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In this paper, NiCo2S4 was coated on the surface of WS2 of a 1T/2H mixed phase by a two-step hydrothermal method to form an in situ core–shell structure. The unique S-scheme heterojunction of the NiCo2S4@WS2 core–shell composite photocatalyst improved the easy recombination of carriers caused by the narrow band gap of NiCo2S4 and WS2, and improved the photocatalytic hydrogen production performance. The loading ratio of NiCo2S4@WS2, the addition of Eosin Y, and the pH value of TEOA were optimized. Under the optimal conditions, the hydrogen production rate reached 5.814 mmol g−1 h−1, which is about 8.55 times and 3.35 times the hydrogen evolution rates of NiCo2S4 and WS2, respectively. The composite catalyst exhibits excellent charge separation efficiency in photoelectrochemistry, PL and BET tests, carrier transport rate and large specific surface area that can provide more active sites, which are the main factors for the improvement of the hydrogen evolution performance. This paper demonstrates new design strategies to drive efficient photocatalytic hydrogen production by building in situ core–shell structures and optimizing the carrier transport paths, which will yield new insights. [ABSTRACT FROM AUTHOR]

Cocatalyst loading is of critical importance in efficient photocatalytic water splitting over perovskite oxynitrides. Perovskite CaTaO2N was synthesized for enhancing photocatalytic hydrogen evolution via decoration of a Pt cocatalyst by impregnation–reduction and photodeposition methods. The Pt-loaded CaTaO2N photocatalyst evolves 6.4 μmol H2 per hour, with an apparent quantum yield as high as 0.67% at a wavelength of 420 nm. Decorating the cocatalyst with uniform dispersion and intimate contact onto the surface of narrow-bandgap perovskite oxynitrides is an efficient method to upgrade photocatalytic hydrogen evolution from water splitting. [ABSTRACT FROM AUTHOR]

Covalent triazine frameworks (CTFs) containing S heteroatom are promising materials for applications in photocatalysis due to their donor–acceptor-type structures, which can improve the mobility of carriers in polymers. Herein, a series of composites (TTBT-COF@PEGx, x = 10, 20, and 30) were prepared based on CTF containing S heteroatom and polyethylene glycol (PEG) by a two-step reaction. The results show that the photocatalytic hydrogen evolution rate of TTBT-COF@PEG30 is 1.51 times that of pristine TTBT-COF. This significant improvement was attributed to PEG in the pores, which resulted in a stable layered structure, reuced distortion and deformation of the skeleton, and rapid separation and transportation of photogenerated electron holes. [ABSTRACT FROM AUTHOR]

The photocatalytic hydrogen evolution half-reaction (HER) is a promising technology for meeting future energy demands. An excellent photocarrier separation is essential for the HER. Here, a CdS/ZnS composite (CZS) with a dual photocarrier separation channel has been synthesized using the epitaxial growth method to achieve this aim. XRD and TEM show that pre-adsorption of S2− on the CdS surface facilitates the conversion of CdS into ZnS with a larger solubility product, implying a good carrier transport channel between CdS and ZnS. Based on XPS, PL, and photo-deposition experiments, a dual-channel photocarrier separation mechanism has been proposed, which is the source of the great photocarrier separation, and thus the hydrogen evolution rate of the CZS-2 sample (22.05 mmol g−1 h−1) becomes 18.5 and 73.5 times higher than those of CdS and ZnS. The apparent quantum yield (AQY) of CZS-2 at 420 nm is 4.68%. [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 development of high-performance and highly stable electrocatalysts is crucial and challenging for the hydrogen evolution reaction (HER). MOFs complexed with SnS2 can form complexes with inserted structures, and their large specific surface area and numerous pores favor mass transfer, exposing the S active sites to more SnS2, improving the utilisation of the active sites and enhancing the catalytic activity for the HER. Structural collapse can be hindered to improve the stability of the HER composites. Herein, six different kinds of SnS2 were synthesized by a hydrothermal method under discrete conditions, and SI8-SnS2 was screened out to have optimal morphology and electrocatalytic performance. Two innovative SnS2@Ni-MOF and SnS2@HKUST-1 as efficient electrocatalysts were synthesized by a facile grinding method for hydrogen generation. SnS2@Ni-MOF and SnS2@HKUST-1 catalysts showed lower overpotentials of 117 mV and 142 mV at 10 mA cm−2 (η10) and smaller Tafel slopes (58 mV dec−1 and 93 mV dec−1) than six different kinds of SnS2, Ni-MOF and HKUST-1 in 0.5 M H2SO4. Meanwhile, the Cdl values for SnS2@Ni-MOF and SnS2@HKUST-1 were estimated to be 11.5 mF cm−2 and 8.0 mF cm−2, and the stabilities of SnS2, Ni-MOF, HKUST-1, SnS2@Ni-MOF, and SnS2@HKUST-1 were tested at a current density of 10 mA cm−2. The current densities of SnS2@Ni-MOF and SnS2@HKUST-1 were stable over 8 h compared to the pure samples, and SEM, XPS tests were run after the HER test, indicating that the materials have excellent electrocatalytic stability. The syntheses of SnS2@Ni-MOF and SnS2@HKUST-1 enhance their intrinsic catalytic activity, and the porous structure promotes mass transfer efficiency, thereby improving the HER performance, which will guide the development of new and promising electrocatalysts for HER. [ABSTRACT FROM AUTHOR]

