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Developing high-efficiency electrocatalysts for the hydrogen evolution reaction (HER) is of great importance. In this paper, dendrite-free Ni–Cu catalysts were synthesised via one-step pulse electrodeposition under a weak magnetic field (0.5 T). Regardless of the direction of the magnetic field, the ions were affected by the magnetohydrodynamic (MHD) effect, which greatly promoted the mass transfer and dispersion uniformity, and suppressed the uncontrollable agglomeration by electrodeposition. It was found that the nucleation mechanism changed from progressive nucleation under a 0 T magnetic field to instantaneous nucleation under a 0.5 T magnetic field. Large-scale (325 nm, 0 T) dendrite growth on the single-sided plane was successfully suppressed, and replaced by smaller (90 nm, 0.5 T) and uniformly distributed cluster growth around the carbon paper. In addition, the (111) plane was strengthened by the magnetic field. Electrochemical analysis showed that the Ni–Cu catalysts exposed more surface area and exhibited greatly enhanced catalytic activity, which only needed −57.3 mV to deliver the current density of 10 mA cm−2 with a small Tafel slope of 99.4 mV dec−1 in 1 M KOH. Overall, magneto-electrodeposition, especially under weak magnetic field conditions, provides great promise for the preparation of HER catalysts. [ABSTRACT FROM AUTHOR]

High entropy materials (HEM) have been attracting much attention as emerging catalysts for electrochemical water splitting. HEM catalysts have unique properties such as an interesting cocktail effect, broad design space, customizable electronic structure, and excellent entropy stabilization effect compared with single-digit catalysts. This paper provides a comprehensive overview of the use of HEM as a catalyst for hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and water splitting. HEM design strategies including phase structure modulation, defect engineering, electrode configuration engineering, and computational aids are discussed to develop HEM catalysts with high performance and stability. In particular, the importance of density functional theory, high-throughput screening techniques, and machine learning for the discovery and design of HEM catalysts is emphasized. Finally, the challenges and imminent difficulties are prospected, and the corresponding strategies to deal with these challenges are put forward to promote the development of HEM catalysts in the field of electrochemical water splitting. [ABSTRACT FROM AUTHOR]

As a dual-functional catalyst for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), Ru clusters have great potential, but there are certain difficulties regarding their stability on the substrate and the tunability of their electronic environment. Here, the S doped graphited biochar aerogel electrocatalyst was designed and synthesized using terrestrial lignin and algal polysaccharide as a carbon substrate. The Ru clusters were anchored on the S-doped carbon aerogel (P-Ru/SC) by carefully designing the Ru-S bond via a novel plasma assisted high temperature carbonization treatment. The optimized P-Ru/SC-2 catalyst exhibits excellent electrocatalytic performance for the HER and OER, achieving ultra-small overpotentials of 119.6 mV and 193.4 mV at 10 mA cm-2. The dual-electrode requires only 1.47 V to reach 10 mA cm-2. It is worth noting that a large number of S sites on graphited carbon can strongly interact with the Ru clusters, significantly improving the catalytic activity and stability for the HER and OER. [ABSTRACT FROM AUTHOR]

Interfacial engineering emerges as a potent strategy for regulating the catalytic reactivity of metal phosphides. Developing a facile and cost-effective method to construct bifunctional metal phosphides for highly efficient electrochemical overall water splitting remains an essential and challenging issue. Here, a multiphase transition metal phosphide is constructed through the direct phosphorization of a Ni–Co metal–organic framework grown on nickel foam (Ni–Co-MOF/NF), which is prepared by utilizing nickel foam as conductive substrate and nickel source. The resulting transition metal phosphide manifests a pillar-layered morphology, wherein CoP, Ni2P, and Ni5P4 nanoparticles are embedded within each carbon sheet and these carbon sheets assemble into a pillar-shaped structure on the nickel foam (Ni2P–Ni5P4–CoP–C/NF). The heterogeneous Ni2P-Ni5P4–CoP–C/NF with multiple interfaces serves as a highly efficient bifunctional electrocatalyst with overpotentials of −100 mV and 293 mV in the hydrogen evolution reaction and oxygen evolution reaction, respectively, at 50 mA cm−2 in alkaline media. This superior catalytic performance should mainly be ascribed to its enriched active centers and multiphase synergy. When directly applied for alkaline overall water splitting, the Ni2P–Ni5P4–CoP–C/NF couple demonstrates satisfactory activity (1.55 V @10 mA cm−2) along with sustained durability over 18 hours. This method brings fresh enlightenment to the economical and controllable preparation of multi-metal phosphides for energy conversion. [ABSTRACT FROM AUTHOR]

Direct methanol fuel cells (DMFC) are a promising new energy source. However, the lack of high-performance and low-cost methanol oxidation electrocatalysts hinders their commercial application. Firstly, we successfully prepared NENU-5-derived molybdenum carbide material (Cu-MoC) via a co-precipitation and high-temperature carbonization method using a material composed of a copper-based metal–organic skeleton and a molybdenum-based carbide as the main body. Secondly, PtCu nano-alloy catalysts (Pt/Cu-MoC) were prepared using a unique, spontaneous single replacement reaction after metal–organic skeleton (MOF) carbonization. Through the synergistic effect between Pt and Cu and the strong interaction between Mo2C and PtCu, the electronic structure of the Pt is modified, the energy of the d-band center is reduced, electron exchange is accelerated, and catalytic activity is enhanced. Compared with a commercial Pt/C catalyst in alkaline environments, the Pt0.10/Cu-MoC catalyst has a better MOR catalytic activity (563.25 mA mgPt−1), which is 1.5 times higher than that of commercial Pt/C (376.67 mA mgPt−1). The Pt0.10/Cu-MoC catalyst has an onset potential for CO oxidation that is 16 mV lower than that of commercial Pt/C, indicating better resistance to CO poisoning. Exploring carbon materials derived from MOFs with excellent junction support and using them as carriers to prepare Pt-based catalysts is a practical and feasible approach. It provides a way to develop new Pt-based catalysts that perform efficient MOR. [ABSTRACT FROM AUTHOR]

The design of low-cost and high-performance bifunctional catalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) is of great significance for overall water splitting. Herein, RuNi single atom alloy (SAA) decorated on reduced graphene oxide (RuNi@rGO) was synthesized by a facile strategy for use as a bifunctional HER/OER catalyst. The as-obtained RuNi@rGO catalyst exhibits outstanding electrocatalytic activities with an ultralow overpotential for the HER (15 mV) and the OER (240 mV) at a current density of 10 mA cm−2. Density functional theory (DFT) calculations demonstrate that the introduction of Ru single atoms can evidently change the electron distribution and coordination environment around Ni, and reduce the intermediate's adsorption free energy of RuNi@rGO, thus facilitating the HER/OER catalytic rate. Moreover, when used as the cathode and anode of a two-electrode system, the RuNi@rGO-based water splitting device exhibits a low potential of 1.52 V at a current density of 10 mA cm−2, as well as a high faradaic efficiency almost up to 100%, making RuNi@rGO bifunctional electrocatalysts attractive for energy storage and conversion. [ABSTRACT FROM AUTHOR]

