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The urea oxidation reaction (UOR), which possesses a low theoretical potential and superior kinetics, is an attractive substitute for the anodic oxygen evolution reaction (OER) in overall water splitting; however, the implementation of hydrogen production in overall urea splitting is impeded by the deficiency of highly efficient, durable and cost-effective catalysts. Herein, we fabricated an Ni2P–MoP2 heterostructure with a hierarchical structure grown on carbon paper (Ni–Mo–P/CP), which exhibited robust activity and outstanding durability for the electrocatalytic oxidation of urea. The Ni–Mo–P/CP catalyst possessed an ultralow potential of 1.39 V to obtain the current density of 100 mA cm−2, small Tafel slope (27 mV dec−1) and long-term durability with almost no decay within 15 h. The experimental characterization revealed that the optimized electronic structure and the synergistic effect of abundant exposed active sites in the Ni–Mo–P/CP catalyst contribute to the efficient UOR catalytic activity. This work enriches the candidate catalysts for the UOR and promotes the industrial development of hydrogen production. [ABSTRACT FROM AUTHOR]

Photosystem I/dithiol molecular wire/nanoparticle bioconjugates have been shown to photocatalytically generate dihydrogen at linear rates when continuously illuminated. In an effort to maximize H2production, the pH and ionic concentration of the solution, the mobility of the electron donor, the length and degree of saturation of the molecular wire, and the intensity of the light were systematically investigated. Optimal conditions included a solution buffered at pH 6.0, cross-linked plastocyanin, rebuilt spinach PS I, and the use of 1,4-benzenedithiol to connect PS I to the Pt nanoparticle. Illumination of this optimized Photosystem I/dithiol molecular wire/nanoparticle bioconjugate at a light intensity of 70 μE m−2s−1generated a measured one time H2production rate of 312 μmol H2mg Chl−1h−1. [ABSTRACT FROM AUTHOR]

Efficient alkaline hydrogen evolution electrodes must be used for hydrogen production in anion exchange membrane water electrolyzers (AEMWEs). Therefore, we fabricated a NiMnS catalyst with a Mn-rich surface, which was self-supported on Ti paper through one-step electrodeposition. Mn doping endowed the catalyst with a unique hollow morphology and lattice-distorted structure. Consequently, the NiMnS/Ti electrode exhibited a large number of exposed electrochemical surfaces and effective active sites and a high hydrogen evolution reaction (HER) activity. Specifically, in half-cell measurements, the NiMnS/Ti electrode exhibited an overpotential of 65 mV at 10 mA cm−2, which was lower than that of NiS/Ti (102 mV) and indicated its superior HER activity. When the proposed cathode was applied in an AEMWE single cell, the device achieved a high current density of up to 0.9 A cm−2 at a cell potential of 2.0 V. [ABSTRACT FROM AUTHOR]

Platinum-based catalysts exhibit outstanding electrocatalytic performance in the hydrogen evolution reaction (HER). However, platinum-based catalysts face significant challenges due to their rarity and high cost. This paper endeavors to shed light on a promising alternative: polyoxometalate (POM)-based catalysts, which possess significant potential for the synthesis of non-noble metal-based catalysts for the HER. Utilizing POMs as raw materials to assemble POM-derived materials, including POM-derived crystalline materials, metal sulfides, phosphides, carbides, nitrides, and so on, has emerged as an effective approach for the synthesis of hydrogen evolution electrocatalysts. This approach offers advantages in both stability and electrocatalytic performance. This comprehensive review navigates through latest progress in the assembly strategy and HER performance of POM-based crystal materials, alongside discussion on transition metal compounds derived from POMs, such as carbides, phosphides, and sulfides. Besides, future developments in POM-derived electrocatalyst regulation of the electrochemical HER are prospected. [ABSTRACT FROM AUTHOR]

Hydrogen, highly valued for its pristine cleanliness and remarkable efficiency as an emerging energy source, is anticipated to ascend to a preeminent status within the forthcoming energy landscape. Electrocatalytic water splitting is considered a pivotal, eco-friendly, and sustainable strategy for hydrogen production. The substantial energy consumption stemming from oxygen evolution side reactions significantly impedes the commercial viability of water electrolysis. Consequently, the pursuit of a cost-effective and efficacious oxygen evolution reaction (OER) catalyst stands as an imperative strategy for realizing hydrogen production via water electrolysis. Layered metal oxides, owing to their robust anisotropic properties, versatile adjustability, and extensive surface area, have emerged as suitable candidates for OER catalysts. However, owing to the distinctive attributes of layered metal oxides, ongoing investigations into these materials are slightly fragmented, lacking universal consensus. This article comprehensively surveys the recent advancements in layered metal oxide-based OER catalysts, categorized into single metal oxides, alkali cobalt oxides, perovskites, and miscellaneous metal oxides. Initially, the main OER intermediate reaction steps of layered metal oxides are scrutinized. Subsequently, the design, mechanism, and application of several pivotal layered metal oxides in the OER are systematically delineated. Finally, a summary is provided, alongside the proposal of future research trajectories and challenges encountered by layered metal oxides, with the aspiration that this paper may serve as a valuable reference for scholars in the field. [ABSTRACT FROM AUTHOR]

This document is a back cover of the journal "Dalton Transactions: An International Journal of Inorganic Chemistry." It features research conducted by Dr. Starla D. Glover's laboratory at Uppsala University in Sweden. The research focuses on hydrogen production using a fully de novo enzyme, which is an artificial enzyme based on a three alpha-helical protein and a cobalt-based catalyst. The study demonstrates the potential of small de novo proteins as enzyme scaffolds for bioinspired catalysts, contributing to the development of efficient and sustainable hydrogen production systems. The document also mentions another research paper by Enrique Colacio et al., which discusses the control of geometry and anisotropy in cobalt complexes with tripodal ligands. [Extracted from the article]

Solar-driven water splitting offers a leading-edge approach to storing abundant and intermittent solar energy and producing hydrogen as a clean and sustainable energy carrier. More importantly, constructing well-designed photocatalysts is a promising approach to develop clean hydrogen energy. In this paper, flower spherical UiO-66-(SCH3)2/ZnIn2S4 (UiOSC/ZIS) photocatalysts are successfully synthesized by a simple two-step hydrothermal method, and they exhibit high hydrogen production activity in light-driven water splitting. The optimized 30-UiOSC/ZIS (the content of UiOSC was 30 mg) composite exhibits optimal hydrogen production activity with a hydrogen production of 3433 μmol g−1 h−1, which is 5 and 235 times higher than that of pure ZIS and UiOSC, respectively. In addition, a long-cycling stability test has shown that the UiOSC/ZIS composite has good stability and recyclability. Experimental and characterization results show the formation of a type-II heterojunction between UiOSC and ZIS. This effectively suppresses the recombination of electrons–holes and promotes the carrier transfer, thus significantly improving the hydrogen production performance. This research further promotes the application of UiO-66-(SCH3)2 in the field of photocatalytic hydrogen production and provides a reference for the rational design of UiO-66-based composite photocatalysts. [ABSTRACT FROM AUTHOR]