The hydrogen evolution reaction is an important process for energy storage. The six-coordinate cobalt complex [CoIII(L1−)(LH)]2+ (LH = N-(4-amino-6-(pyridin-2-yl)-1,3,5-triazin-2-yl)benzamidine) was found to catalyze photocatalytic hydrogen evolution. In this work, we performed density functional calculations to obtain the reduction potentials and the proton-transfer free energy of possible intermediates to determine the preferred pathways for proton reduction. The mechanism involves the metal-based reduction of Co(III) to Co(II) before the protonation at the amidinate N on the pyridinyl-substituted diaminotriazine benzamidinate ligand L1− to form [CoII(LH)(LH)]2+. Essentially, the subsequent electron transfer is not metal-based reduction, but rather ligand-based reduction to form [CoII(LH)(LH˙1−)]1+. Through a proton-coupled electron transfer process, the cobalt hydride [CoIIH(LH)(LH2˙)]1+ is formed as the key intermediate for hydrogen evolution. As the cobalt hydride complex is coordinatively saturated, a structural change is required when the hydride on Co is coupled with the proton on pyridine. Notably, the redox-active nature of the ligand results in the low acidity of the protonated pyridine moiety of LH2˙, which impedes its function as a proton relay. Our findings suggest that separating the proton relay fragment from the electron reservoir fragment of the redox-active ligand is preferred for fully utilizing both features in catalytic H2 evolution. [ABSTRACT FROM AUTHOR]

The development of high-efficiency and low-cost photocatalysts for hydrogen production reactions is very important to solve energy problems. In this paper we study the photocatalytic H2 evolution activity of a CeO2/CoS2 heterojunction catalyst under visible light. Characterization studies such as XRD and XPS proved the successful synthesis of a CeO2/CoS2 catalyst. The composite catalyst with a CeO2 and CoS2 mass ratio of 1 : 20 had the best activity, and the hydrogen evolution rate reached 5172.20 μmol g−1 h−1. BET and UV-Vis DRS characterization showed that the introduction of CeO2 not only increased the specific surface area of the composite catalyst, but also improved the response of the photocatalyst to visible light. In addition, PL and electrochemical experiments showed that the electrons and holes of the CeO2/CoS2 catalyst could be quickly separated and transferred, thereby accelerating the kinetics of the hydrogen evolution reaction. This work provided an experimental basis for designing a composite photocatalyst with high stability and hydrogen production activity. [ABSTRACT FROM AUTHOR]

Subphthalocyanines (SubPcs) have emerged as promising organic dyes for the development of efficient artificial photosynthetic devices, offering intense absorption in the visible region along with excellent charge transport properties. In this study, four novel SubPc derivatives containing carboxylic acid and various peripheral substituents were synthesized as a panchromatic photosensitizer to prepare an efficient and stable TiO2-based photocatalytic system for co-catalyst-free photocatalytic hydrogen evolution. To compare the influence of the nature of the peripheral substituents on photocatalytic activity, SubPc derivatives (coded as SubPc 1–4) were decorated with substituents having different electron-donating capabilities, such as alkyl thio, benzodioxin, amine, and iodo units, respectively. Photocatalytic activities were examined in the presence of TEOA as a sacrificial agent under irradiation with λ > 400 nm without co-catalyst loading. SubPc 1/TiO2 shows the best photocatalytic activity among the SubPc-sensitized photocatalysts, with a hydrogen evolution rate of 0.176 mmol h−1. While the activity of all four SubPc-based photocatalysts increased significantly after 24 h irradiation, notably, SubPc 1/TiO2 exhibited remarkable catalytic activity, achieving a hydrogen evolution rate of 6.017 mmol with a high turnover number (TON) value of 12 279 for hydrogen production. This study highlights the potential of SubPc-based sensitizers for co-catalyst-free photocatalytic H2 production and offers valuable insights into the impact of peripheral units in SubPc/TiO2-based photocatalytic systems. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C3N4), as a carbon support material with excellent stability and abundant active sites, has found widespread applications in various fields, including photocatalytic water splitting, electrolysis of water, and CO2 reduction. Presently, research on the modification of g-C3N4 primarily focuses on atomic doping, defect engineering, and the decoration of metal nanoparticles. In this study, a method involving the high-temperature pyrolysis of a solution containing thiourea and urea was successfully employed to synthesize sulfur-doped porous g-C3N4 (S-C3N4) nanosheets. Subsequently, PtCu nanoparticles were loaded onto the S-C3N4 through a hydrothermal process. In the case of Pt loading of less than half of 20% Pt/C, this catalyst exhibited a low overpotential of only 10 mV at a current density of 10 mA cm−2, which is significantly better than the 35 mV overpotential of 20% Pt/C. Furthermore, after a long period of continuous current stability testing, the overpotential of the catalyst did not increase by more than 30 mV, demonstrating excellent stability. The porous S-C3N4 nanosheets possess a large specific surface area, providing abundant active sites for the HER reaction. This research introduces a fresh method for creating innovative catalysts based on Pt alloys supported by a carbon carrier. [ABSTRACT FROM AUTHOR]

The development of photocatalysts plays a pivotal role in facilitating the production of green hydrogen energy through water splitting. In this study, one-dimensional (1D) organic–inorganic ZnCdS(EDA)/Ni@NiO (EDA: ethylenediamine) nanorods were prepared by combining organic molecules of EDA into ZnCdS. The EDA molecule possesses two amino functional groups with strong electron-donating capacity, thereby facilitating electron transfer to ZnCdS(EDA)/Ni@NiO and enabling efficient hydrogen evolution through photocatalytic water splitting. The H2 evolution rate of ZnCdS(EDA)/Ni@NiO was 159 μmol g−1 h−1 in the absence of sacrificial agents, and its H2 evolution rate in the system with EDA as the sacrificial agent can reach 5760 μmol g−1 h−1. The combination of EDA, a S vacancy, and heterojunction was proved to be the main factor for improving the separation and transfer rate of photogenerated carriers. The incorporation of ZnCdS(EDA)/Ni@NiO enhances the participation of photogenerated electrons in the photocatalytic hydrogen evolution reaction, thereby improving the overall photocatalytic activity. The synthesis of this one-dimensional composite catalyst holds great potential for advancing the development of efficient photocatalytic materials. [ABSTRACT FROM AUTHOR]

