Search

Semiconductor photocatalysis is a potential solution to meet energy needs with green and inexhaustible solar energy. However, designing efficient and stable photocatalysts is a challenging task due to the limited ability to effectively separate electrons and holes. In this paper, by using a straightforward ethanol dispersion technique, we were able to combine ultrathin layered Cu-TCPP MOFs with g-C3N4 nanosheets, resulting in the creation of an extremely effective nano-composite photocatalyst with exceptional UV-vis activity. CT/CN heterojunctions displayed remarkable photocatalytic efficacy for the production of H2, with 3CT/CN showcasing a five-fold enhancement in photoactivity as compared to the unadorned g-C3N4. Based on the results of photoluminescence spectroscopy, electrochemical impedance spectroscopy, and electrochemical reduction, the considerably improved charge transfer and separation, together with the possible catalytic capability of uniformly distributed metal nodes in Cu-TCPP, are believed to be the underlying reason for the observed exceptional photoactivity. After thorough analysis, a potential process for charge transfer and segregation between g-C3N4 and Cu-TCPP has been suggested. [ABSTRACT FROM AUTHOR]

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]

Cocatalysts are usually applied in the photocatalytic water splitting process to accelerate the kinetics of the hydrogen evolution reaction (HER). Specifically, the transition metal nitride (Mo2N) featuring a unique local surface plasmon resonance (LSPR) effect has exhibited great potential to function as a HER cocatalyst. However, the low metallicity of Mo2N hampers its ability to improve charge separation. To address this issue, transition metal atom doping (Co and Cu) engineering was used to modulate the electronic structure of Mo2N nanosheets to achieve a higher electrical conductivity and a lower hydrogen adsorption free energy (‖ΔGH*‖), thereby favoring the HER kinetics. Density functional theory (DFT) calculations and experimental results showed that Co-doping and Cu-doping mainly take place at Mo sites in the crystal structure of Mo2N to form stable structures of Co doped Mo2N (Co–Mo2N) and Cu doped Mo2N (Cu–Mo2N). Compared with pristine Mo2N, both Cu–Mo2N and Co–Mo2N demonstrated a much improved cocatalytic effect over g-C3N4 in promoting charge separation, accelerating HER kinetics and enhancing light absorption. The Co–Mo2N with the highest conductivity and lowest ‖ΔGH*‖ illustrated the best cocatalytic effect, and the H2 production performance (367.8 μmol g−1 h−1) of Co–Mo2N/g-C3N4 achieved was 10 and 5 times higher than those of Mo2N/g-C3N4 and Cu–Mo2N/g-C3N4. This paper provides significant guidance in the design and development of efficient cocatalysts for the HER application. [ABSTRACT FROM AUTHOR]

Element doping and construction of heterojunction composites are the most common ways to enhance g-C3N4, which are very attractive in achieving high photocatalytic activity. In this study, 2D nanosheet structured BCN was obtained by doping B atoms with graphite carbon nitride. Subsequently, Ti MOFs were loaded on BCN to obtain a Z-scheme heterojunction composite TBCN through calcination. Under simulated sunlight, the photocatalytic hydrogen production rate of the TBCN heterostructure was 1242 μmol h−1 g−1, which was 2.2 times higher than that of BCN and 9.34 times higher than that of bulk graphite carbon nitride (GCN). Experimental results showed that the construction of a Z-scheme heterojunction composite (TBCN) could effectively adjust the material band gap position, expand the light absorption range, enhance electron transfer and inhibit electron–hole recombination, which are crucial for efficient photocatalysis. This study not only provides a strategy for constructing heterojunction composites in the field of g-C3N4 photocatalytic hydrogen evolution, but also deeply analyzes the electron migration direction and the reasons for enhancing carrier separation in the Z-type heterojunction scheme, thus providing potential guidance for future research. [ABSTRACT FROM AUTHOR]

In this paper, a novel pristine carbon nitride (np-CN) with hollow capsule-like morphology was facilely prepared by the thermal polymerization of melamine and cyanuric chloride at 550 1C in air for 4 h. Then, modified carbon nitride (CN-P4mg) micro-flakes with zigzag edges were synthesized by the copolymerization of melamine, cyanuric chloride, and triaminotriphenylamine with a mass fraction of 0.13%. Analysis of the microstructure, surface state, porosity, and optoelectronic properties of the two samples indicates that CN-P4mg has a larger specific surface area and a lower bandgap than np-CN. Under visible light, CN-P4mg displays enhanced photocatalytic performance for the generation of hydrogen compared to that of np-CN and bulk graphite carbon nitride (g-C3N4). The photocatalytic hydrogen evolution rate of CN-P4mg reaches 16897.3 mmol g-1 h-1, which is 1.84 times that of np-CN and 72 times that of bulk g-C3N4. The experimental results confirm that the addition of triaminotriphenylamine provides a modified design for developing metal-free carbon nitride derivatives and a new route to study efficient photocatalytic materials. [ABSTRACT FROM AUTHOR]