Electrocatalytic hydrogen generation in alkaline medium has become widely used in a variety of sectors. However, the possibility for additional performance improvement is hampered by slow kinetics. Because of this restriction, careful control over processes such as water dissociation, hydroxyl desorption and hydrogen recombination is required. Covalent organic frameworks (COFs) based on porphyrin and polyoxometalates (POMs) show encouraging electrocatalytic performance, offering a viable route for effective and sustainable hydrogen generation. Their specific architectures lead to increased electrocatalytic activity, which makes them excellent choices for developing water electrolysis as a clean energy conversion method in the alkaline medium. In this regard, TTris@ZnPor and Lindqvist POM were coordinated to create a new eco-friendly and highly active covalent organic framework (TP@VL-COF). In order to describe TP@VL-COF, extensive structural and morphological investigations were carried out through FTIR, 1H NMR, elemental analysis, SEM, fluorescence, UV-visible, PXRD, CV, N2-adsorption isotherm, TGA and DSC analyses. In an alkaline medium, the electrocatalytic capability of 20%C/Pt, TTris@ZnPor, Lindqvist POM and TP@VL-COF was explored and compared for the hydrogen evolution reaction (HER). The TP@VL-COF showed the best catalytic efficiency for HER in an alkaline electrolyte, requiring just a 75 mV overpotential to drive 10 mA cm−2 and outperforming 20%C/Pt, TTris@ZnPor, Lindqvist POM and other reported catalysts. The Tafel slope value also indicates faster kinetics for TP@VL-COF (114 mV dec−1) than for 20%C/Pt (182 mV dec−1) TTris@ZnPor (116 mV dec−1) and Lindqvist POM (125 mV dec−1). [ABSTRACT FROM AUTHOR]

In this paper, we present a MoP/P–Mn0.5Cd0.5S photocatalytic material (PMOMCS-Px). A novel catalyst can efficiently split water into hydrogen without precious metals. In the sacrificial agent environment, the HER (hydrogen evolution rate) of PMOMCS-P5 was 4368.25 μmol g−1 h−1 which was 11.4 times greater than the HER of Mn0.5Cd0.5S (383.19 μmol g−1 h−1), and its hydrogen production performance was better than that of Pt/Mn0.5Cd0.5S (2.0 wt% Pt). Furthermore, the hydrogen evolution performance of PMOMCS-P5 under pure water conditions was also examined, and the HER of PMOMCS-P5 was 209.76 μmol g−1 h−1, which was 20.4 times that of Mn0.5Cd0.5S (10.29 μmol g−1 h−1). Its characterization proved that the introduction of the co-catalyst MoP and P doping inhibited the recombination of e− and h+, enhanced the reduction capacity, and reduced the hydrogen precipitation reaction overpotential of PMOMCS-Px, thus enhancing the hydrogen production performance of PMOMCS-Px. Therefore, an efficient and economical photocatalyst was prepared. [ABSTRACT FROM AUTHOR]

The electrolysis of water, particularly proton exchange membrane (PEM) water electrolysis, holds great promise for hydrogen production in industry. However, the catalyst used in this process is prone to dissolution in acidic environments, making it imperative to develop cost-effective, highly efficient, and acid-stable electrocatalytic materials to overcome this challenge and enable large-scale application of PEM water electrolysis technology. Herein, we prepared ruthenium oxide (RuO2)/graphitic carbon nitride (g-C3N4) composites (RuO2/C3N4) via a combination of sol–gel and annealing methods. The g-C3N4 provides a large surface area, while RuO2 is uniformly deposited on the g-C3N4 surface. The interaction between g-C3N4 and RuO2 stabilizes the RuO2 nanoparticles and enhances long-term water oxidation stability. This unique structure and the combined advantages of RuO2 and g-C3N4 yield exceptional electrocatalytic activity toward both the oxygen evolution reaction (OER, 240 mV@10 mA cm−2) and the hydrogen evolution reaction (HER, 109 mV@10 mA cm−2), with excellent durability (over 28 h), and a cell voltage of 1.607 V at 10 mA cm−2 when used in an RuO2/C3N4‖‖RuO2/C3N4 electrolyzer. This study highlights the efficacy of the g-C3N4 support method in designing highly stable Ru-based OER electrocatalysts for efficient acidic water splitting. [ABSTRACT FROM AUTHOR]

To develop hydrogen energy production and address the issues of global warming, inexpensive, effective, and long-lasting transition metal-based electrocatalysts for the synthesis of hydrogen are crucial. Herein, a porous electrocatalyst NiMo/Ni/NF was successfully constructed by a two-step electrodeposition process, and was used in the hydrogen evolution reaction (HER) of electrocatalytic water decomposition. NiMo nanoparticles were coated on porous Ni/NF grown on nickel foam (NF), leading to a resilient porous structure with enhanced conductivity for efficient charge transfer, as well as distinctive threedimensional channels for quick electrolyte diffusion and gas release. Notably, the low overpotential (42 mV) and fast kinetics (Tafel slope of 44 mV dec-1) at a current density of 10 mA cm-2 in 1.0 M KOH solution demonstrate the excellent HER activity of the electrode, which was superior to that of recently reported non-noble metal-based catalysts. Additionally, NiMo/Ni/NF showed extraordinary catalytic durability in stability tests at a current density of 10 mA cm-2 for 70 h. The porous structure catalyst and the electrodeposition-electrocatalysis technique examined in this study offer new approaches for the advancement of the electrocatalysis field because of these benefits. [ABSTRACT FROM AUTHOR]

Constructing an environmentally friendly and efficient electrocatalyst holds important and profound significance for energy-efficient hydrogen production. Replacing the oxygen evolution reaction with a lower potential urea oxidation reaction (UOR) may save energy in water electrolysis to produce hydrogen. The UOR is characterized by its high energy barrier, which results in slow reaction kinetics. In this study, we introduced Ba(OH)2 into Ni(OH)2 to form uniform nanosheets. Due to the introduction of Ba2+, the lattice expansion of Ni(OH)2 was triggered, leading to significant improvement in UOR activity. The catalyst achieved a current density of 100 mA cm-2 at only 1.316 V and exhibited remarkable stability over time. Density functional theory (DFT) calculations demonstrate that the Ba-Ni(OH)2 site significantly reduces the energy barrier for urea adsorption, intermediate steps, and desorption. This work provides a novel and environmentally friendly strategy for constructing energy-efficient and highly efficient catalysts through the doping of alkaline earth metals. [ABSTRACT FROM AUTHOR]

To date, researchers in chase of economic cost-efficiency are faced with the problem of developing effective catalysts for water splitting without the use of platinoids. Herein, catalytic properties of hexanuclear rhenium cluster complexes are investigated in application to the hydrogen evolution reaction (HER). A paste composite electrode containing the cluster complexes was obtained, producing a current density of 10 mA cm−2 at an extraordinarily low overpotential of 90 mV (RHE). The {Re6Se8}-based complexes have shown very favorable reaction kinetics via 102 mV dec−1 value of the Tafel slope for HER reaction within the composition of the paste electrode. Model calculations of kinetic parameters using density functional theory also support the experimental findings. This work underscores the perspectivity of rhenium cluster compounds in HER and opens a promising avenue toward the practical implementation of hydrogen production through electrochemical water splitting. [ABSTRACT FROM AUTHOR]