Herein, mesoporous Zn-doped g-C3N4 wrapped CdIn2S4 microsphere nanostructures were fabricated using a simple hydrothermal route. It is found that the CdIn2S4/Zn–g-C3N4 nanocomposite exhibits the most efficient photocatalytic activity for hydrogen evolution. The photocatalytic activity of the CdIn2S4/Zn–g-C3N4 composite presents the optimum performance for hydrogen evolution of 101.74 μmol h−1, which is ∼10.8 and 7.3 times that of pure g-C3N4 and bare CdIn2S4, respectively. The results of varied characterization such as TEM and XPS demonstrate that a tight heterojunction has been successfully built in CdIn2S4/Zn–g-C3N4 nanocomposites, which is highly favorable to limit the recombination of photogenerated electron–hole pairs. Furthermore, Zn could partially replace the C element in the g-C3N4 framework and enhance the separation of photo-induced electrons and holes. Moreover, the incorporation of Zn-doped g-C3N4 nanosheets with mesoporous features considerably improves the photo-stability of CdIn2S4 microspheres. We hope that these CdIn2S4/Zn–g-C3N4 nanocomposites with the tight heterojunction structure may provide new insight into designing novel photocatalysts with high efficiency and excellent stability. [ABSTRACT FROM AUTHOR]

Strengthening the separation of photogenerated charge carriers is crucial for improving the efficiency of photocatalytic hydrogen evolution. Herein, t-Mn0.5Cd0.5S/Ov-WO3 (t-MCSW) triple-phase junctions with rich oxygen vacancies were developed using the calcination-hydrothermal method. The corresponding morphology and structure of the samples were examined by XRD, TEM and XPS. The formation of the S-scheme heterostructure in t-MCSW has also been confirmed with in situ XPS, work function analysis and free radical capture tests. The experimental results demonstrate that t-MCSW-7 exhibited optimal activity (194.2 mmol g−1 h−1), which was about 4 times higher than that of the individual Mn0.5Cd0.5S (t-MCS, 48.8 mmol g−1 h−1). The apparent quantum yield of t-MCSW-7 is 29.14% at 420 nm, and the material exhibits excellent stability after seven cycles of photocatalytic reaction. The excellent photocatalytic activity of t-MCSW-7 is attributed to more efficient separation of charge carriers by triple-phase junctions connected by homojunctions and heterojunctions. Moreover, the existence of oxygen vacancies broadens absorption spectra and accelerates surface charge transfer. The synergistic effect of phase junctions and oxygen vacancies leads to an enhancement of hydrogen evolution activity. This work provides a new idea for preparing efficient photocatalysts. [ABSTRACT FROM AUTHOR]

The development of high-efficiency, precious-metal-free electrical catalysts for hydrogen evolution reactions is expected to facilitate the production of hydrolytic hydrogen fuels. Heterogeneous structures with a one-dimensional (1D) morphology exhibit efficient electrocatalytic effects owing to their abundance of active centers in the radial direction and convenient axial charge transfer in interconnected networks. Hence, a 1D MoS2/NiCoP heterogeneous junction for highly efficient hydrogen evolution performance was developed. As expected, the optimized MoS2/NiCoP/NF showed a low overpotential of 148 mV for hydrogen evolution with a current density of 10 mA cm−2 in 1.0 M KOH. Meanwhile, the developed heterogeneous structure exhibited high stability within 50 hours of continuous testing. [ABSTRACT FROM AUTHOR]

Two organic ligands, one rigid and one flexible, were designed and used to construct two cobalt-based metal–organic frameworks (MOFs) with coligands to obtain 3D and 2D structures, respectively. Both the Co-based MOFs were pyrolyzed at different temperatures to obtain the derived materials, and their electrocatalytic hydrogen evolution properties were studied. The results show that the electrocatalytic hydrogen evolution performance of MOF derivatives based on the rigid ligand was better than that of MOF derivatives based on the flexible organic ligand. [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]

Although graphite phase carbon nitride (CN) photocatalysts possess great potential in solving the global energy crisis, their photocatalytic activity is severely affected by sluggish charge dissociation/migration efficiency, a high carrier recombination rate, low active site exposure, and limited visible-light harvesting. Herein, a sulfur doped CN (x-DZCN) was tailored via one-step thermally-induced polymerization of urea with dithizone, which could evolve hydrogen at a rate of 1930 μmol g−1 h−1 (7.1 times higher than that of a single CN). The characterization of the catalyst confirmed that the boosted photocatalytic activity originated from the improved specific surface area from 46 to 61 m2 g−1, broadened visible light harvesting from 470 nm to over 600 nm, more negative conduction band (shift up of 0.54 eV), and promoted charge behavior (improved exciton dissociation and carrier migration efficiency, as well as suppressed carrier recombination capacity). The stable and efficient photocatalytic hydrogen evolution performance verifies the feasibility and potential of this photocatalyst in clean energy production. [ABSTRACT FROM AUTHOR]