Exploring efficient non-noble metal catalysts for the hydrogen evolution reaction (HER) will contribute to the development of clean and green energy technologies. Herein, we adopted a "waste utilization" strategy by using readily available and inexpensive coconut shell waste as a carbon source to synthesize carbon materials anchored with a Cu7Co alloy (Cu7Co/C) as a potential electrocatalyst for the hydrogen evolution reaction (HER). Utilizing a combination of hydrothermal and pyrolysis methods, the synthesized Cu7Co/C catalyst showcases superior HER electrocatalytic performance in alkaline solutions, with an overpotential of 134 mV at 10 mA cm−2 and a Tafel slope of 94 mV dec−1. The alloying of Cu and Co within Cu7Co/C markedly improves charge transfer capabilities, enhancing HER electrocatalysis. This research underscores the exceptional catalytic performance and stability of Cu7Co/C nanocomposites in alkaline media for the HER, attributed to a synergistic effect between the carbon derived from coconut shells and the bimetallic Cu7Co alloy. [ABSTRACT FROM AUTHOR]

In this work, CoV-LDH/ZnIn2S4 (CoV-LDH/ZIS) nanocomposites were synthesized through a self-assembly process in order to investigate the influence of CoV-LDH addition on the rate of hydrogen production. XRD and TEM measurements confirmed the effective preparation of CoV-LDH/ZIS nanocomposites. Among all the nanocomposite photocatalysts, 2.0%-CoV-LDH/ZIS showed the best photocatalytic performance with a hydrogen production rate of 1397.3 μmol g−1 h−1, approximately 2.2 times that of pure ZnIn2S4 (ZIS). The X-ray photoelectron spectroscopy (XPS) measurement indicated that there is a strong interfacial interaction between ZIS and CoV-LDH, indicating that more than simple mechanical mixing had occurred. The steady-state fluorescence spectroscopy (PL) and time-resolved photoluminescence (TRPL) spectroscopy results showed that the electron and hole recombination in CoV-LDH/ZIS is significantly reduced and that efficient interface charge transfer and separation are achieved. This work sheds light on the interfacial electron transfer between two semiconductor materials, which promotes the separation of photogenerated carriers and thus enhances photocatalytic hydrogen production activity. [ABSTRACT FROM AUTHOR]

Finding efficient photocatalysts is the key to achieving sustainable hydrogen production. In this work, a rational design of Cd2+-doped Zn3In2S6 (ZIS) and a heterojunction structure with g-C3N4 (GCN) was carried out to form a GCN/Cd/ZIS composite. The synergistic effect of Cd2+ doping and heterojunction construction in the photocatalytic hydrogen production process was probed. The results showed that doping Cd2+ modified the bandgap structure of ZIS and improved the photocatalytic activity. The heterojunction construction between Cd/ZIS and GCN also effectively promoted the separation and migration of photogenerated carriers, which significantly improved the hydrogen production performance of the GCN/Cd/ZIS composite. The hydrogen production rate of 15% Cd/ZIS and 5% GCN/Cd/ZIS was 2.45 mmol g−1 h−1, 3.34 mmol g−1 h−1, which was 4.3 and 5.9 times higher than that of ZIS (0.57 mmol g−1 h−1), respectively. This study provides strong evidence that doping and heterojunction construction can synergistically improve photocatalytic activity. [ABSTRACT FROM AUTHOR]

