycles (loss of 6%). Additionally, the mechanism of increased activity for composites was also investigated. This study provides a guide to designing noble-metal-free photocatalyst for highly efficient photocatalytic H2 evolution.

Unveiling the Metal Incorporation Effect of Steady-Active FeP Hydrogen Evolution Nanocatalysts for Water Electrolyzer.

Metal phosphides are promising noble metal-free electrocatalysts for hydrogen evolution reaction (HER), but they usually suffer from inferior stability and thus are far from the device applications. We reported a facile and controllable synthetic method to prepare metal-incorporated M-FeP nanoparticles (M=Cr, Mn, Co, Fe, Ni, Cu, and Mo) with the guide of the density functional theory (DFT). The evaluated HER activity sequence was consistent with the DFT predictions, and cobalt was revealed to be the appropriate dopant. With the optimization of the Co/Fe ratio, the Fe0.67 Co0.33 P/C only required overpotentials of 67 mV and 129 mV to obtain the cathodic current density of 10 and 100 mA cm-2, respectively. It maintained the initial activity in the 10 h stability test, surpassing the other Co-FeP/C catalysts. Ex situ experiments demonstrated that the decreased element leaching and the increased surface phosphide content contributed to the high stability of the Fe0.67 Co0.33 P/C. A proton exchange membrane water electrolyzer was assembled using the Fe0.67 Co0.33 P/C as the cathodic catalyst. It showed a current density of 0.8 A cm-2 at the applied voltage of 2.0 V and retained the initial activity in the 1000 cycles' stability test, suggesting the potential application of the catalysts.