A discrete liphophilic organotelluroxane macrocycle has been found to catalyse the hydrogen evolution reaction (HER) by proton reduction efficiently. The macrocycle is synthesized via chloride abstraction from bis(p-methoxyphenyl) tellurium dichloride (p-MeOC6H5)2TeCl2 (1) by silver salts AgMX4 (MX4 = BF4−, and ClO4−) resulting in in situ generated di-cationic tetraorganoditelluroxane units; two such units are held together by two weak anions μ2-MX4, bridging to form 12-membered di-cationic macrocycles [((p-MeO-C6H4)2Te)2(μ-O)(μ2-F2BF2)2]2+ (2) and [((p-MeO-C6H4)2Te)2(μ-O)(μ2-O2ClO2)2]2+ (3) stabilized via Te–(μ2-BF4/ClO4), with secondary interactions. The charge is balanced by the presence of two more anions, one above and another below the plane of the macrocycle. Similar reaction at higher temperatures leads to the formation of telluronium salts R3TeX [X = BF4− (4), ClO4− (5)] as a major product. The BF4− anion containing macrocycle and telluronium salt were monitored using 19F NMR. HRMS confirmed the structural stability of all the compounds in the solution state. The organotelluroxane macrocycle 2 has been found to act as an efficient electrocatalyst for proton reduction in an organic medium in the presence of p-toluene sulfonic acid as a protic source. [ABSTRACT FROM AUTHOR]

The improper disposal of plastic waste raises significant concerns due to its severe threat to ecosystems and public health. Artificial photosynthesis, compared with the conventional strategies (e.g., pyrolysis) operated under harsh conditions, has emerged as a green and sustainable approach to convert plastic waste into commodity chemicals under ambient conditions. In this study, we have developed a partially oxidized CuIn5S8 nanosheet photocatalyst (O-CuIn5S8) to promote the conversion of polyethylene terephthalate (PET) waste into value-added chemicals while producing hydrogen fuel. After oxygen incorporation, the as-obtained O-CuIn5S8 catalyst demonstrates significantly improved activity, with a hydrogen evolution rate of 2.57 ± 0.02 mmol g−1 h−1, which is 7 times higher than that of the pristine CuIn5S8. Furthermore, O-CuIn5S8 allows an effective transformation of pretreated PET into a range of valuable commodity chemicals, including formate, acetate, and glycolate, via a hole-induced oxidation mechanism. This work paves the way for the rational development of photocatalysts to manage plastic pollution and meanwhile reclaim the carbon source within PET plastic waste. [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 Mn0.2Cd0.8S/NiCo2S4 was prepared using an electrostatic self-assembly method. It was confirmed by analyses of the crystal structure, morphology, and elemental composition. The photoelectrochemical measurement confirmed that Mn0.2Cd0.8S and NiCo2S4 had a close interaction and can form a Schottky barrier. The construction of the Schottky junction speeded up the transport of the photogenerated electrons and inhibited the recombination of the photogenerated electrons and holes. Using Mn0.2Cd0.8S/NiCo2S4, the amount of hydrogen production was higher than with NiCo2S4 and Mn0.2Cd0.8S alone. Different amounts of NiCo2S4 were loaded onto Mn0.2Cd0.8S for the photocatalytic hydrogen production reaction. The hydrogen photocatalytic hydrogen production of Mn0.2Cd0.8S/NiCo2S4-3 was 28.97 times higher than of the Mn0.2Cd0.8S. The Mn0.2Cd0.8S/NiCo2S4 composite exhibited excellent photocatalytic activity and stability, which provided reference values for exploring bimetallic sulfide composite materials, and demonstrated great potential in photocatalytic applications. [ABSTRACT FROM AUTHOR]

Developing a rational and cost-effective approach for designing highly-efficient and sustainable electrocatalysts is essential for clean and renewable hydrogen energy. Herein, we report nitrogen-doped CoP on two-dimensional ammoniated black phosphorus (BP) nanosheets (N-CoP/NH2-BP) as novel and highly-active heterostructure electrocatalysts for the hydrogen evolution reaction (HER). Using the reactive defects on the BP nanosheets as the original sites under NH3 gas, N-doped CoP nanocrystals were grown on the surface of the BP nanosheets that were functionalized with NH2 groups at their edge. The N-CoP/NH2-BP heterostructure exhibits low overpotentials of 90 and 246 mV at 10 and 200 mA cm−2, respectively, in an alkaline electrolyte. The excellent HER activity should be attributed to the synergistic effect between N-doped CoP and NH2-functionalized BP, in which NH2-BP, with its high electron mobility and hydrophilicity, accelerates the charge transfer and offers more active sites, moreover, N-doped CoP modulates the electronic structure of CoP for enhanced HER activity. This work not only provides a novel and effective electrocatalyst, but also opens up a straightforward strategy for the design of phosphorene-based electrocatalysts for highly efficient hydrogen evolution and beyond. [ABSTRACT FROM AUTHOR]