Metal halide perovskites, such as iodine methylamine lead (MAPbI3), have received extensive attention in the field of photocatalytic decomposition of HI for hydrogen evolution, due to their excellent photoelectric properties. In this paper, a new MAPbI3-based composite, MoC/MAPbI3, was synthesized. The results show that 15 wt% MoC/MAPbI3 has the best hydrogen production performance (38.4 μmol h−1), which is approximately 24-times that of pure MAPbI3 (1.61 μmol h−1). With the extension of the catalytic time, the hydrogen production rate of MoC/MAPbI3 reached 165.3 μmol h−1 after 16 h due to the effective separation and transfer of charge carriers between MoC and MAPbI3, showing excellent hydrogen evolution rate performance under visible light. In addition, the cycling stability of MoC/MAPbI3 did not decrease in multiple 4 h cycle tests. This study used the non-precious metal promoter MoC to modify MAPbI3, and provides a new idea for the synthesis of efficient MAPbI3-based composite catalysts. [ABSTRACT FROM AUTHOR]

The development of low-cost, high-efficiency, and stable electrocatalysts for the alkaline hydrogen evolution reaction (HER) is a key challenge because the alkaline HER kinetics is slowed by an additional water dissociation step. Herein, we report an interfacial engineering strategy for polyoxometalate (POM)-stabilized nickel (Ni) quantum dots decorated on the surface of porous titanium mesh (POMs–Ni@PTM) for high-rate and stable alkaline hydrogen production. Benefiting from the strong interfacial interactions among POMs, Ni atoms, and PTM substrates, as well as unique POM–Ni quantum dot structures, the optimized POMs–Ni@PTM electrocatalyst exhibits a remarkable alkaline HER performance with an overpotential (η10) of 30.1 mV to reach a current density of 10 mA cm−2, which is much better than those of bare Ni decorated porous titanium mesh (Ni@PTM) (η10 = 171.1 mV) and POM decorated porous titanium mesh (POMs@PTM) electrocatalysts (η10 = 493.6 mV), comparable to that of the commercial 20 wt% platinum/carbon (20% Pt/C) electrocatalyst (η10 = 20 mV). Moreover, the optimized POMs–Ni@PTM electrocatalyst demonstrates excellent stability under continuous alkaline water-splitting at a current density of ∼100 mA cm−2 for 100 h, demonstrating great potential for its practical application. [ABSTRACT FROM AUTHOR]

Using electrochemical water splitting to generate hydrogen is considered a desirable approach, which is greatly impeded by the sluggish dissociation of H2O and adsorption and desorption of H*. Effective hydrogen production can be achieved by speeding up the chemical process with a suitable electrocatalyst. In this work, we designed and synthesized a rare earth element cerium (Ce) regulated iron–nickel bimetallic phosphide Ce-NiFeP@NF (here NiFeP represents Fe2P/NiP2) nanoarray with nanoflowers. For the hydrogen evolution reaction (HER), Ce-NiFeP@NF only needs an overpotential of 106 mV to provide a current density of 10 mA cm−2, compared to NiFeP@NF (175 mV@10 mA cm−2). This self-supported electrocatalyst Ce-NiFeP@NF with a composite morphology exhibits excellent performance in the HER. Specifically, the introduction of Ce promotes the electron transfer process at the Fe2P/NiP2 heterojunction interface and the Ce-NiFeP@NF nanocomposite structure with nanoflowers has a larger electrochemically active specific surface area, which is more conducive to improving the intrinsic catalytic activity. Also, a dual-electrode alkaline electrolytic cell (Ce-NiFeP@NF functions as both the anode and the cathode) operates with a cell voltage of only 1.56 V to achieve a current density of 10 mA cm−2. The synergistic effect of rare earth element doping and heterojunction engineering can improve the morphology of intrinsic catalysts to achieve more efficient electrochemical water splitting for hydrogen production. [ABSTRACT FROM AUTHOR]

Hydrazine-assisted electrochemical water splitting is an important avenue toward low cost and sustainable hydrogen production, which can significantly reduce the voltage of electrochemical water splitting. Herein, we took a simple approach to fabricate NiFeP nanosheet arrays on nickel foam (NiFeP/NF), which exhibit superior electrocatalytic activity for the hydrogen evolution reaction (HER) and the hydrazine oxidation reaction (HzOR). Our investigations revealed that the excellent electrocatalytic activity of NiFeP/NF mainly arises from the bimetallic synergistic effect, abundant electrocatalytically active sites facilitated by the porous nanosheet morphology, high intrinsic conductivity of NiFeP/NF and strong NiFeP–NF adhesion. We assembled a hydrazine-boosted electrochemical water splitting cell using NiFeP/NF as a bifunctional catalyst for both electrodes, and the overall hydrazine splitting (OHzS) exhibits a considerably low overpotential (100 mV at 10 mA cm−2), and is stable for 40 h continuous electrolysis in a 1 M KOH + 0.5 M N2H4 electrolyte. When it is applied to hydrogen production by seawater electrolysis, its catalytic activity shows strong tolerance. This work provides a promising approach for low cost, high-efficiency and stable hydrogen production based on hydrazine-assisted electrolytic seawater splitting for future applications. [ABSTRACT FROM AUTHOR]

A bifunctional catalyst used for urea oxidation-assisted hydrogen production can efficiently catalyze the urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) simultaneously, thus simplifying electrolytic cell installation and reducing the cost. Constructing the heterointerface of two components or species and doping heteroatom are effective strategies to improve the performance of electrocatalysts, which could regulate the local electronic structure of the catalysts at their interface region, adjust their orbital overlap, and achieve enhanced catalytic performance. In this study, a simple hydrothermal method was studied for the preparation of B-doped Ni5P4/Ni2P heterostructures on nickel foam (B-Ni5P4/Ni2P@NF). Under 1 M KOH at a current density of 10 mA cm−2, an overpotential of 76 mV was obtained for the HER. When 0.3 M urea was added to 1 M KOH, the performance of the prepared catalyst was greatly improved. When the current density reached 10 mA cm−2, the potential was only 1.35 V. In addition, urea-assisted overall water splitting voltage was only 1.41 V. Thus, the B-Ni5P4/Ni2P catalyst possess excellent electrocatalytic activity. The main reason for the excellent properties of the electrocatalyst is the construction of heterostructure, which regulates the electronic structure of the catalyst at its interface and generates a new efficient active site. In addition, the doping of B atoms further promotes the charge transfer rate, thus strengthening the interaction between two phases and improving the catalytic performance. This study provides a simple, environmentally friendly, and rapid design method to prepare an active bi-functional electrocatalyst that has a positive effect on urea-assisted overall water splitting. [ABSTRACT FROM AUTHOR]