Hydrazine borane (HB) has been considered to be an excellent medium for hydrogen storage, but the development of efficient catalysts for controllable and complete hydrolytic dehydrogenation of HB remains a severe challenge. In this study, a novel catalyst consisting of Ni0.6Pt0.4 nanoparticles supported on phosphorus-doped reduced graphene oxide (P-rGO) is readily obtained via a simple co-reduction method and serves as a highly efficient and stable catalyst toward the complete hydrolytic dehydrogenation of HB. Compared with Ni0.6Pt0.4/rGO, the as-prepared Ni0.6Pt0.4/P-rGO catalyst exhibits much higher catalytic activity for HB dehydrogenation, providing a total turnover frequency (TOF) value of 2419.4 h−1 at 323 K, which surpasses that of the majority of reported catalysts. Meanwhile, it also exhibits lower activation energy (Ea) and better recycle stability. The reason for the outstanding catalytic performance of Ni0.6Pt0.4/P-rGO could be attributed to the combined influence of small particle sizes, the enhanced synergistic effects of NiPt nanoparticles and the P-rGO substrate, the electronic interaction between Ni and Pt, and the NaOH promotion effect. This work provides an innovative approach to construct highly efficient and robust catalyst systems using simple and controllable methods. [ABSTRACT FROM AUTHOR]

This study developed an efficient photocatalyst for hydrogen production, consisting of CdS nanorods and the CoTPPBr4 co-catalyst. The synthesized photocatalyst was characterized using a suite of techniques including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), photoluminescence (PL) spectroscopy, and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS). Additionally, transient photocurrent response and electrochemical impedance spectroscopy (EIS) were carried out to further probe the material's properties. Our findings demonstrate that the CoTPPBr4 co-catalyst significantly enhances the photocatalytic H2 evolution efficiency under visible light irradiation. Notably, among the tested photocatalysts, a 12.5% CoTPPBr4/CdS composite exhibited the most superior photocatalytic performance, achieving a hydrogen production rate of 41.3 mmol g−1 h−1, which is 4.1 times higher than that of pristine CdS. The introduction of CoTPPBr4 effectively facilitates charge transfer within CdS, enhances the separation efficiency of light-induced electron–hole pairs, and boosts the surface H2-evolution kinetics. This research not only introduces a promising photocatalyst for visible light-driven hydrogen production but also provides a way for the development of highly efficient and stable CdS-based hybrid semiconductor nanocomposites suitable for diverse photocatalytic applications. [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]

In the photocatalytic processes of ferroelectric semiconductor materials, how to induce a depolarized electric field (Edp) by polarization to reduce the electron–hole recombination rate is still a big problem. Here, the ABO3-type K0.5Na0.5NbO3 (KNN) material is modified by Nd and Ni elements at A/B sites to narrow the band gap and maintain the room-temperature ferroelectric behavior. The 0.96KNN–0.04NdNiO3 sample shows the narrowed band gap (∼2.75 eV) and high residual polarization value (∼11.56 μC cm−2). After high-field poling, the hydrogen production rate of the sample in the full spectrum reaches 926.28 μmol g−1 h−1, indicating an increase of approximately 5 times compared to the 170.45 μmol g−1 h−1 of the unpoled sample. The improved performance of photocatalytic hydrogen production mainly results from the reduction of band gap and the formation of Edp after polarization. The change in the position of the top of the valence band after sample polarization reveals that high-field poling can improve charge transport efficiency by energy band bending. [ABSTRACT FROM AUTHOR]

Developing novel catalysts with excellent photocatalytic hydrogen evolution activity is crucial for expediting current research on solar-chemical energy conversion. In the present study, unique Sn3O4/CdS composites were carefully designed and prepared using a facile hydrothermal method to achieve outstanding photocatalytic H2 production activity. Various techniques were employed to determine the crystalline structure, chemical composition, microstructure, and optical and electrochemical characteristics of the prepared samples. The experimental results indicate that zero-dimensional (0D) CdS quantum dots were tightly attached to the surface of three-dimensional (3D) Sn3O4 nanoflowers. Furthermore, enhanced light-absorbing capacity and accelerated electron–hole separation and transfer were achieved after incorporating CdS quantum dots into Sn3O4 nanoflowers. The generation rate of hydrogen using the optimal sample (Sn3O4/CdS QDs-2) was about 20.74 μmol g−1 h−1, which was 2.86 and 3.16 times those of pure Sn3O4 and CdS, respectively. In addition, the possible photocatalytic H2 production mechanism of Sn3O4/CdS nanocomposites was also revealed. This work is highly desirable to provide valuable inspiration for rational design and preparation of efficient photocatalysts for H2 evolution. [ABSTRACT FROM AUTHOR]