The practical application of CO2 electroreduction to CO driven by renewable electricity should simultaneously meet the requirements of low overpotential, high CO faradaic efficiency (FE), and low cost. Herein, a new strategy is reported to construct a porous nanoflower Ni–Al NC catalyst with excellent catalytic activity via p–d orbital hybridization of Al and Ni. The optimized Ni–Al NC catalyst exhibits an outstanding CO2 electroreduction activity with the maximum CO FE of 98%, low onset potential of −0.5 V vs. RHE, and wide FECO plateau (>90% from −0.7 to −1.0 V vs. RHE), showing great promise for practical applications. The experimental results showed that the p–d hybrid Ni–Al NC catalyst not only enriched its reaction sites but also withstood potential changes in the highly selective reduction of CO2 to CO. This study provides a catalyst design strategy for the efficient electrocatalytic reduction of CO2 to CO under varying potentials. [ABSTRACT FROM AUTHOR]

Developing cobalt-based electrocatalysts that can replace precious metals is significant for hydrogen production in water splitting, however, this is still a complex and demanding task. Here, 3D Mo-doped Co3S4 nanosheet arrays are anchored to nickel foam (Mo–Co3S4/NF) through one-step hydrothermal vulcanization of the Co-MOF precursor. The best electrocatalytic performance has been achieved by optimizing the heteroatom content. The Mo–Co3S4-0.1/NF just needs 154 mV at a current density of 10 mA cm−2 for the HER and 320 mV with 50 mA cm−2 for the OER, respectively. Meanwhile, Mo–Co3S4-0.1/NF as both the cathode and anode in an integrated cell only required 1.52 V to create a current density of 10 mA cm−2 without attenuation for 22 h. Doped Mo heteroatoms can optimize the electron configuration and morphology to accelerate the mass charge transfer of Co3S4/NF. This work confirms that the performance of catalytic materials can be enhanced by introducing heteroatoms. [ABSTRACT FROM AUTHOR]

Proton exchange membrane water electrolysis (PEMWE) can be coupled with renewable energy power generation technology and is considered to be a highly promising hydrogen production technology. However, the acidic electrolyte environment, as well as the numerous sulfonic acid groups on the proton exchange membrane surface, can seriously corrode the oxygen evolution reaction (OER) catalyst and even cause deactivation. To develop an efficient acidic OER catalyst, the IrOx/WO3 heterostructure OER catalyst was prepared by a hydrothermal-calcination method. The coordination environment of IrOx was regulated through the electronic rearrangement effect, improving the OER activity and stability of the catalyst in acidic media. The prepared IrOx/WO3 exhibits excellent OER activity in 0.5 M H2SO4, with an overpotential of only 260 mV to achieve a current density of 10 mA cm−2 and a mass activity of 176.8 A gIr−1. It can stably operate for over 12 hours at a current density of j = 10 mA cm−2. [ABSTRACT FROM AUTHOR]

The development of low-cost earth-abundant electrocatalysts to produce ammonia (NH3) with high efficiency for the nitrogen (N2) reduction reaction (NRR) remains challenging. Herein, we propose the development of highly efficient ultrathin nitrogen-vacancy-rich molybdenum nitride nanosheets (MoN-NV) for NRR using basic electrolytes under ambient conditions. In 0.1 M KOH, this catalyst attained a high faradaic efficiency (FE) of ∼14% with an NH3 yield of 22.5 μg h−1 mg−1cat at −0.3 V vs. a reversible hydrogen electrode under ambient conditions. The characterization results and electrochemical studies disclosed that nitrogen vacancies in the MoN-NV nanosheets played a critical role in the enhanced electrocatalytic activity for NRR. Furthermore, the recycling tests confirmed the stability of the catalyst during NRR electrolysis. [ABSTRACT FROM AUTHOR]

Hydrogen (H2) is a new type of renewable energy that can meet people's growing energy needs and is environmentally friendly. In order to improve the industrial application prospects and electrochemical performance of hydrogen evolution catalysts, extensive research on transition metal materials has been carried out. Among the many catalytic materials, cobalt is an element with potential for the hydrogen evolution reaction (HER) due to its abundant reserves, low cost, and small energy barrier for H adsorption. This review classifies the latest research on cobalt-based catalysts according to the types of compound, including cobalt-based sulfides, phosphides, carbides, borides, oxides, etc., and summarizes the latest research progress of cobalt-based compound catalysts in acidic and alkaline media. Strategies to tune the properties of cobalt-based compound catalysts for high catalytic activity for HER are focused on, including structural engineering, defect engineering, and doping, etc. The advantages and limitations of each modified approach are reviewed. Not only that, but also the catalytic activity and advantages of the catalyst are evaluated by using density functional theory (DFT) calculation-related descriptors, activity evaluation parameters, etc. Finally, limitations and challenges of cobalt-based materials for HER are presented, as well as prospects for future research. This paper aims to understand the chemical and physical factors that affect cobalt-based catalysts, and to find directions for future research on cobalt-based catalysts. [ABSTRACT FROM AUTHOR]

The rational design of high-efficiency electrocatalysts for application in water oxidation in alkaline media remains a great challenge. In this paper, Ni3+-rich nanograss-like Mo-doped Ni3S2/NiS/VS arrays grown on nickel foam (denoted as Mo-NiVS@NF) have been successfully constructed through a hydro/solvothermal method. Interestingly, Mo-NiVS@NF exhibits superior catalytic OER performance, needing an overpotential of 217 mV to drive a current density of 10 mA cm−2, outperforming most previously reported NiS-based electrocatalysts. The result indicates that the Ni3+-rich active sites caused by the modulation of the electronic structure environment via the introduction of V and high-valency Mo play an important role in the high activity for the OER. Moreover, this catalyst shows high long-term electrochemical durability. [ABSTRACT FROM AUTHOR]

Heterostructures formed by combining semiconductor materials with different band structures can provide work functions, d-band positions and electronic properties different from bulk materials and are considered as an effective strategy to improve the catalytic activity through electronic modification. In this study, an efficient MoS2/Fe-Ni3S2/NF heterojunction material was prepared by a two-step hydrothermal method. With the help of flake Ni(OH)2 synthesized in the first step, growth sites were provided for flake Ni3S2. The electronic structure of Ni3S2 was optimized by Fe doping, while the construction of the MoS2/Fe-Ni3S2 heterostructure allowed the catalyst to expose more active sites. MoS2/Fe-Ni3S2/NF exhibited a small charge transfer resistance and excellent electrocatalytic performance. At a current density of 10 mA cm−2, only low overpotentials of 148 mV and 118 mV were required for the oxygen precipitation reaction (OER) and hydrogen precipitation reaction (HER), respectively. Notably, when MoS2/Fe-Ni3S2/NF is used as the anode and cathode for overall hydrolysis, only 1.51 V is required to reach a current density of 10 mA cm−2, demonstrating its great potential for application in hydrolysis. This work provides a feasible idea for the rational construction of non-precious metal bifunctional electrocatalysts with excellent performance. [ABSTRACT FROM AUTHOR]