As a two-dimensional (2D) nanomaterial, bulk g-C3N4 (CNB) has a low specific surface area and weak electron transport ability, which limit its application in photocatalysis. In this paper, ultrathin porous g-C3N4 nanosheets (CNS) have been synthesized by thermal oxidation etching of CNB. Compared with CNB, CNS possess a larger surface area of 234.65 m2 g−1, good dispersity in water and a high electron transfer rate. As a co-catalyst, ultra-small Pt nanoparticles (NPs) with high dispersity are successfully loaded on the surface of CNS. It is found that changing the loading method of Pt NPs in the preparation step remarkably alters the efficiency for hydrogen production. The Pt/CNS-CR photocatalyst fabricated by the chemical reduction (CR) method shows a much higher efficiency for H2 evolution from water splitting, compared to the Pt/CNS-PR photocatalyst obtained by the loading of Pt NPs by the traditional photo-reduction (PR) method. When triethanolamine (TEOA) is used as a hole sacrificial agent, the hydrogen production rate of 2.0%-Pt/CNS-CR is 7862.5 μmol g−1 h−1, which is 6.92 times higher than that of 2.0%-Pt/CNS-PR (1136.8 μmol g−1 h−1). The valence states of the Pt element in the Pt/CNS-CR and Pt/CNS-PR nanocomposites have been analyzed by X-ray photoelectron spectroscopy, respectively. At the same time, the effects of the loading amount of Pt and different sacrificial reagents on the photocatalytic H2 generation activity have also been systematically investigated. [ABSTRACT FROM AUTHOR]

By providing the spatial separation of the active sites and retaining high oxidative and reducing capacity, the direct Z-scheme heterostructure is considered the most potential structure for yielding photo-electric response. However, challenges still exist in the directional transfer of charge carriers between two semiconductors in direct Z-scheme structures. In this regard, by constructing the Vzn defect and p–n junction, a direct Z-scheme ZnxCd1−xS@ZnS-NiS heterostructure was obtained for the regulated electronic structure, which ensured high-yield hydrogen properties. The Zn vacancy in the partially-coated ZnS shell led to the Vzn energy level, and the addition of NiS led to the p–n structure, which caused a drastic downshift of the band edge potentials in comparison to that of pristine CdS. This variation gave rise to a staggered band edge alignment between ZnxCd1−xS and NiS, resulting in the variation of charge transfer kinetics from type-I to direct Z-scheme. Through careful characterization, it was found that the optimal photocatalytic hydrogen precipitation activity reached 16 683.6 μmol g−1 h−1, which was 70 times that of CdS, and this improvement was considered to form a spatial barrier, providing a clear direction and path for carrier transmission. [ABSTRACT FROM AUTHOR]

With the exceptional advantages of safety, greenness, and low cost, photocatalytic H2O2 generation has kindled a wonderful spark, although being severely hampered by the terrible photoinduced exciton recombination, migration, and surface decomposition. Here, employing reflux method, the Cd–Mo–Se quantum dots of varying molar ratios of Cd and Mo were synthesized using thioglycolic acid as the capping ligand to regulate their growth. This type of metal alloying promotes rapid charge migration, improves light harvesting, and reduces the rate of charge recombination. The improved optoelectronic properties and boosted activity of Cd-rich ternary CMSe-1 QDs led to the observed exceptional photocatalytic H2O2 yield of 1403.5 μmol g−1 h−1 (solar to chemical conversion efficiency, 0.27%) under visible light, outperforming the other ternary and Se-based QD photocatalysts. Additionally, CMSe-1 shows 93.6% (2 h) hazardous Cr(VI) photoreduction. The enhanced catalytic performance of CMSe-1 corresponds to effective charge carrier separation and transfer efficiency, well supported by PL, TRPL, and electrochemical measurements. Photocatalytic H2O2 production was also studied under varying experimental conditions and the scavenger test suggests a superoxide radical intermediate 2-step single electron reduction pathway. The catalyst-assisted Cr(VI) reduction is substantiated by the zero-order kinetics as well as the determination of the pHPZC value. The catalyst can be employed for a maximum of four times while retaining its activity, according to the photostability and reusability test outcomes. This research presents interesting approaches for producing ternary QDs and modified systems for efficient photocatalytic H2O2 production and Cr(VI) reduction. [ABSTRACT FROM AUTHOR]

The electrocatalytic hydrogen evolution reaction (HER) is an ideal method for hydrogen production. Transition metal complex electrocatalysts exhibit poor HER activity due to excessive or weak adsorption of H during the electrochemical reduction of water to molecular hydrogen in acidic environments. Developing specific functional complex materials as desired catalysts is challenging. Here, an electrochemical surface restructuring strategy of polyoxometalate (POM)-modified Ag materials toward the HER with a dramatically decreased overpotential under acidic aqueous conditions is established. We prepared two POM [SiW12O40]4− (SiW12)/[P2W18O62]6− (P2W18)-based Ag-2,2′-biimidazole (H2biim) inorganic–organic hybrid compounds (1 and 2) via the hydrothermal method and these two compounds undergo an electrochemical restructuring process in 0.5 M H2SO4 during the HER, in which Ag nanoparticles are in situ formed with the basic structures of SiW12 and P2W18 being maintained. The activated catalysts (1-AC-RDE and 2-AC-RDE) exhibit good electrocatalytic activity for the HER with good long-term stability, and the required overpotentials at a current density of 10 mA cm−2 are 112 mV (1-AC-RDE) and 91 mV (2-AC-RDE) with Tafel slopes of 77 mV dec−1 and 65 mV dec−1, respectively. The excellent electron–proton storage and transferability of SiW12 and P2W18 may provide a solution for the insufficient capture of H by Ag, leading to an effective self-optimizing behavior and superior acidic HER activity. [ABSTRACT FROM AUTHOR]

The development of an efficient noble-metal-free cocatalyst is the key to photocatalytic hydrogen production technology. In this study, hierarchical Co(OH)2 nanosheet array-graphene (GR) composite cocatalysts are developed. With Eosin Y (EY) as a photosensitizer, the optimal Co(OH)2-10%GR hybrid cocatalyst presents excellent photocatalytic activity with an H2 production rate of 17 539 μmol g−1 h−1, and the apparent quantum yield for hydrogen production can reach 12.8% at 520 nm, which remarkably surpasses that of pure Co(OH)2 and most similar hybrid cocatalyst systems. Experimental investigations demonstrate that the excellent photocatalytic activity of Co(OH)2-GR arises from its unique nanosheet array architecture, which can collaboratively expose rich active sites for photocatalytic hydrogen evolution and facilitate the migration and separation of photogenerated charge carriers. It is desired that this study would supply a meaningful direction for the rational optimization of the constitute and structure of cocatalysts to achieve efficient photocatalytic hydrogen generation. [ABSTRACT FROM AUTHOR]

Piezocatalytic hydrogen evolution has emerged as a promising field for the collection and utilization of mechanical energy, as well as for generating sustainable energy throughout the day. Hexagonal CdS, an established semiconductor photocatalyst, has been widely investigated for its ability to split water into H2. However, its piezocatalytic performance has received less attention, and the relationship between its structure and piezocatalytic activity remains unclear. In this study, we prepared 3D ultrathin CdS nanoflowers with high voltage electrical response and low impedance. In pure water, without the use of any cocatalyst, CdS exhibited a piezoelectric catalytic hydrogen production rate of 1.46 mmol h−1 g−1, which was three times higher than that of CdS nanospheres (0.46 mmol h−1 g−1). Furthermore, the value-added oxidation product H2O2 was produced during the process of piezoelectric catalysis. These findings provide new insights for the design of high-efficiency piezoelectric catalytic hydrogen production. [ABSTRACT FROM AUTHOR]