Rational construction of low-cost, high-activity electrocatalysts is essential for hydrogen production from electrolytic water. Herein, a Co0.75Mo3S3.75/MoS2 heterogeneous interfacial structure and nitrogen and carbon co-doped on a carbon cloth hydrogen evolution electrocatalyst (NC-Co-MoS2/CC-450) was synthesized by a simple drop coating and pyrolysis method. NC-Co-MoS2/CC-450 exhibits excellent hydrogen evolution performance, achieving a current density of 10 mA cm−2 at only 56 mV, while exhibiting a Faraday efficiency of 99.85% and good stability. Moreover, at high current densities (100 mA cm−2 and 200 mA cm−2), only 155 mV and 220 mV overpotentials are required, respectively, with a small Tafel slope (69.2 mV dec−1). This is due to the intrinsic nitrogen and carbon doped multiphase composite Co0.75Mo3S3.75/MoS2 heterogeneous interface synergistic crystalline-amorphous material system, which generates a large number of lattice defects and exposes a richer active area, accelerating the efficiency of hydrogen evolution and hydrogen desorption. The hydrogen evolution performance of NC-Co-MoS2/CC-450 prepared by the rational design is significantly better than that of many previously reported molybdenum-based catalysts, and this work suggests a further way to continue the development of low-cost and efficient alkaline hydrogen evolution electrocatalysts. [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 development of new, efficient noble-metal-free photocatalysts is of great significance for the photocatalytic hydrogen evolution reaction. Herein, Co9S8 with a hollow polyhedral structure was synthesized by in situ sulfurization of ZIF-67, and subsequently, Co9S8@Ni2P composite photocatalytic materials were prepared by loading Ni2P on the surface of Co9S8 through a solvothermal method based on a morphology regulation strategy. The design of the 3D@0D spatial structure of Co9S8@Ni2P is favorable for the formation of photocatalytic hydrogen evolution active sites. Due to the excellent metal conductivity of Ni2P, Ni2P as a cocatalyst can accelerate the separation of photogenerated electrons from holes in Co9S8, thus providing a large number of available photogenerated electrons for photocatalytic reactions. It is worth mentioning that a Co–P chemical bond is formed between Co9S8 and Ni2P, which plays an active role in the transport of photogenerated electrons. The densities of states of Co9S8 and Ni2P were determined by density functional theory (DFT) calculations. The reduction of the hydrogen evolution overpotential and the formation of efficient charge-carrier transport channels on Co9S8@Ni2P were confirmed by a series of electrochemical and fluorescence tests. This study provides a new idea for the design of highly active noble-metal-free materials for the photocatalytic hydrogen evolution reaction. [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]

Green hydrogen has emerged as a promising clean energy carrier and renewable energy storage option. It has been promoted as a pivotal solution to the climate crisis and to lowering air pollution. A viable production of green hydrogen requires an efficient and durable non-precious metal electrocatalyst. In light of this, the current study describes the synthesis of an electrocatalyst consisting of Ni and N-doped graphitic carbon (Ni@NC) by a pyrolysis method under an argon atmosphere at different temperatures and the use of a cost-effective and scalable electrode platform for green hydrogen production. The electrocatalyst that was synthesized at 800 °C exhibits an overpotential of 400 mV vs. RHE at a current density of 10 mA cm−2, the Tafel slope of 110 mV decade−1, and good stability for the HER. The charge transfer resistance at the electrode–electrolyte interface is 10.8 Ω in the current study. The symbiotic effect of Ni carbon mixed with nitrogen shows excellent hydrogen evolution reaction (HER) activity. The morphology and structural properties of the electrocatalyst were well-characterized using XRD, FT-IR, Raman, FE-SEM, EDX, TEM, and XPS analysis. The Plastic Chip Electrode (PCE) enhanced the electrocatalytic activity and improved the durability issues, such as carbon corrosion in acidic conditions for the HER by the synergetic effect between the carbon electrode and a component of the catalyst. [ABSTRACT FROM AUTHOR]

Exploring low-cost and highly active photocatalysts with noble metal-free cocatalysts is of great significance for photocatalytic hydrogen evolution under simulated sunlight irradiation. In this work, a novel V-doped Ni2P nanoparticle loaded g-C3N4 nanosheet is reported as a highly efficient photocatalyst for H2 evolution under visible light irradiation. The results demonstrate that the optimized 7.8 wt% V-Ni2P/g-C3N4 photocatalyst exhibits a high hydrogen evolution rate of 271.5 μmol g−1 h−1, which is comparable to that of the 1 wt% Pt/g-C3N4 photocatalyst (279 μmol g−1 h−1), and shows favorable hydrogen evolution stability for five successive runs within 20 h. The remarkable photocatalytic hydrogen evolution performance of V-Ni2P/g-C3N4 is mainly due to the enhanced visible light absorption ability, the facilitated separation of photo-generated electron–hole pairs, the prolonged lifetime of photo-generated carriers and the fast transmission ability of electrons. [ABSTRACT FROM AUTHOR]

The application of photocatalysts for hydrogen production is limited by their low separation efficiency and poor utilization of photogenerated electron–hole pairs. To circumvent such disadvantages, the heterojunctions have been produced to improve the separation of charges and increase the activity of photocatalysts. To date, only a few studies have been conducted to investigate the interaction between the type of heterojunction interface and the photocatalytic hydrogen evolution performance of composites. Herein, the performance of an NH2-UiO-66@MoS2 composite as a photocatalyst for hydrogen production is evaluated. Moreover, NH2-UiO-66@MoS2 heterostructures were prepared through chemical bonding (C-NUM) and physical connection (P-NUM). The photocatalytic hydrogen evolution performance of NH2-UiO-66@0.2MoS2 (C-NUM-0.2) was 1.8 and 1.14 times greater than those of NH2-UiO-66 and P-NUM, respectively. The heterojunction prepared through chemical bonding facilitated the separation of the photogenerated carriers and improved the photocatalytic stability of the composite, demonstrating its potential as a high-performance photocatalyst for hydrogen production. [ABSTRACT FROM AUTHOR]