The exploitation of highly active and stable catalysts for reduction of CO2 and water oxidation is one of the approaches to facilitate scalable and sustainable CO2 reduction potentially at the industrial scale. Herein, a feasible strategy to rationally build an overall CO2 + H2O electrocatalytic reaction device is the preparation and matchup of a high-performance CO2 reduction catalyst and low-cost and highly active oxygen anode catalyst. A heterostructured nanosheet, γ-NiOOH/NiCO3/Ni(HCOO)2, exhibited superior catalytic activity in the oxygen evolution reaction, and was integrated with CoPc/Fe–N–C to build an overall CO2 + H2O cell with a current density of 10 mA cm−2 at a very low cell voltage of 1.97 V, and the faradaic deficiency of CO2 to CO was maintained at greater than 90% at 1.9 V. [ABSTRACT FROM AUTHOR]

Zn–N–C catalysts have garnered attention as potential electrocatalysts for the oxygen reduction reaction (ORR). However, their intrinsic limitations, including poor activity and a low density of active sites, continue to hinder their electrocatalytic performance. In this study, we have devised a dual-template strategy for the synthesis of Zn, N, S co-doped nanoporous carbon-based catalysts (Zn–N/S–C(S, Z)) with a substantial specific surface area and a graded pore structure. The introduction of S enhances electron localization around the Zn–Nx active centers, facilitating interactions with oxygen-containing substances. The resulting Zn–N/S–C(S, Z) sample exhibits outstanding performance in an alkaline solution, demonstrating a half-wave potential of 0.89 V. This value surpasses that of commercial Pt/C by 40 mV. Furthermore, when combined with RuO2 (Zn–N/S–C(S, Z) + RuO2), the catalyst demonstrates exceptional performance in a Zn–air battery, offering an open-circuit voltage (OCV) of 1.47 V and a peak power density of 290.8 mW cm−2. This study paves the way for the development of highly dispersed and highly active Zn-metal site catalysts, potentially replacing traditional Pt-based catalysts in various electrochemical devices. [ABSTRACT FROM AUTHOR]

The development of efficient and stable catalysts for the oxygen reduction reaction (ORR) is crucial to enable practical large-scale application of Zn–air batteries (ZABs). This study investigates the utilization of N, S co-doped coal-based activated carbon materials, synthesized through facile reactions, which exhibit high specific surface area and abundant active sites. The results of material characterization and experiments indicate that co-doping with N and S can effectively modify the charge distribution of coal-based activated carbon materials, increase the active sites, and ultimately enhance their performance in the oxygen reduction reaction (ORR). The N, S-AC catalyst exhibits remarkable catalytic activity for the ORR in alkaline electrolytes, demonstrating a high half-wave potential (E1/2 = 0.79 V), ultimate current density (jL = 6.35 mA cm−2) and stability, as well as considerable tolerance to methanol. The N, S-AC-based ZAB also demonstrates exceptional performance, achieving a maximum power density of 142 mW cm−2 and a specific capacity of 804 mA h gZn−1. This study not only simplifies the preparation process for heteroatom-doped coal-based activated carbon catalysts but also explores practical applications for ZABs. [ABSTRACT FROM AUTHOR]

It is widely acknowledged that interface engineering strategies can significantly enhance the activity of catalysts. In this study, we developed a CoMoP nanoarray directly grown in situ on a nickel foam (NF) substrate, with the interface structure formed through the electrodeposition of MnOxHy. The resulting heterostructure MnOxHy/CoMoP/NF exhibited remarkable hydrogen evolution reaction (HER) activity, achieving overpotentials as low as 61 and 138 mV at 10 and 100 mA cm−2, respectively. Moreover, MnOxHy/CoMoP/NF demonstrated efficient oxygen evolution reaction (OER) activity with an overpotential of 330 mV at 100 mA cm−2. Remarkably, MnOxHy/CoMoP/NF maintained its catalytic properties and structural integrity even after working continuously for 20 h facilitating the HER at 10 mA cm−2 and the OER at 100 mA cm−2. The Tafel slopes of the HER and OER were determined to be as small as 14 and 55 mV dec−1, respectively, confirming that the coupled interface conferred fast reaction kinetics on the catalyst. When applied in overall water splitting, MnOxHy/CoMoP/NF delivered a voltage of 1.91 V at 100 mA cm−2 with excellent stability. This study demonstrated the feasibility of utilizing a simple electrodeposition technique to fabricate a heterogeneous structure with bifunctional catalytic activity, establishing a solid foundation for diverse industrial applications. [ABSTRACT FROM AUTHOR]

NiO has been widely studied as a potential Earth-abundant electrocatalyst for the oxygen evolution reaction (OER). Defect engineering and constructing hollow nanostructures are effective methods to improve electrocatalytic performance, so exploring an efficient route to obtain NiO catalysts simultaneously possessing oxygen vacancies and hollow nanostructures is necessary. In this work, core–shell NiO1−x hollow spheres with oxygen vacancies are prepared through a solvothermal strategy followed by thermal treatment under an H2/Ar atmosphere. And the content of oxygen vacancies can be regulated by varying the calcination time. Importantly, the existence of rich oxygen vacancies in NiO and its unique core–shell hollow structure promote water adsorption and enhance charge transfer and thus the core–shell NiO1−x hollow spheres show appealing electrocatalytic performance, demonstrating efficient OER electrocatalysis with an overpotential (η) of 360 mV (at 10 mA cm−2) and Tafel slope of 103.9 mV dec−1 in an alkaline medium. [ABSTRACT FROM AUTHOR]

Powder electrocatalysts for oxygen evolution reactions usually need adhesives for electrocatalytic performance tests, leading to the increase of resistance, reduction of catalyst loading, and easy stripping of the catalyst under long-time or high current operation. In this study, Ce-doped CoFe layered double hydroxides were uniformly grown on nickel foam by a one-step hydrothermal route. A nanostructured self-supported electrode Ce-CoFe-LDH/NF without adhesive was obtained directly, which has a regular nanoneedle morphology with a length of ∼1.2 μm and tip width of ∼20 nm. Adopting Ce3+ ions with a large radius to partially displace Fe3+ ions with a small radius produced lattice distortion and more defects in the host layer of CoFe-LDH, whereby possessing the great potential to enhance catalytic behaviors. Once used as an electrocatalyst for the oxygen evolution reaction, Ce-CoFe-LDH/NF shows an outstanding electrocatalytic performance, including an optimized overpotential of 225 mV at 10 mA cm−2, a decreased Tafel slope of 34.34 mV dec−1, and a low charge transfer impedance of 2.4 Ω in 1 M KOH electrolyte. Moreover, the overpotential of the working electrode increased by only 0.04 V after 24 hours and was maintained at a current density of 50 mA cm−2. These results demonstrate a low-cost strategy compared to using noble metal OER electrocatalysts. Thus, this study highlights a ready universal approach to fabricate high-performance supported catalysts for energy-related applications. [ABSTRACT FROM AUTHOR]