Photoinduced electron-separation and -transport processes are two independent crucial factors for determining the efficiency of photocatalytic hydrogen production. Herein, a sulfur vacancy defect-decorated CoSx@In2S3 (CoSx@VS-In2S3) core/shell heterojunction photocatalyst was synthesized via an in situ sulfidation method followed by a liquid-phase corrosion process. Photocatalytic hydrogen evolution experiments showed that the CoSx@VS-In2S3 nanohybrids delivered an attractive photocatalytic activity of 4.136 mmol h−1 g−1 under visible-light irradiation, which was 8.23 times higher than that of the pristine In2S3 samples. As expected, VS could enhance the charge-separation efficiency of In2S3 through rearranging the electrons of the In2S3 basal plane, in addition to improving the electron-transfer efficiency, as visually verified by transient absorption spectroscopy. Mechanism studies based on density functional theory calculations confirmed that the In atoms adjacent to VS played a key role in the translation, rotation, and transformation of electrons for water reduction. This scalable strategy focused on defect engineering paves a new avenue for the design and assembly of 2D core/shell heterostructures for efficient and robust water-splitting photocatalysts. [ABSTRACT FROM AUTHOR]

The hydrogen evolution reaction (HER) is important for "green" hydrogen production from water electrolysis. Nowadays, there is an urgent need to construct highly efficient electrocatalysts to boost the HER and achieve hydrogen production. Herein, we present the preparation of a new composite Co-Mo bimetallic sulfide supported on carbon cloth (MoS2/CoS2/CC) via a one-pot hydrothermal sulfurization strategy using (C3H5N2)6[CoMo12O40]·10H2O (CoMo12) as a metal source and thiourea as a sulfur source. The obtained MoS2/CoS2/CC catalyst exhibited outstanding HER ability, with an overpotential of 69 mV when the current density is 10 mA cm−2 in KOH solution, showing comparable performance with those of the advanced Pt/C electrodes tested under the same conditions. Additionally, the results of XRD after the catalytic reaction showed that the electrode had excellent stability in the electrolyte of 1.0 M KOH. [ABSTRACT FROM AUTHOR]

The aggravating extreme climate changes and environmental pollution problems have stimulated the exploration of green alternatives to conventional fossil fuels and green environmental treatments. Photocatalysis is recognized as an outstanding green tool for solving the energy crisis and environmental rehabilitation issues. Restricted by the high cost of precious metals, researchers expect to obtain low-cost, efficient and stable photocatalysts. Herein, CdS materials were derived through MOFs and subsequently combined with CoO to form CdS/CoO heterojunctions. The catalytic ability was evaluated by the photocatalytic degradation of tetracycline hydrochloride (TC) and the photocatalytic production of hydrogen. With the integration of CoO, in terms of TC degradation, CdS/CoO heterojunctions can degrade over 90% of TC within 1 hour. In terms of hydrogen production, compared to CdS alone, the hydrogen production efficiency of the CdS/CoO heterojunction increased by 1.7 times. The initial analysis of the reasons for the enhancement of photocatalytic efficiency was conducted by TEM, XPS and other characterization means. Density functional theory (DFT) calculations verified the existence of a built-in electric field in the CdS/CoO heterojunction, which was the essential reason for the improved catalytic performance, and finally, the presence of ˙O2− and ˙OH in the photocatalytic system was demonstrated by the ESR technique. Based on the carrier separation/transfer pathway in the heterojunction, a simple and novel S-type heterojunction scheme was proposed. [ABSTRACT FROM AUTHOR]

Modulating the coordination environment of single-atom catalysts is considered an effective way to boost the electrocatalytic activity of the hydrogen evolution reaction. Herein, a novel electrocatalyst comprising high-density low-coordination Ni single atoms anchored on Ni-embedded nanoporous carbon nanotubes (Ni–N–C/Ni@CNT-H) is constructed through a self-template assisted synthetic strategy. We demonstrate that the in situ generated AlN nanoparticles not only serve as the template for the formation of the nanoporous structure, but also contribute to the coordination between Ni and N atoms. Benefiting from the optimized charge distribution and hydrogen adsorption free energy of the unsaturated Ni–N2 active structure and nanoporous structure of the carbon nanotube substrate, the resultant Ni–N–C/Ni@CNT-H exhibited outstanding electrocatalytic hydrogen evolution activity with a low overpotential of 175 mV at a current density of 10 mA cm−2, and a long-term durability for over 160 h in continuous operation. This work provides a new insight and approach to the design and synthesis of efficient single-atom electrocatalysts toward hydrogen fuel production. [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]

Among carbon allotropes, 2D graphdiyne (GDY) possesses the merits of good ductility, strong conductivity and an adjustable energy band structure. In this study, a GDY/ZnCo-ZIF S-scheme heterojunction photocatalyst has been successfully prepared by a low-temperature mixing method. Using eosin as a photosensitizer and triethanolamine as a solvent, the hydrogen production of the GDY/ZnCo-ZIF-0.9 composite reaches 171.79 μmol, which is 6.67 and 13.5 times that of the GDY and ZnCo-ZIF materials, respectively. The apparent quantum efficiency of the GDY/ZnCo-ZIF-0.9 composite at 470 nm is 2.8%. The improved photocatalytic efficiency may be attributed to the creation of an S-scheme heterojunction structure that enables efficient separation of space charges. In addition, the EY-sensitized GDY/ZnCo-ZIF catalyst endows the GDY with a special structure to provide an abundance of electrons for the ZnCo-ZIF material, thus facilitating the photocatalytic reduction reaction to produce hydrogen. A novel perspective is presented in this study regarding the construction of an S-scheme heterojunction based on graphdiyne for efficient photocatalytic hydrogen generation. [ABSTRACT FROM AUTHOR]

To improve the photocatalytic performance of semiconductor catalysts, one of the most widely used strategies is to combine two or more semiconductors with appropriate energy band structures to construct heterojunctions for an extended light absorption range and effective charge separation. Here, a novel Z-scheme heterojunction is fabricated via the Cd0.3Zn0.7S twin crystal and the narrow band gap semiconductor Ag3PO4. The resulting Cd0.3Zn0.7S/1%Ag3PO4 photocatalyst exhibits excellent photocatalytic hydrogen production capability (167.29 μmol h−1), which is two times higher than that of Cd0.3Zn0.7S and 44/7 times higher than that of pristine ZnS/CdS. The excellent photocatalytic performance is not only attributed to the defective twin crystal structure of Cd0.3Zn0.7S but also related to the well-matched Z-scheme interface between Cd0.3Zn0.7S and Ag3PO4, and both factors effectively promote the separation of the photogenerated electron–hole pairs and prolong the lifetime of the carriers, being responsible for the excellent photocatalytic hydrogen evolution performance of the catalysts. This strategy provides new insights into the construction of efficient twin crystal heterojunctions for photocatalytic hydrogen evolution with high performance. [ABSTRACT FROM AUTHOR]