The preparation of a high-efficiency and durable electrocatalyst for the alkaline hydrogen evolution reaction (HER) is essential for realizing renewable energy technologies. Herein, a series of La0.5Sr0.5CoO3−δ perovskites with different amounts of Cu cations substituting at B-sites were fabricated for the HER. Specifically, the optimized La0.5Sr0.5Co0.8Cu0.2O3−δ (LSCCu0.2) exhibits a significantly enhanced electrocatalytic activity with an ultralow overpotential of 154 mV at 10 mA cm−2 in 1.0 M KOH, which is reduced by 125 mV compared with that of pristine La0.5Sr0.5CoO3−δ (LSC, 279 mV). It also delivers a robust durability with no obvious degradation after 150 h. Impressively, the HER activity of LSCCu0.2 is superior to that of commercial Pt/C at large current densities (>270 mA cm−2). XPS analysis indicates that Co2+ ions replaced by an appropriate amount of Cu2+ ions can increase the proportion of Co3+ and generate high content of oxygen vacancies in LSC, which leads to an increased electrochemically active surface area, thereby greatly facilitating the HER. This work offers a simple way for the rational design of cost-effective and highly efficient catalysts, which may be extended to other Co-based perovskite oxides for the alkaline HER. [ABSTRACT FROM AUTHOR]

La2Ti2O7 has been perceived as a potential photocatalytic material candidate for hydrogen evolution in recent years. However, its wide band gap brings about a narrow light absorption range and thereby results in poor photocatalytic activity. Herein, to enhance the light absorption capability, as well as promote the separation of photogenerated carriers, a CuInS2/La2Ti2O7 heterojunction photocatalyst was designed. A narrow band-gap semiconductor, CuInS2, was grown in situ on the surface of La2Ti2O7 by a solvothermal method. The effects and related mechanisms of CuInS2 loading on the photocatalytic activity were systematically investigated. The composite photocatalysts present a much better hydrogen evolution performance than the single materials. The highest hydrogen evolution rate reaches 64.41 μmol g−1 h−1. The enhancement of hydrogen evolution performance can be ascribed to the improvement of light absorption, as well as the acceleration of separation of photogenerated carriers, due to the loading of CuInS2 and the formation of a type II heterojunction between two materials. [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]

The possibility of enhancing the hydrogen evolution performance of g-C3N4 through constructing a heterojunction between g-C3N4 and metal oxides or sulfides has been exploited recently. Herein, we report the design of organic composite heterojunctions of g-C3N4 and a soluble dibenzothiophene-S,S-dioxide-containing polymer (PFSO). Constructing bulky heterojunctions by loading the soluble dibenzothiophene-S,S-dioxide-containing polymer on the surface of carbon nitride (g-C3N4) nanosheets plays a significant role in enhancing their photocatalytic activity. Benefiting from the enhanced separation of photogenerated electrons and holes as well as a broadened light-absorption range of the heterojunction design, the composite of g-C3N4/PFSO-1 containing 1 wt% PFSO shows a high hydrogen evolution rate of 149 μmol h−1, which is 30 times higher than that of bare g-C3N4. This study provides insight into fabricating high-performance polymer-heterojunction photocatalysts for H2 production. [ABSTRACT FROM AUTHOR]

At present, the electrocatalytic hydrogen evolution reaction (HER) has been widely studied in the field of energy and resource conversion. Herein, a metal-free sulfur-containing covalent organic framework material (JLNU-300) was designed and synthesized using thieno[3,2-b]thiophene-2,5-dicarboxaldehyde (TTDC) as an efficient electrocatalyst for the hydrogen evolution reaction in alkaline solution. The test analysis results showed that JLNU-300 had high crystallinity and specific surface area (298.99 m2 g−1). In addition, the material has high electrocatalytic hydrogen evolution reaction (HER) activity, with an overpotential value of 290 mV and a Tafel slope of 99 mv dec−1 at a current density of 10 mA cm−2. The introduction of thiophene groups effectively changed the electronic structure and chemical properties of the COF framework, and the high crystallinity and specific surface area of the COF itself increased the effective contact area between reactants and active points, thus promoting the HER process. The results show that the reasonable structure design of COFs can further promote their wide application in the field of electrocatalysis. [ABSTRACT FROM AUTHOR]

Herein, the synthesis in conjunction with the structural, electrochemical, and photophysical characterization of a 5,5′-bisphenanthroline (phenphen) linked heterodinuclear RuPt complex (Ru(phenphen)Pt) and its light-driven hydrogen formation activity are reported. A single crystal X-ray diffraction (SC-XRD) analysis identified a perpendicular orientation of the two directly linked 1,10-phenanthroline moieties. The disruption of π-conjugation blocks intramolecular electron transfer as evidenced by a comparative time-resolved optical spectroscopy study of Ru(phenphen)Pt and the reference complexes Ru(phenphen) and Ru(phenphen)Ru. However, reductive quenching is observed in the presence of an external electron donor such as triethylamine. Irradiating Ru(phenphen)Pt with visible light (470 nm) leads to H2 formation. We discuss a potential mechanism that mainly proceeds via Pt colloids and provide indications that initial hydrogen generation may also proceed via a molecular pathway. As previous reports on related heterodinuclear RuPt-based photocatalysts revealed purely molecular hydrogen evolution, the present work thus highlights the role of the bridging ligand in stabilizing the catalytic center and consequently determining the mechanism of light-induced hydrogen evolution in these systems. [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]

Preparing low-cost and highly efficient electrocatalysts for the hydrogen evolution reaction using a simple strategy still faces challenges. In this work, we proposed a facile phosphating process to successfully transform CoFe-BTC (BTC = 1,3,5-benzenetricarboxylate) precursors into carbon-incorporated bimetallic phosphide (CoFe-P/C) nanospheres. Due to the synergistic effect between bimetals and uniformly covered carbon shells outside, the as-synthesized porous bimetallic phosphide nanospheres exhibit superior HER activity, enhanced kinetics, and excellent cycle durability in both acidic and alkaline solutions. The optimized material could afford a current density of 10 mA cm−2 with overpotentials of 138 and 193 mV for the HER in acidic and alkaline solutions, respectively. Meanwhile, it delivered small Tafel slopes of 84 and 78 mV dec−1 for the HER in 0.5 M H2SO4 and 1.0 M KOH, respectively. Moreover, an assembled alkaline electrolyzer enabled a low voltage of 1.62 V to drive a current density of 10 mA cm−2 for overall water splitting. DFT calculations indicate that the CoP–Fe2P composite is supposed to exhibit better HER performance than each component, revealing the vital role of the interfacial site in catalyzing the HER. [ABSTRACT FROM AUTHOR]