The development and optimization of electrocatalysts is one of the key points to reduce the energy barrier of electrocatalytic water splitting and improve the kinetics of electrocatalytic reactions. It is necessary to develop low-cost, high-performance electrocatalysts with large-scale application prospects. In order to solve this problem, hybrid structured ZnCo2O4@Co3O4 nanowires are successfully synthesized through hydrothermal synthesis and electrodeposition. As electrocatalysts for water splitting, ZnCo2O4@Co3O4 can reach a current density of 50 mA cm−2 at an overpotential of 278 mV for the OER and 166 mV@−10 mA cm−2 for the HER, which could be higher than that of single ZnCo2O4 and Co3O4. At the same time, ZnCo2O4@Co3O4 samples also exhibit a cell voltage of 1.67 V at a high current density of 50 mA cm−2 and superior durability for 50 h. The fabricated product also showcases a specific capacitance of 1316 F g−1 at 1 A g−1. Additionally, the assembled device attains a maximum energy density of 47.3 W h kg−1 at a power density of 1126 W kg−1. Furthermore, density functional theory (DFT) calculation further confirms that the heterostructure can significantly promote Gibbs free energy for hydrogen adsorption. And the significant increase in the density of total states (DOS) also enhances the catalytic activity for the HER. [ABSTRACT FROM AUTHOR]

Solar energy conversion to chemical energy via light-induced H2O splitting to O2 and H2 is considered to be a promising solution to meet the growing global energy demands. To make this transformation economically viable, it is necessary to develop sustainable photocatalytic systems. Herein, we present an efficient photocatalytic H2 production system which relies on components comprised of low-cost and high-abundance elements. In particular, a series of mononuclear complexes [Ni(LNS)3]− and [Ni(N^N)(LNS)2] and a hexanuclear complex [Ni(LNS)2]6 (N^N = diimine and LNS− = heterocyclic thioamidate with different group-substituents) were synthesized and utilized as catalysts, in combination with N-doped carbon dots as photosensitizer, for efficient H2 evolution from aqueous protons. Differences in H2 production efficiency were observed among the studied Ni(II) catalysts, with complexes bearing ligands with stronger electron-donating ability exhibiting higher catalytic activity. A remarkable catalytic efficiency enhancement was observed for the hexanuclear complex, with catalyst loadings lower than those of the mononuclear Ni(II) complexes, affording TONs >1550 (among the highest values reported for photocatalytic systems of similar type operating in H2O). These data provide an indication of catalytic cooperativity between the metal centers of the hexanuclear complex, and demonstrate the crucial role of atomically precise polynuclear Ni(II) catalysts in light-induced H2 production, a result that can guide future catalyst design towards the development of highly efficient, low-cost and environmentally benign photocatalytic systems. [ABSTRACT FROM AUTHOR]

It is still a challenge to develop very effective and stable non-noble catalysts for the hydrogen evolution reaction (HER). Here, a self-supported porous Ni–Mo–Cu coating is prepared by the dynamic hydrogen bubble template (DHBT) method. This three-dimensional (3D) porous Ni–Mo–Cu coating can offer a large surface area, which helps expose more active sites and promote the transmission of electrons and materials. To achieve this, the 3D porous Ni–Mo–Cu coating catalyst requires a low overpotential value of 70 mV at 10 mA cm−2 in 1 M KOH and stable catalytic properties at a high current density of 500 mA cm−2 for more than 10 h with no obvious evidence of degradation. DFT calculations show the source of the excellent catalytic performance of the 3D porous Ni–Mo–Cu catalyst in alkaline media, including the kinetic energy and adsorption energy. This work provides significant insight into the design of efficient 3D porous materials. [ABSTRACT FROM AUTHOR]

Electricity-to-chemical production from a hybrid microbial–inorganic catalytic system relies upon biocompatible and efficient catalysts for hydrogen evolution reactions (HERs). Herein, metal-free nitrogen-doped carbon nanosheets (NC) with no metal leaching and little generation of reactive oxygen species were synthesized to develop an efficient hybrid catalytic system for converting CO2 to poly-β-hydroxybutyrate. A yield of 538 mg L−1 with an electricity-to-organic efficiency of 10.5% was obtained, which outcompetes most of the previous achievements. The coupling of NC with Ralstonia eutropha H16 reduced the HER overpotential by 200 mV. It was attributed to the doped N atoms facilitating the immobilization of bacteria on the catalysts to enhance hydrophilicity. Besides, the [NiFe]-hydrogenase from R. eutropha accelerates the desorption of H2 and may provide an effective HER catalytic center on the catalysts. This study reveals the synergistic interactions between metal-free catalysts and R. eutropha H16 to promote H2 production and CO2 conversion. [ABSTRACT FROM AUTHOR]

The pursuit of hydrogen peroxide (H2O2) production via two-electron electrochemical oxygen reduction reaction (ORR) is hampered by the lack of high-performance electrocatalysts. In this work, a series of single metal (i.e., Fe, Co, Ni, and Cu) atom catalysts anchored into N-doped carbon nanosheets (NCNSs) are evaluated for H2O2 production at pH-universal electrolytes. The catalytic performance of the samples, including current density, H2O2 selectivity, turnover of frequency (TOF), and faradaic efficiency, are characterized by electrochemical measurements. The generation of H2O2 is monitored by a UV-vis spectrophotometer. Among the samples, Cu/NCNSs exhibits the best catalytic performance with a ring current density of 2.15 mA cm−2, TOF of 15.8 s−1 at 0.1 V vs. reversible hydrogen electrode, Tafel slope of 88 mV dec−1, and H2O2 selectivity of 100% at 0.57 V in alkaline media. Importantly, the Cu/NCNSs yields H2O2 selectivity of 81% at 0.05 V in acidic electrolytes. In contrast, Cu nanoparticles possess an inferior current density and much lower H2O2 selectivity via the 4e− ORR pathway. Further quantitative analysis of H2O2 demonstrates that the Cu/NCNSs catalyst has an H2O2 production rate of 5.1 mol gcatalyst−1 L−1 h−1 in alkaline media at 0.4 V, which is larger than those in acidic media (3.2 mol gcatalyst−1 L−1 h−1) and neutral media (2.2 mol gcatalyst−1 L−1 h−1) at −0.2 V. Such performance of Cu/NCNSs renders it as one of the best catalysts for H2O2 production. [ABSTRACT FROM AUTHOR]