The exploitation of an extraordinary and low-cost electrocatalyst to solve energy shortage and environmental pollution issues is crucial. Herein, a topological Archimedean polyhedron of CoFe PBA (Prussian blue analogue) was synthesized via a Sn-induced crystal growth regulation strategy. After phosphating treatment of the as-prepared Sn-CoFe PBA, a Sn-doped binary CoP/FeP hybrid was obtained (Sn-CoP/FeP). Benefiting from the rough polyhedral surface and internal porous structure of Sn-CoP/FeP, when served as a highly efficient electrocatalyst, it exhibited outstanding HER performance, i.e., to drive a current density of 10 mA cm−2, it required a low overpotential of 62 mV in alkaline medium, along with a long-term cycling stability for 35 h. This work is of great significance for the development of indispensable novel catalysts for hydrogen production, and would shed new light on the topology-related performance of electrocatalysts for energy storage and conversion. [ABSTRACT FROM AUTHOR]

Hydrogen fuel plays a ubiquitous role in empowering the sustainable green energy economy. As an eco-friendly production method for hydrogen, photo-assisted water splitting is accepted to be the most reliable. However, the fabrication of stable and efficient photocatalysts is challenging. To overcome this difficulty, here we present a novel and inexpensive oxidant-promoted ultrasonic-assisted liquid phase layer exfoliation technique to fabricate a CdS/H-MoS2 nano hybrid. The newly fabricated CdS/H-MoS2 shows a hydrogen evolution rate of 162.4 mmol g−1h−1, which is 16 times higher compared to that of CdS/Pt and 67 times higher compared to that of bare CdS. Theoretical results clearly demonstrate a built-in electrostatic potential in the heterostructure junction, and that a shift in water reduction potential plays a key role in the enhancement of hydrogen production rate. We believe that the proposed experimental strategies and theoretical studies will open up a new avenue to develop new photocatalysts with high hydrogen evolution efficiency. [ABSTRACT FROM AUTHOR]

Sustainable photocatalytic hydrogen evolution (PHE) of water splitting has been utilized to solve the serious environmental pollution and energy shortage problems over the last decade. Inorganic–organic hybrid materials could combine the organic molecules and functional inorganic blocks into unique materials through complicated physical and chemical interactions. In this paper, diethylenetriamine (DETA) was used as an organic molecule template for the synthesis of inorganic–organic Zn1−xCdxS-DETA solid solution nanoflowers (NFs) at very low temperature. The obtained Zn0.2Cd0.8S-DETA NFs exhibited the highest H2 production rate (12 718 μmol g−1 h−1), which is 1.75 times as high as that of CdS-DETA. The suitable conduction band potential and excellent visible-light absorption of Zn0.2Cd0.8S-DETA solid solution NFs are closely related to the excellent PHE activity. Furthermore, the calculation on the electronic structure provides a new understanding of the band-gap shifts of the Zn1−xCdxS-DETA solid solution hybrids and the design of novel structural photocatalysts. [ABSTRACT FROM AUTHOR]

Knowledge of the photocatalytic H2-evolution mechanism is of critical importance for water splitting, and for designing active catalysts for a sustainable energy supply. In this study, we prepared plasmon Au-modified K-doped defective graphitic carbon nitride (Au/KCNx) and then applied it in photocatalytic hydrogen-production tests. The hydrogen-production rate of the Au/KCNx photocatalyst (8.85 mmol g−1 h−1) was found to be almost 104 times higher than that of Au/g-C3N4 (0.085 mmol g−1 h−1), together with an apparent quantum efficiency of 12.8% at 420 nm. It could significantly improve the photocatalytic activities of the Au/KCNx sample, which was attributed to the synergistic effects of the plasmon effect, potassium doping, and nitrogen vacancy. In addition, the Au/KCNx photocatalyst had a large surface area, which was beneficial for photogenerated carrier separation and transfer. The novel strategy proposed here is a potential new method for the development of graphitic carbon nitride photocatalysts with obviously enhanced activities. [ABSTRACT FROM AUTHOR]

Developing high-performance and low-cost self-supporting electrodes as pH-universal electrocatalysts for the hydrogen-evolution reaction (HER) and realizing high-quality hydrogen production at a high current density are highly desirable, but are hugely challenging. We created a self-supporting electrode with a coupled hierarchical heterostructure by simple electrodeposition followed by sulfurization. It comprised oxygen-deficient molybdenum oxide (MoO3−x) and cobalt phosphide (CoP) on nickel foam (NF), which represented a highly active pH-universal electrocatalyst for the HER at a high current density. Benefiting from a plethora of catalytic active sites, improved interfacial charge transfer, and strong electronic interaction, this type of MoO3−x@CoP/NF electrode delivered a superior catalytic performance. Overpotentials of only 100 mV, 135 mV, and 400 mV were needed to realize a high current density of 1 A cm−2 in alkaline, acid and neutral media, respectively, which were superior to those of most other well-developed materials based on non-noble metals. Our experimental work demonstrates the synergistic advantages of a MoO3−x@CoP heterostructure for improving the intrinsic catalytic performance but also paves a new path for the rational design of advanced electrodes for hydrogen generation in a wide range of pH conditions. [ABSTRACT FROM AUTHOR]

Selenium-derived electrocatalysts have been well explored for electrocatalytic hydrogen evolution reactions to mimic hydrogenase-like activity; however, the stability of these synthetic mimics is yet to be enhanced. In this study, we report the synthesis and characterization of a series of 1,10-phenanthroline-cobalt(II) phenolate selenoether complexes using 1,10-phenanthroline and 6-nitro-1,10-phenanthroline-Co(II)-dichloride and substituted bis-selenophenolate ligands. The synthesized cobalt(II) phenolate selenoether complexes have been characterized by CHN analysis, mass spectrometry, single crystal XRD, and UV-visible absorption spectroscopy. These complexes show electrocatalytic proton reduction from acetic acid at an overpotential of 0.45–0.56 V vs. Fc+/Fc and surpass previously reported selenium and sulfur-containing electrocatalysts. Furthermore, gas analysis from control potential electrolysis confirms that the cobalt(II) selenoethers act as electrocatalysts to produce H2 with a faradaic efficiency of 43–83% and show a turnover number of 3.24–58.60 molcat−1. The hydrogen evolution reaction (HER) was probed using deuterated acetic acid, which demonstrates an inverse kinetic isotopic effect (KIE) and is consistent with the formation of metal hydride intermediates. Furthermore, control experiments (post-dip analysis and multiple CV studies) have been performed to support the catalysis being due to a homogeneous process. Acid titration using UV-visible spectroscopy reveals that protonation is the prior step for electrocatalysis and assists in the formation of a cobalt hydride intermediate, which upon reaction with a proton generates hydrogen gas. [ABSTRACT FROM AUTHOR]

Solar-driven hydrogen generation using single-semiconductor photocatalysts for hydrogen evolution seems to be challenging due to their poor solar to fuel conversion efficiency because of their fast charge carrier recombination. The ternary heterostructure was prepared by an advanced approach to suppress the recombination of photogenerated charge carriers and has contributed a new platform for designing highly efficient photocatalytic systems. Herein, we fabricated a ternary heterojunction with ultrathin WS2–SnS2 nanosheets and CdS nanorods, and the photocatalytic activity was studied. The optimized CdS/SnS2–WS2 (6 wt%) nanostructures were found to be highly stable and exhibited the highest hydrogen evolution rate of 232.45 mmol g−1 h−1, which was almost 93-fold higher than that of the pristine CdS nanorods. Also, Density Functional Theory (DFT) calculations confirmed that the favorable band alignment for charge transport and superior catalytic activity of the newly fabricated ternary nanostructures make them a potential candidate for solar-driven hydrogen production. [ABSTRACT FROM AUTHOR]