Photocatalytic degradation of organic pollutants combined with hydrogen evolution is an effective way to solve the energy crisis and environmental problems. In this work, single s-block (IA group and IIA group) and p-block (IIIA group, IVA group and VA group) metal sites are doped into monolayer GeSe for simultaneous degradation of organic pollutants and hydrogen evolution. Se-rich growth conditions are favorable for metal atoms to substitute Ge atoms. The hydrogen adsorption free energy (ΔGH) of the Bi site on the basal planes of GeSe is −0.037 eV, which is better than those of Pt (ΔGH = −0.08 eV), Se vacancies on the GeSe edge and S vacancies on MoS2 (ΔGH = −0.06 eV). Moreover, Bi doping is superior for producing ˙OH radicals. In addition, Bi doping significantly improves the infrared (IR) light absorption ability. This work confirms the critical role of s-block and p-block metal active centers for hydrogen evolution and degradation of organic pollutants in wastewater. [ABSTRACT FROM AUTHOR]

In the application of graphitic carbon nitride photocatalytic hydrogen production, utilizing transition-metal sulfides instead of noble metals as cocatalysts has broad research prospects. Among them, nickel sulfide is favored by researchers due to its easy preparation, low cost, chemical stability, and excellent photocatalytic performance. Unfortunately, the strong sulfur–hydrogen bonds suppress its development. In this study, we successfully fabricated bimetallic CuNiSx quantum dots onto graphitic carbon nitride by the photochemical deposition method; such a small size can expose more active S sites on the edge. Simultaneously, the introduction of Cu2+ into NiSx can slightly modulate the electronic structure of Ni and S centers, thus weakening the sulfur–hydrogen bonds. Consequently, the average hydrogen evolution rate of CN/CuNiSx QDs achieved 1061 μmol h−1 g−1, which is 4.3 times than that of CN/NiSx QDs (246 μmol h−1 g−1). This research provides a new scenario to design bimetallic sulfide cocatalysts for H2 evolution. [ABSTRACT FROM AUTHOR]

As a research hotspot, 2D-MoS2 has been regarded as a low-cost substitute for platinum, and has fascinated researchers worldwide. Two crystalline phases of MoS2, i.e. the metallic octahedral 1T phase and semiconducting trigonal prismatic 2H phase, have been extensively analysed. In comparison to 2H-MoS2, the 1T phase exhibits enhanced and unique physicochemical properties. Designing a structure with two-dimensional mixed-phase MoS2, i.e. 1T/2H-MoS2 nanosheets, via phase engineering for effective charge separation and migration has received growing interest in the field of photocatalytic hydrogen generation. In this study, by varying the wt% of ammonium bicarbonate via a facile hydrothermal technique, a series of 1T/2H-MoS2 nanosheets have been fabricated. The presence of the corresponding elements, the electronic environment, phase purity, morphology and phase distinction were confirmed by Raman, XPS, XRD and HRTEM analyses. Additionally, the impedance data and the photocurrent density of the photocatalysts verify the efficient charge separation and transfer phenomenon. In accordance with the electrochemical measurements, the developed mixed-phase MoS2 nanosheets exhibit a six times greater current density than 2H-MoS2. Furthermore, the highest response of photocatalytic hydrogen production is observed with the photocatalyst with 79% 1T phase, which is about 17 times greater than that of pristine 2H-MoS2 due to the enrichment of active sites on both the edges and basal plane as well as the enhanced electronic conductivity due to the 1T phase. This study indicates that with the construction of a heterophase, i.e. 1T/2H-MoS2 nanosheets, the photocatalytic hydrogen evolution capability can be boosted, providing new insights regarding these materials. [ABSTRACT FROM AUTHOR]

Metal substrates are frequently used as current collectors and supports for electrochemically active materials, but their effect on the physical and electrochemical performance of electrocatalysts is rarely investigated. In this study, the electrodeposition method was used to coat four different metal meshes with three-dimensional nickel porous structures using hydrogen bubbles as a template. The significant influence of the metal substrates on the morphology of deposited nickel was demonstrated. 3D porous structures formed on nickel, iron, copper, and titanium meshes via the hydrogen bubble template method varied significantly. It was found that differences in the physical adsorption of hydrogen and electrochemical hydrogen evolution on metal substrates are the fundamental reasons behind the diverse morphology of the coatings. Lattice matching of the substrate and the active material also plays an important role during the electrodeposition process. Electrocatalytic performance of the newly prepared materials in water electrolysis was evaluated using the hydrogen and oxygen evolution reactions (HER and OER). The results demonstrate the high electrocatalytic activity of Ni/FeM in the OER and HER, and the good stability of Ni/TiM in HER. [ABSTRACT FROM AUTHOR]