Transition-metal-based metal–organic frameworks (MOFs) have received great interest for the development of low cost, platinum-free, non-precious water splitting electrocatalysts for hydrogen generation to resolve the energy crisis. Recent studies are mainly concerned with the use of MOFs as a self-sacrificing template for the synthesis of carbon-based electrocatalysts encapsulating metallic sites. However, the process often produces undesired metal nanoparticles, lowering the catalytic activity of the materials. This report explores a novel strategy to improve the intrinsic electrocatalytic activity of MOFs by a ligand substitution method. Ligands with different electron donating capacity have been used for the substitution process and the hydrogen evolution activity has been found to be greatly affected by the presence of different donor ligands. The MOF used in this work is designed with Ni as a metal center with 5-azido isophthalic acid as the primary linker. Subsequently, the MOF is functionalized with different organic moieties, i.e., N,N-dimethylethylenediamine (DMEDA) and 4-aminotetrafluoropyridine (4-ATFP) with rich non-metal catalytic active sites by means of post synthetic modification. A comparative study has been performed which shows the 4-ATFP functionalized MOF to have the best electrocatalytic activity among the three with significant performance in all three media, i.e. neutral, acidic and alkaline. Furthermore, theoretical approaches have been employed for the analysis of these experimental observations. [ABSTRACT FROM AUTHOR]

Developing highly efficient electrocatalysts is crucially significant for the application of advanced energy conversion. The Fe–N–C single-atom catalyst is promising for CO2 electroreduction reaction (CO2RR) but suffers from insufficient intrinsic activity and inferior conductivity, which could be addressed by redistributing the electron density via heteroatom doping. Herein, we synthesized S-doped Fe–N–C (Fe–SN–C) as an advanced electrocatalyst for CO2RR using a simple trapping–pyrolysis strategy. Density functional theory calculations and experimental results indicate that S doping increases the d-band electrons and conductivity of Fe–SN–C by electron donating, and thus boosts *CO desorption during the CO2RR process and suppresses the competing hydrogen evolution reaction. Consequently, Fe–SN–C exhibits the maximum CO faradaic efficiency of 93% at −0.5 V and the highest partial current density of 10.1 mA cm−2 at −0.8 V for 2e− CO2RR. This finding provides a feasible and controllable method to achieve advanced electrocatalysts for efficient energy conversion. [ABSTRACT FROM AUTHOR]

The tunable electronic structure of the central metal atoms in single-atom catalysts (SACs) helps to control the adsorption energy of reactants and different reaction intermediates involved in multistep chemical processes. Although SACs have been recently proposed to be effective for electrochemical CO2 reduction to C1 products such as HCOOH, CH3OH and CH4, their role in catalysing CO2 reduction to C2 products involving more complex reaction pathways is largely unknown. Herein, by means of systematic first-principles simulations, we thoroughly evaluate a total of 27 transition metal-based SACs supported on a g-C2N monolayer for CO2 reduction to C2 products such as ethene and ethanol. Our results demonstrate that the SACs reveal limiting potential values ranging from −1.50 to −2.70 V and are capable of effectively suppressing the competitive hydrogen evolution reaction. The most effective candidates capable of reducing CO2 to C2 products were found to be Cu@C2N, Cr@C2N, and Fe@C2N exhibiting limiting potential values of −1.50, −2.23, and −2.27 V, respectively. We further find that the catalytic activities of all the SACs can be correlated with the adsorption free energy of one of the intermediate species (*COCH2O) making it a suitable descriptor for evaluating their CO2 reduction activity. Hence, this study provides key inputs regarding CO2 conversion to C2 products on SACs and is expected to lead to further explorations for future design of SACs for the formation of multicarbon products. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) are a new category of polymer with well-defined porous and crystalline properties that consist of lightweight elements. Strong covalent linkages connect these elements. Because of these covalent bonds, these substances have advantages such as adjustable features, low density, and a large surface area. Owing to these fascinating features, these materials reveal a promising kind of porous framework. Since COFs are applicable in various areas of gas separation, catalysis, chemical sensing, and energy storage, these materials appeal to researchers. Materials that benefit from tunable porosity and high surface area could be appropriate and desirable choices as next-generation catalytic substances and provide a wonderful opportunity in the field of catalytic usage. They are suitable for such catalytic activities as hydrogen evolution reactions, CO2-to-CO conversion, and oxygen evolution reactions. There are several approaches to synthesizing COFs, including the solvothermal method, microwave method, sonochemical method, and mechanochemical method. The purpose of this review article is to present the latest and most significant applications of COFs as catalysts. With an emphasis on synthetic approaches, some novel fabricated COFs are also evaluated. [ABSTRACT FROM AUTHOR]

Developing efficient bifunctional hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalysts is beneficial for simplifying the design of electrolytic cells and reducing the cost of device manufacturing. Herein, a metal phosphide nanoarray (NiMo–Fe–P) electrocatalyst was designed by in situ ion exchange and low-temperature phosphating to promote overall water splitting in 1 M KOH. NiMo–Fe–P demonstrates superb HER and OER activities as reflected by the low overpotentials of 73.1 mV and 215.2 mV, respectively, at a current density of 10 mA cm−2. The addition of Fe changes the electronic structure of Ni, which is conducive to the chemisorption of oxygen-containing intermediates and reduces the energy barrier for water decomposition. Besides, the metal phosphide not only acts as the active site of the HER, but also improves the conductivity of the catalyst. Furthermore, nanowire arrays and the small particles generated on their surfaces provide a high electrochemical active surface area (ECSA), which was beneficial for the exposure of active sites. Attributed to these advantages, the cell voltage of the water electrolyzer constructed with NiMo–Fe–P as both the cathode and anode is only 1.526 V at 10 mA cm−2, and it maintains excellent stability for 100 h with near negligible changes in potential. [ABSTRACT FROM AUTHOR]

The rational design of a highly efficient oxygen evolution reaction (OER) is crucial for the practical applications of water electrolysis. Herein, a hybrid Co3O4@FeOOH/NF electrode was fabricated by loading FeOOH sheets on the surface of Co3O4 nanosheet arrays via a newly developed chemical deposition protocol. The decoration of FeOOH on Co3O4 nanosheet arrays not only endows a strong electronic interaction between the two components but also offers sufficient active sites for the OER process. Benefitting from these advantages, Co3O4@FeOOH/NF exhibited outstanding OER activity in terms of a low overpotential of 209 mV at 10 mA cm−2 and a low Tafel slope of 48.9 mV dec−1. Moreover, nearly steady state operation current and negligible change in the phase and morphology of the catalyst also indicate remarkable stability. This work may provide an important guide for the design of high-performance electrocatalysts for energy conversion applications. [ABSTRACT FROM AUTHOR]