2-Dimensional (2D) graphitic carbon nitrate (g-C3N4) nanosheets are particularly interesting photocatalytic materials because of their large surface area and excellent photoelectric properties. However, it remains challenging to synthesize 2D g-C3N4 nanosheets with high yield and high activity simultaneously. In this work, a urea-assisted one-pot method was developed in which the decomposition of urea released NH3 gas which exfoliated bulk g-C3N4 into thin nanosheets and generated pores and wrinkles on their surface. The product g-C3N4 nanosheets therefore possessed abundant surface active sites for interaction with reactants and showed enhanced light utilization efficiency, giving rise to their improved hydrogen production activity which was 3.36 times higher than that of their bulk counterpart. Importantly, the yield of g-C3N4 nanosheets using this method was almost doubled compared to a previously reported ammonium chloride (NH4Cl) assisted method. Given that g-C3N4 nanosheets are building blocks for various photocatalysts, the current synthetic method which produces g-C3N4 nanosheets with high yield and high activity shall pave the way for high-performance photocatalytic applications such as hydrogen production and more. [ABSTRACT FROM AUTHOR]

Na-doped g-C3N4/NiO 2D/2D laminated p–n heterojunction nanosheets are fabricated by facile calcination and hydrothermal methods. The average thickness of g-C3N4 nanosheets is ∼1.388 nm, and the ultrathin structure allows for a high specific surface area and enough surface active sites, increasing the surface reactivity. The flower ball like structure of NiO increases the light utilization rate. Na doping accelerates charge separation and transport by increasing the electrical conductivity. The g-C3N4 and NiO nanosheets form 2D/2D laminated structures, and the spherical structure can suppress the agglomeration of 2D nanosheets, which could realize adequate interface contact and form efficient p–n heterojunctions. The p–n heterostructure builds an internal electric field to accelerate spatial charge separation. Under visible light irradiation, the photocatalytic degradation efficiency for ciprofloxacin and the hydrogen production rate of Na-doped g-C3N4/NiO are up to 99.0%, and 2299.32 μmol h−1 g−1, respectively, which are several times higher than those of the pristine one. The fabrication strategy for 2D/2D laminated heterojunctions may provide new insights for the preparation of novel laminated photocatalysts with high performance. [ABSTRACT FROM AUTHOR]

The development of photocatalysts enabling stable and highly efficient water splitting hydrogen production remains an open challenge in the field of energy photocatalysis. Herein, Ni2P/γ-Ga2O3 nanosheets have been reported as excellent water splitting photocatalysts. Ni2P particles and γ-Ga2O3 nanosheets were synthesized by a facile hydrothermal process. The Ni2P/γ-Ga2O3 samples were prepared by an electrostatic self-assembly method with Ni2P particles and γ-Ga2O3 nanosheets as precursors. The 0.5 wt% Ni2P/γ-Ga2O3 sample shows a photocatalytic H2-production activity as high as 2.7 mmol g−1 h−1 in pure water and 12 mmol g−1 h−1 in an aqueous methanol solution under a 125 W high pressure mercury lamp, respectively, which are much higher than those of pure γ-Ga2O3 and Pt/γ-Ga2O3 nanosheets modified with a comparable Pt content. The Ni2P component plays a role as an electron collector that promotes efficient separation of photogenerated electrons and holes, and thereby improves the efficiency of photocatalytic hydrogen production. The effects of inorganic and organic sacrificial reagents on the reaction efficiency and stability were observed and discussed. This work shows that Ni2P as a cocatalyst substituting noble metals can greatly improve the photocatalytic hydrogen production efficiency of γ-Ga2O3 compared to that in pure water and a methanol–water solution. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) have emerged as an extremely promising material for photocatalytic water splitting for hydrogen production. However, their photocatalytic performance is seriously affected by the properties of their donors, acceptors and linkages. So far, few studies have been reported on the key roles of the linkages of a specific COF in improving its photocatalytic hydrogen production performance. Herein, this study designed and synthesized two thiadiazole-based COFs linked by imine and alkyne bonds. The results show that the photocatalytic hydrogen production performance of imine-linked COFs (TeTz–COF1) is 19.6 times higher than that of alkyne-linked COFs (TeTz–COF2). Impressively, TeTz–COF1 achieves an apparent quantum efficiency of 3.5% at 475 nm due to the presence of imine bonds. The experimental results confirm that TeTz–COF1 with imine linkages shows higher photocurrent density, lower photocurrent resistance, and longer fluorescence lifetime than TeTz–COF2 with alkyne linkages. Meanwhile, the well-defined density functional theory (DFT) calculations further suggest that both the imine bond and the acetylene bond belong to the HOMO orbitals. Particularly, the imine bonds endow TeTz–COF1 with more delocalized orbital occupation and smaller work functions, thus leading to its lower excited state energy, stronger carrier separation ability and faster electron migration capability. Both theoretical analysis and the experimental results prove that the presence of imine bonds in TeTz–COF1 can enable the efficient separation and fast transport of photogenerated carriers and high reducing ability of photogenerated electrons. This work may provide important guiding significance for the development of new COFs in the direction of photocatalytic water splitting for hydrogen production. [ABSTRACT FROM AUTHOR]

Electrochemical hydrogen production is greatly limited by the low efficiency, high cost, and poor stability of electrocatalysts. Here, we report a facile one-step method to synthesize nitrogen, phosphorus co-doped carbon encapsulated FeP/CoP derived from dual metal–organic frameworks (FeP/CoP@NPC). Thanks to the synergistic effect of its unique composition and structure, the resultant FeP/CoP@NPC shows excellent catalytic HER performance with low potentials of 198, 286, and 339 mV to achieve a current density of 10 mA cm−2 in acidic, neutral, and alkaline media along with remarkable long-time durability, respectively. More importantly, this work provides an efficient strategy for fabricating high-performance and stable pH-universal catalysts toward hydrogen generation. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenides have been the most attractive two-dimensional layered materials for electrocatalytic hydrogen evolution due to their unique structure and multi-phase electronic states. However, the enhancement of the WSe2 electrocatalytic hydrogen evolution reaction (HER) performance by bimetal co-doping has been rarely reported. Herein, the NiMo–WSe2 catalyst has been synthesized by a one-step hydrothermal reaction, with lower overpotentials of 177 and 188 mV at a current density of 10 mA cm−2 in 0.5 M H2SO4 and 1 M KOH, respectively. The large specific surface area and thinner edge morphology provide more active sites for hydrogen production, thereby significantly improving the charge transfer kinetics. Density functional theory calculation results show that under acidic conditions the ΔGH* values of NiMo–WSe2 with different structures and hydrogen adsorption sites are also different, when the hydrogen adsorption site was located at the top of the Se–Ni bond, the meta NiMo–WSe2 has a ΔGH* value (−0.04 eV) that is closest to 0. Meanwhile, NiMo–WSe2 (meta) also has a minimum of ΔGH* under alkaline conditions. DOS confirmed that Ni doping has a large impact on the electronic states at the WSe2 Fermi level, while NiMo co-doping greatly reduces the potential energy barrier of the HER reaction, jointly increasing the current density, and thus improving the HER performance. [ABSTRACT FROM AUTHOR]