In order to increase the effective electrochemically active area of electrocatalyst materials and improve their electrocatalytic hydrogen evolution performance, nano-porous Ni–Co alloys were prepared by rapid solidification and dealloying methods. After that, bimetallic sulfides (NiCo2S4) were formed in situ by vapor deposition, then Ru and RuS2 which have excellent intrinsic catalytic activity were adhered to the NiCo2S4 surface by a solvothermal method. Meanwhile, the Ru content was regulated to prepare the NiCo2S4/Ru electrode which was used to figure out the best component and structure for hydrogen evolution. Research shows that when the Ru content reaches 60% (wt/%), the Ru element formed a three-dimensional network flake structure and covered the NiCo2S4 surface. The active area for the reaction (Cdl = 27.6 mF cm−2) and electron transfer ability (Rct = 0.487 Ω cm−2) were increased because of the formation of the heterostructure and surface modification. At a current density of 50 mA cm−2, the NiCo2S4/Ru (60%) composite electrode possessed fast HER kinetics with a hydrogen evolution overpotential of 70 mV and a Tafel slope of 76 mV dec−1, whose electrocatalytic properties are much better than those of NiCo2S4/RuS2 with the same Ru content. The NiCo2S4/Ru (60%) catalyst exhibited superior stability with a small increase in overpotential of just 10 mV after chronopotentiometry tests for 12 h at 10 mA cm−2. [ABSTRACT FROM AUTHOR]

A dual-phase transition metal nitride (TMN) based Co4N- WNx system has been fabricated using nitridation of CoWO4. The interface between centrosymmetric Co4N and non-centrosymmetric WNx promotes charge carrier separation. This system also shows piezoelectric behavior. The piezoelectric property has been proved using piezoelectric force microscopy (PFM) measurements. In addition, modulating the noncentrosymmetric structure of Co4N- WNx allows a hydrogen production rate of about 262.7 μmol g-1 h-1 in pure water. We also show that the piezocatalytic hydrogen evolution efficiency is satisfactory. Co4N- WNx can also help achieve simultaneous piezocatalytic hydrogen production and RhB degradation. This work provides a novel strategy for designing efficient piezocatalytic materials. [ABSTRACT FROM AUTHOR]

Oxygen vacancy (VO) engineering has proved to be an effective approach for improving the hydrogen evolution reaction (HER) performance of low-cost metal oxide electrocatalysts. Cerium dioxide (CeO2), an abundant rare-earth metal oxide, is famous for its easy formation of VO and high oxygen mobility, which is believed to be conducive to its application in electrocatalytic HER. Herein, this study reports a facile modification strategy using rGO as a conductive support for CeO2 nanocrystals and introducing the transition metal Ni as the active dopant, resulting in the construction of the Ni–rGO/CeO2 electrocatalyst. It is found that rGO decoration prevents the aggregation of CeO2 NCs and increases the VO concentration in the CeO2 nanocrystals as well, while the introduced Ni leads to further formation of VO and serves as the active site for the HER reaction. Thus, the Ni–rGO/CeO2 electrocatalyst shows relatively low overpotential, a low Tafel slope, and great stability for HER, which is attributed to the synergistic effect of rGO decoration and Ni doping. This kind of facile strategy is promising for the design of noble-metal-free and low-cost electrocatalysts by the functional modification of CeO2-based nanocatalysts. [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]

A solvothermal synthesis method using Co(NO3)2 · 6H2O, thiophene dicarboxylic acid (H2tpdc), and 1,4- bis(1-imidazoly) benzene (bib) as raw materials was reported to control the growth of coordination polymers by adjusting the solvent polarity. Then, three coordination polymers with the same conformational unit and ligand and different dimensions were synthesized under three different solvent polarities. In addition, the electrochemical hydrogen evolution reaction (HER) properties of compounds 2D and 3D after high temperature pyrolysis were also investigated. The results show that compound 2D showed a better HER performance than compound 3D. We explained the reasons that compound 2D showed a better HER performance through detailed characterization. [ABSTRACT FROM AUTHOR]

The introduction of oxygen vacancies (Ov) in TiO2 has significant effects on improving the light absorption capacity, expanding the light absorption range and inhibiting photo-generated charge recombination. Here, we used hydrochloric acid and urea mixed with TiO2 hierarchical micro-nanospheres (THS) followed by annealing in an air atmosphere to dope THS with nitrogen and successfully mediated the formation of oxygen defects. Then, the Ni-based promoter is supported on the THS with oxygen vacancy defects by impregnating the metal ions in the solution. Compared with untreated Ni-THS, Ni-THS(Ov) modified by oxygen deficiency has a shorter band gap and photo-generated charge separation efficiency, and its photocatalytic water splitting capacity was also significantly improved. The hydrogen production performance of Ni-THS(Ov) (0.1 wt%) reached 4.88 mmol g−1 h−1 under full-spectrum (UV-vis) irradiation. The synergistic relationship between THS, surface oxygen vacancies and the supported Ni promoters was further investigated. [ABSTRACT FROM AUTHOR]

Electrocatalytic water splitting is an environmentally friendly method for producing hydrogen energy. To help realize the "hydrogen economy", various electrocatalysts have been prepared. Here, we propose a microwave-assisted method to synthesize a CQD-modified ZnS electrocatalyst (ZnS/C) via a one-pot approach, where L -cysteine serves as the sulfur source and carbon source. The characterization results reveal that the loading of CQDs onto ZnS nanoparticles can dramatically increase the electron mobility and active area, playing a fundamental role in obtaining superior HER catalytic performance. Consequently, the as-prepared ZnS/C requires a low overpotential of only 126 mV to achieve a current density of 100 mA cm−2, and it has a low Tafel slope of 28.98 mV dec−1. Moreover, this study not only provides a high-efficiency and potential electrocatalyst for H2 evolution, but is also expected to provide a new design scheme for using CQDs as a cocatalyst to promote charge transfer in nanocomposites. [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]