Rational design and construction of low-cost overall water splitting catalysts with high efficiency is of great significance to the green chemistry industry. Herein, a CoFeP/NC@CoP/Ni2P heterostructure is constructed via phosphiding CoFe-Prussian blue analogue@NiCo-precursor (CoFe-PBA@NiCo-Pre). This novel synthesis strategy can be used to prepare heterostructures, which significantly promote charge transfer due to a moderately regulated electronic structure and a strongly coupled heterointerface for electrocatalysis. Notably, the as-prepared CoFeP/NC@CoP/Ni2P heterostructure catalyst shows outstanding performances with small overpotentials of 256 mV for the oxygen evolution reaction and 177 mV for the hydrogen evolution reaction at 10 mA cm−2, respectively. Besides, when CoFeP/NC@CoP/Ni2P is used as anode and cathode catalysts, the cell voltage is only 1.66 V at 50 mA cm−2. This work provides a novel perspective for the design and construction of heterostructure electrocatalysts for water splitting. [ABSTRACT FROM AUTHOR]

Construction of molybdenum phosphides (MoP) that are connected to conductive composite materials has been demonstrated to be an effective strategy for improving the activity of MoP, and it is crucial for both the hydrogen evolution reaction (HER) and lithium-ion batteries (LIBs). However, increasing the exposed active sites and simultaneously enhancing the synergistic effect between MoP and the conductive substrate is challenging. Herein, constructing a multi-hierarchical conducting connection based on carbon nanoparticles and reduced graphene oxide (rGO) sheets was proposed. MoP nanoparticles were in situ grown in a carbon matrix to form flower-like MoP/C particles and were well scattered in stable lamellar rGO nanosheets. Benefiting from the conductive network and good dispersion of active sites, the resultant MoP/C-rGO hybrid exhibits efficient HER activity, with Tafel slopes of 69 mV dec−1 and 87 mV dec−1 under acidic and alkaline conditions. Significantly, even when applied as an anode for LIBs, it demonstrates excellent storage performance with a high specific capacity and long-term stability. It displays superior cycle performance of a reversible capacity of 624.6 mA h g−1 at 0.5 A g−1 after 500 cycles. This work provides insight into the construction of multi-hierarchical structures for efficient bifunctional nanostructural electrodes for energy conversion and storage. [ABSTRACT FROM AUTHOR]

The hydrogen evolution reaction (HER) has an important role in H2 production. Two-dimensional metal–organic framework nanosheets (2D MOF NSs) have become durable and efficient electrocatalysts for the HER due to their ultrathin thickness and large surface area, but such nanosheets are usually less conductive and tend to aggregate, which greatly affect their electrocatalytic efficiency. The introduction of carbon nanotubes (CNTs) on the substrate nanosheets may prevent the aggregation of nanosheets, enhance their conductivity and bring the synergistic effect of multilevel nanostructures. Herein, we propose a simple and unique strategy to yield electrocatalysts with multilevel nanostructures, in which CNTs are grown in situ from 2D Ni-MOF NSs through calcination. Ni nanoparticles (NPs) encapsulated at the tips of CNTs can be readily converted into NiSe2 NPs after selenization. The optimized NiSe2-NPs/CNTs/Ni-MOF NS catalyst exhibits an enhanced electrocatalytic HER performance. Furthermore, the two-electrode system that uses NiSe2-NPs/CNTs/Ni-MOF NSs/NF as both the anode and the cathode shows good electrocatalytic activity toward overall water splitting in 1.0 M KOH. This report provides a new insight into the synthesis of CNTs from simple MOFs and multilevel nanostructures composed of metal chalcogenide NPs, CNTs and 2D Ni-MOFs for efficient electrocatalytic HER. [ABSTRACT FROM AUTHOR]

As a narrow bandgap semiconductor, transition metal selenides are promising as excellent electrocatalysts for hydrogen evolution reactions (HERs). Herein, using an ultra-thin MOF as the precursor, a Co-doped core–shell shaped NiSe2 based catalyst is successfully constructed by a two-step calcination method as an efficient HER catalyst. Experiments and theoretical calculations indicate that the introduction of Co adjusts the electronic structure of Ni and Se, promoting charge transfer and reducing the energy barrier of the rate-limiting step to accelerate the hydrogen precipitation reaction. In addition, the core–shell structure contributes to mass transport, and the outer carbon layer improves the stability of the catalyst. The optimal catalyst (Ni0.75Co0.25Se2@NC) exhibited satisfactory electrocatalytic activity as evidenced by a low overpotential of −143 mV at a current density of −10 mA cm−2 and a small Tafel slope of 37.5 mV dec−1. This work provides a valuable strategy for fabricating efficient NiSe2 based electrocatalysts for the HER. [ABSTRACT FROM AUTHOR]

Seeking and designing low-cost and efficient bifunctional electrocatalysts to replace the traditional Pt and IrO2 catalysts is significant for the development of overall water splitting. Herein, the precursor of Mo intercalation into the CoFe-LDH interlayer is prepared by a simple hydrothermal method, and then the cross-linked MoS2/FeCo2S4 nanosheet arrays are deposited on high conductivity carbon cloth by further hydrothermal vulcanization. The prepared MoS2/FeCo2S4/CC catalyst served as a bifunctional electrocatalyst for overall water splitting presenting an excellent electrocatalytic performance with an overpotential of 161 mV for the HER at 10 mA cm−2, and 307 mV for the OER at 50 mA cm−2. The excellent electrochemical performance is attributed to the reasonable design and selection of composite catalysts and the unique morphology of the interconnected nanosheets. [ABSTRACT FROM AUTHOR]

Transition metal phosphides have been widely studied because of their low cost and good conductivity, attempting to replace precious metal-based materials as new electrochemical catalysts for oxygen evolution reaction. However, the existing high-performance phosphide catalysts for oxygen evolution reaction have bottlenecks such as difficulty to accurately determine the components and the catalytic mechanism. Therefore, in this study, we designed and synthesized FeP/CoP heterogeneous materials with a unique porous morphology as OER catalysts. The as-prepared heterogeneous materials have excellent OER catalytic activity and stability. The overpotential at 10 mA cm−2 is only 266 mV, and the Tafel slope is 60.86 mV dec−1. We believe that the good catalytic performance of the as-prepared material is mainly due to the unique morphology and redistribution of interfacial charges. The results of this study provide new ideas for designing efficient metal phosphide-based OER catalysts. [ABSTRACT FROM AUTHOR]