Electrochemical water splitting is considered to be a promising renewable hydrogen generation technology but is significantly limited by the kinetically sluggish oxygen evolution reaction (OER) at the anode. Herein, a silver nanoparticle decorated nickel–cobalt (oxy)hydroxide composite is fabricated on nickel foam (Ag@NiCo(OH)x/NF) via electrodeposition followed by spontaneous redox reaction. Benefitting from the synergetic contributions of an amorphous/crystalline phase, abundant artificial heterointerfaces, and a 3D porous architecture, the as-designed Ag@NiCo(OH)x/NF shows substantially enhanced electrocatalytic performance toward the OER and urea oxidation reaction. Impressively, in the urea-assisted alkaline electrolyzer (coupled with commercial Pt/C on NF as the cathode) for hydrogen production, a cell voltage of only 1.49 V is required to deliver a current density of 50 mA cm−2, much lower than that of traditional water splitting (1.69 V). Importantly, this work represents a facile and feasible method to exploit efficient self-supported electrocatalysts toward overall water splitting and urea-rich wastewater purification. [ABSTRACT FROM AUTHOR]

Layered double hydroxides (LDHs) have emerged as one of the promising catalyst substitutes to noble metals in photocatalytic water splitting due to their unique optoelectronic properties. Herein, a series of novel PSO@NiFeLDH composites have been designed and synthesized to investigate photocatalytic performance. Various physicochemical techniques characterized their structural, nanomorphological, and optical properties. These results demonstrated the existence of NiFeLDH particles on the surface of PSO and the strong interaction between NiFeLDH and PSO. The photocatalytic performance was much increased in the case of PSO@NiFeLDH as compared to that of Pt-modified PSO because of the synergistic effect between PSO and NiFeLDH. Remarkably, PSO@NiFeLDH-15 exhibits the highest photocatalytic activity with a rate of 52.8 mmol h−1 g−1 at an optimal content without a Pt cocatalyst under visible light irradiation. [ABSTRACT FROM AUTHOR]

Production of hydrogen from a renewable source that is water requires the development of sustainable catalytic processes. This implies, among others, developing efficient catalytic materials from abundant and low-cost resources and investigating their performance, especially in the oxidation of water as this half-reaction is the bottleneck of the water splitting process. For this purpose, NiFe-based nanoparticles with sizes ca. 3–4 nm have been synthesized by an organometallic approach and characterized by complementary techniques (WAXS, TEM, STEM-HAADF, EDX, XPS, and ATR-FTIR). They display a Ni core and a mixed Ni–Fe oxide shell. Once deposited onto FTO electrodes, they have been assessed in the electrocatalytic oxygen evolution reaction under alkaline conditions. Three different Ni/Fe ratios (2/1, 1/1 and 1/9) have been studied in comparison with their monometallic counterparts. The Ni2Fe1 nanocatalyst displayed the lowest overpotential (320 mV at j = 10 mA cm−2) as well as excellent stability over 16 h. [ABSTRACT FROM AUTHOR]

In this work, we successfully prepared composites of carbon-modified in-phase MoC–Mo2C (MoC–Mo2C@C, MMC) nanosheets with Cd0.5Zn0.5S (ZCS) nanorods. The loading of MMC nanosheets significantly improved the hydrogen production rate of ZCS nanorods. The results showed that the photocatalytic hydrogen production rate of ZCS is the highest when MMC nanosheets are 1 wt% of ZCS nanorods (1-MMC/ZCS), reaching 68.8 mmol h−1 g−1, which is 7.7 times that of pure ZCS nanorods. The 1-MMC/ZCS photocatalyst was measured with Na2S/Na2SO3 as a hole sacrifice reagent under irradiation with 420 nm monochromatic light, and the quantum efficiency of 1-MMC/ZCS was 32.9%. The carbon layer can promote the rapid transfer of photogenerated electrons, and in-phase Mo2C–MoC as the active site can synergistically improve the photocatalytic hydrogen production rate of ZCS. Most Mo2C-based materials are still used in the field of electrocatalysis. This study provides a new idea for exploring new molybdenum-based co-catalyst materials in the field of visible light catalytic hydrogen production. [ABSTRACT FROM AUTHOR]

Electrocatalytic overall water splitting is a sustainable approach to realizing the clean production of hydrogen energy; however, it is mainly hindered by the sluggish kinetics of the oxygen evolution reaction (OER). For large-scale hydrogen production, it is great urgent to develop efficient and low-cost OER electrocatalyst candidates from commercial noble metal-based materials. Herein, a facile template method was proposed for the preparation of a series of hierarchical NiFeV hydroxide nanotubes. With the combined advantages of a hierarchical nanostructure and the synergistic effect among multi-metal elements, the ternary hydroxides delivered outstanding OER performance. In particular, a low overpotential of 256.5 mV delivering a current density of 10 mA cm−2 with a Tafel slope of 52.4 mV dec−1 was achieved by hierarchical NiFeV hydroxide nanotubes with an initial Ni/Fe/V feed ratio of 8 : 1 : 1. After a subsequent topotactic transformation, ternary phosphide (denoted as NiFeVP) was obtained with the hierarchical nanostructure well maintained, and it achieved further performance enhancement where an overpotential of only 209.5 mV was required to deliver 10 mA cm−2 with a lower Tafel slope of 30.3 mV dec−1 and excellent durability for 50 h for chronopotentiometry even at 50 mA cm−2, demonstrating an admirable OER electrocatalyst. [ABSTRACT FROM AUTHOR]

Electrocatalysts for H2 production are envisioned to play an important role in renewable energy utilization systems. Nickel-based catalysts featuring pendant amines functioning as proton relays in the second coordination sphere of the metal center have led to catalysts achieving turnover frequencies as high as 107 s−1 for H2 production. The fastest rates are observed when water is present in solution, with rates up to 103 times faster than those found in dry solvent. The focus of this paper is to provide mechanistic insight into the unexpected enhancement due to water. Addition of H2 to [Ni(PCy2NR′2)2]2+ was previously shown to give three isomers of a Ni(0) product with two protonated amines, where the N–H can be endo or exo to the Ni. By investigating the deprotonation of these two N-protonated Ni(0) intermediates resulting from the addition of H2 to [Ni(PCy2NR′2)2]2+, we observe by NMR spectroscopy studies an enhancement in the rate of deprotonation for protons positioned on the pendant amine next to the metal (endo) vs. protons that are positioned away from the metal (exo). Computational studies suggest that for smaller bases, the desolvation energy of the exogenous base is the primary contribution limiting the rate of endo deprotonation, while steric accessibility and facile proton movement also contribute. For more bulky bases, steric accessibility can play the dominant role. The significant reduction in these barriers observed in the presence of water has important implications for disfavoring less productive catalytic pathways and increasing catalytic rates. [ABSTRACT FROM AUTHOR]