The oxygen evolution reaction (OER) has become the main barrier to electrochemical water splitting, owing to sluggish kinetics. To accelerate the OER process, a nature-abundant non-noble metal catalyst with outstanding catalytic activity is required. Here, a hierarchical CoMoO4@CoFe layered double hydroxide (LDH, denoted by CoMoO4@CoFe/NF) heterostructure supported on three-dimensional (3D) nickel foam (NF) was synthesised by electrodepositing CoFe-LDH nanosheets on the surface of CoMoO4 nanoplates to boost the electrocatalytic performance for the OER. The coupling between CoMoO4 and CoFe-LDH established abundant boundaries, which exposed abundant active sites. Furthermore, the electron transfer in the hierarchical heterostructure effectively promoted the adsorption and dissociation of H2O molecules. Harnessing the aforementioned synergistic effect significantly improved the intrinsic reaction kinetics of the OER. At 10 mA cm−2, CoMoO4@CoFe/NF reached a small overpotential of 245 mV at room temperature and exhibited outstanding stability for at least 47 h. Furthermore, the Tafel slope for CoMoO4@CoFe/NF was only 46 mV dec−1. This study provides new ideas for the rational design of hierarchical structures and the use of interface interactions. [ABSTRACT FROM AUTHOR]

It is of utmost importance to explore bifunctional electrocatalysts for water splitting. Herein, unique ZnCo2O4–CoOOH heterostructured ultrathin nanosheets on Ni foam are reported that combines a two-step hydrothermal method. This catalyst exhibits excellent catalytic performances to achieve a current density of 10 mA cm−2 with an ultralow overpotential of 115 mV for HER, attaining an overpotential of 238 mV at 20 mA cm−2 for OER. Remarkably, ZnCo2O4–CoOOH/Ni shows a voltage of 1.494 V to drive a current density of 10 mA cm−2. Such performances are due to the inter-penetrative pores present in the ultrathin nanosheets that provide large surface areas and expose massive active sites to enhance activities. In addition, the unique nanosheet structure and the 3D Ni foam substrate possess large specific surface areas, which can facilitate mass diffusion. This excellent performance is ascribed to the ZnCo2O4–CoOOH heterostructure that manipulates strong synergy to improve the electrochemical activity. This study offers new insight on an innovative approach for the exploitation of effective bifunctional electrocatalysts with a heterostructure. [ABSTRACT FROM AUTHOR]

The advancement of a bifunctional electrocatalyst consisting of Earth's rich elements and exhibiting high efficiency is the key to obtain hydrogen fuel by overall water splitting (OWS). Here, a facile and extensible hydrothermal synthesis of an electrocatalyst on iron foam (MoOx/Fe1−xS/IF) as a robust bifunctional catalyst with excellent catalytic activity is designed for the hydrogen evolution reaction (HER) with an overpotential of 142 mV at 100 mA cm−2, and for the OER with lower overpotentials of 300 and 500 mV at 100 and 1000 mA cm−2. The good activity is ascribed to the controllable morphology, stronger bonding of the catalyst to a substrate and optimized electronic configuration. When used as bifunctional electrocatalysts toward alkaline overall water splitting, MoOx/Fe1−xS/IF delivers a current density of 10 mA cm−2 at a low cell voltage of 1.56 V for 110 h. Such high performance coupled with low-cost iron-based materials suggests that the present strategy may open new avenues for the rational design of electrocatalysts and for use in practical water splitting. [ABSTRACT FROM AUTHOR]

Cubic core–shell NiCoSx/CoS2 composite catalyst was successfully prepared on the basis of K3[Co(CN)6]. First, Ni2+ is substituted for K+ in K3[Co(CN)6]2 to prepare the binary metal ion precursor of Ni3[Co(CN)6]2. Afterward, coating Co(OH)2 on the surface of Ni3[Co(CN)6]2 could not only maintain the cubic structure of Prussian blue analogue but also build a composite interface between two phases. After the Ni3[Co(CN)6]2/Co(OH)2 precursor is sulfided, a porous NiCoSx/CoS2 composite catalyst material with a cubic structure is obtained. NiCoSx/CoS2 catalysts showed excellent oxygen evolution reactions and oxygen reduction reactions. The overpotential was only 310 mV to achieve a current density of 20 mA cm−2 and the half-wave potential can reach 0.80 V. During the exploration of the hydrogen evolution reaction, the catalyst exhibited 253 mV overpotential at 10 mA cm−2. When this catalyst was used in Zn–air batteries as the cathode, it showed excellent cycle stability (210 h) and small voltage gap (0.80 V) at 5 mA cm−2. Meanwhile, soft-pack flexible batteries assembled with NiCoSx/CoS2 can be charged and discharged stably at any bending angle. [ABSTRACT FROM AUTHOR]

In order to lower energy consumption it is critical to develop highly efficient and stable non-precious metal bifunctional catalysts. In this study, we found that rational design of novel nanostructures is able to increase the number of active sites, conductivity and accelerate electron transfer, thus promoting enhanced performance of the catalyst. We successfully synthesized carbon nanotubes (CNTs) containing a hollow polyhedral (CNTHPs) structure through annealing, etching and phosphating. The unique hollow shape not only provides a stable structure but also facilitates mass and charge transfer. Thus, CoP/CNTHPs can catalyze the hydrogen and oxygen evolution reactions effectively with overpotentials of 147 and 238 mV at 10 mA cm−2. Simultaneously, CoP/CNTHPs only needs a voltage of 1.54 V to attain a current density of 10 mA cm−2 in the electrocatalytic water splitting process, demonstrating its bifunctional activity. Furthermore, the electrolytic catalytic performance does not weaken significantly after 12 hours of electrolysis, demonstrating excellent stability. Overall, this research offers useful insights into rational design of high-performance non-noble metal catalysts. [ABSTRACT FROM AUTHOR]

Designing catalysts with high electrochemical activity and stability for the oxygen evolution reaction (OER) is a pivotal step for sustainable water splitting. Interface engineering can represent a practical approach to enhance catalytic performance. In this work, a cyclic voltammetry (CV) technique as an intentional surface reconstruction strategy is utilized to promote FeCoNiCrVB as a highly active OER catalyst. The activated electrocatalyst manifests enhanced catalytic activity with a low overpotential of 237 mV at a current density of 10 mA cm-2 and a Tafel slope of 24.2 mV dec-1, compared with the pristine one (332 mV & 46.2 mV dec-1). The excellent activity and long-term stability make reconstructed FeCoNiCrVB a promising candidate to catalyze the OER process. The amorphous state, highly active sites and entropy engineering jointly contribute to its advanced OER performance. This work shows the great potential of multicomponent alloys as electrocatalysts, and provides new ideas for the enhancement of the OER activity by using an electrochemical surface reconstruction strategy. [ABSTRACT FROM AUTHOR]

The efficiency and cost of electrocatalysts are critical factors restricting their application in water electrochemical decomposition. In recent years, transition metal carbides (TMCs) have been highlighted due to their unique characteristics for water splitting: good conductivity and stability. However, their electrochemical performance required further optimization. In this work, a distinct non-solvent method was utilized to achieve a Ni3ZnC0.7-Mo2C/Ni foam (NF) catalyst, which exhibited a nanoflower structure with efficient exposed active sites. Moreover, the synergistic effect between the Mo and Ni species greatly affected its HER and OER performance. Ni3ZnC0.7-Mo2C/NF showed excellent electrocatalytic performance with small overpotentials of 58 mV and 257 mV at 10 mA cm−2 for the HER and OER, respectively. To our delight, the overall water splitting could be driven by only 1.56 V. This work not only demonstrates an excellent bifunctional electrocatalyst for overall water splitting but also provides another method for polymetallic carbide preparation and activity optimization. [ABSTRACT FROM AUTHOR]

The development of efficient and low-cost catalysts is of great significance for the future application of the electrocatalytic hydrogen evolution reaction (HER). Herein, a series of Ni,N co-doped Mo2C nanostructures (Nix–Mo2C/N) with different Ni content levels are fabricated. The phase-directing effect of Ni on Mo2C/N is observed, which is in charge of the phase transformation of Mo2C/N from an α- to a β-phase. At the optimized Ni-doping level, biphase Ni15–Mo2C/N exhibits outstanding HER activity under both acidic and alkaline conditions. In particular, under alkaline conditions, Ni15–Mo2C/N delivers an overpotential of only 105.0 mV, accompanied by a low Tafel slope of 44.96 mV dec−1. The performance is comparable to commercial 20% Pt/C and higher than most state-of-the-art Mo2C-based catalysts as well. [ABSTRACT FROM AUTHOR]

Developing high-efficiency and low-cost catalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is of great significance for the commercialization of rechargeable metal–air batteries. Herein, we demonstrated the construction of graphited carbon-coated FeTiO3 (FeTiO3@C) via in situ annealing Ti3C2Tx nanosheets in a rusted-reactor and its efficient bifunctional activity for rechargeable Zn–air batteries (RZABs). The electron-transport dynamics of FeTiO3@C can be improved by using highly conductive graphited carbon derived from Ti3C2Tx. The FeTiO3@C catalyst annealed at 500 °C exhibits excellent OER and ORR activities. Specifically, FeTiO3@C shows a low overpotential of 323 mV at 10 mA cm−2 and a small Tafel slope of 53 mV dec−1 towards the alkaline OER. During the OER process, FeTiO3@C can be partially converted into highly active iron oxyhydroxide via in situ electrochemical reconstruction, which serves as the active species. After being assembled to RZABs, it shows an open-circuit potential of 1.33 V, a high trip efficiency of 63.4% and long-time cycling stability. This work can provide a new avenue for developing bifunctional electrocatalysts for RZABs used in portable devices. [ABSTRACT FROM AUTHOR]

Hydrogen generation by water splitting using various renewable energy sources will play an important role in the sustainable green energy supply of the future. Unfortunately, wide industrial adoption of this process is currently impeded by the necessity to use noble metal based electrolysis catalysts. In this study, a low-cost and highly efficient water electrolysis catalyst active in the hydrogen evolution reaction (HER) taking place in alkaline medium is developed. The catalyst preparation procedure consists of electrodeposition of a rough nickel layer onto a smooth copper mesh, followed by the growth of hierarchical Ni nanowires on its surface. The rough nickel layer provides plenty of active sites for nanowire formation, resulting in a synergetic effect between copper and nickel in the copper mesh supported nickel nanowire array, which effectively enhances the HER electrocatalytic performance of this novel material. The catalyst demonstrated an HER overpotential as low as 317 mV in 1 M KOH electrolyte at a current density of 1 A cm−2. The copper substrate's superior electrical conductivity to that of nickel is responsible for the excellent HER performance of the catalyst at high current density, making it a promising candidate to replace highly expensive noble metal based electrodes. [ABSTRACT FROM AUTHOR]

Recently, much attention has been focused on the development of photocatalysts for hydrogen evolution. Up to now, efficient hydrogen generation is still greatly challenging due to the restraints of the surface redox reaction rate, and the introduction of a co-catalyst is one of the keys to this problem. Here, dual non-noble co-catalysts NixP and Mn3O4 were proposed and prepared on a g-C3N4/red phosphorus (CNP) hybrid structure with a high light adsorption capability by a two-step photo-deposition method. The photo-excited charge on the composite catalyst separate and transfer from C3N4 to red phosphorous due to a type I heterojunction structure. NixP and Mn3O4 act as reductive and oxidative co-catalysts, respectively. The hydrogen production rate was 5851.3 μmol g−1 h−1, 12.4 times that of pure CNP. The consistent catalytic activity in an actual 25 mL flask for hydrogen evolution over eight hours accumulated 245.08 μmol H2 under solar simulated irradiation. This work provides practical reference for the development of a novel inexpensive photocatalyst system. [ABSTRACT FROM AUTHOR]

Currently, two-dimensional (2D) layered transition metal chalcogenides (TMCs), especially MoS2, are attracting widespread attention in the field of water electrolysis. Unfortunately, the catalytic activity of MoS2 is limited to a few edge sites and by its low conductivity. Herein, MoS2/NiS heterostructures possessing a flower-like morphology were constructed via an accurate thermal treatment process to realize precise interface modification. As expected, through the adjunction of a certain amount of polyvinylpyrrolidone, NiS grew uniformly on the surface of MoS2 nanosheets, thereby forming a large number of visual lattice fringes with a specific interplanar spacing, which promoted a higher electron-transfer efficiency. The better electron-transfer efficiency resulted in a better hydrogen evolution reaction performance, providing an overpotential of 158 mV at 10 mA cm−1, a Tafel slope of 128.1 mV dec−1, and significantly long-term durability. Moreover, density functional theory calculation also showed that the precise interface modification of MoS2/NiS heterostructure exhibited more occupations at the Fermi level, which improved the electrical conductivity. Additionally, the MoS2/NiS catalysts achieved a moderately lower hydrogen adsorption energy (ΔGH*), indicating that it had better catalytic hydrogen evolution performance. This work can be extended to design other catalytic materials and for understanding reactions in the fields of energy conversion through theoretical calculations. [ABSTRACT FROM AUTHOR]

The substitution of C for N in graphitic carbon nitride (g-C3N4) can promote π-electron availability and increase photocatalytic activity, but the low specific surface area still limits its performance. Herein, porous C-doped g-C3N4 was prepared by the uracil-mediated supramolecular assembly of melamine and cyanuric acid. The as-prepared catalyst exhibited a high photocatalytic hydrogen evolution rate of 2352 μmol g−1 h−1 under visible light irradiation (λ ≥ 420 nm), which was 28 times that of g-C3N4 (83 μmol g−1 h−1), due to the porous architecture and C-doping effect. The porous architecture endowed the catalyst with a large specific surface area (79.4 m2 g−1) and great light utilization efficiency in the visible light region between 500 and 750 nm. In addition, C-doping modified the energy band structure of g-C3N4 to a narrow band gap (from 2.92 eV to 2.78 eV) and enhanced the separation efficiency of photogenerated carriers. [ABSTRACT FROM AUTHOR]