In the present work, a ternary composite MoS2/soluble g-C3N4/CdS was synthesized using a facile one-pot hydrothermal reaction and conventional reflux reaction method. The composition, morphology, and properties of the ternary composite were characterized. The photocatalytic performance of the ternary composite was evaluated for hydrogen generation under LED lamp irradiation (450 nm < λ < 465 nm) with lactic acid (LA) used as a sacrificial reagent. The results demonstrated that the maximum hydrogen production reached 4869.6 μmol under the optimal hydrogen production conditions, including a composition of 20% soluble g-C3N4, 9% MoS2, a solution pH of 1, and an irradiation time of 6 hours. The corresponding hydrogen production rate for the ternary composite was calculated to be 8116 μmol g−1 h−1. Furthermore, a possible electron transfer mechanism of the ternary composite system was briefly explored. The interaction and synergistic effects between MoS2, soluble g-C3N4, and CdS in the ternary composite likely facilitate efficient electron transfer, resulting in enhanced photocatalytic activity for hydrogen production. Mechanistic research showed that the electron transfer pathway represented either a double or single type II heterojunction photocatalytic system. [ABSTRACT FROM AUTHOR]

The development of non-noble metal catalysts that exhibit high performance in the dehydrogenation of ammonia borane has been considered a safe and efficient method for hydrogen generation. In this study, a series of CuxCoy alloy nanoparticles with different ratios were highly dispersed on a core–shell microsphere carrier, and the carrier was prepared using carbon spheres as a template. The catalytic activity for H2 from ammonia borane (NH3BH3, AB) hydrolysis was investigated by adjusting the ratio of Cu2+ to Co2+ doping in the catalyst. The Co1Cu1/C@Cu0.76Co2.24O4 core–shell heterostructure catalyst shows excellent catalytic activity with a high turnover frequency (TOF) value of 82.58 molH2 molcat−1 min−1 and a low activation energy (Ea) of 16.06 kJ mol−1. Detailed analysis indicates that the outstanding activity of AB for hydrolytic dehydrogenation could be attributed to the unique core–shell hetero-structures and high dispersion of the CuCo alloy nanoparticles. [ABSTRACT FROM AUTHOR]

Elemental doping is an effective and attractive method for improving the photocatalytic performance. Here we synthesized three types of O-doped carbon nitride nanofibers (ACN, CCN, and LCN) through a one-pot simple solvothermal process by using L -arginine, L -cysteine and L -lysine as O dopants into pristine carbon nitride nanofibers (CNF). The three O-doped samples exhibited enhanced light harvesting capacity and satisfactory O2 adsorption and activation ability, which is beneficial for the following H2O2 generation process. The photocatalytic H2O2 generation rates of the optimal ACN, CCN, and LCN samples are 156.9, 166.2 and 107.2 μmol g−1 h−1, which are higher than that of pristine CNF (72.3 μmol g−1 h−1). Especially, CCN shows an apparent quantum efficiency of 4.66% at 420 nm. The results of photocurrent measurements and photoluminescence spectra indicate that the charge carrier recombination was effectively inhibited in the O-doped samples. Our research provides an effective and environmentally friendly strategy to improve the H2O2 generation performance by using common compounds in human life. [ABSTRACT FROM AUTHOR]

The combustion of fossil fuels has brought about serious energy shortages and environmental pollution issues. This study involves the development of green and environment-friendly nonprecious metal photocatalysts with high hydrogen production performance. Hence, a series of CoxSy/Mn0.5Cd0.5S composites was prepared through a simple hydrothermal process. When the loading amount of amorphous CoxSy was 3 wt%, the CoxSy/Mn0.5Cd0.5S composite catalyst showed the best photocatalytic activity under visible light irradiation (λ > 420 nm), giving a hydrogen production rate of 5677.6 µmol g−1 h−1, which is 121.6 times that of pure CdS and 4.8 times that of Mn0.5Cd0.5S. Moreover, the 3 wt%-CoxSy/Mn0.5Cd0.5S catalyst exhibited good photostability. The experimental results demonstrate that the construction of the CoxSy/Mn0.5Cd0.5S heterojunction effectively facilitates the separation of charge carriers, resulting in an enhanced photocatalytic activity. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) have great potential for producing photoelectrocatalyzed hydrogen and degrading pollutants, owing to several factors such as high porosity and tunable semiconductor-like properties. Wide band gaps, which restrict their use to only UV light induced reactions, and low efficiencies for the separation of photogenerated charge carriers (electrons and holes) pose significant challenges to the widespread applications of MOFs. In this study, a hierarchical hollow Pt@H-UiO-66-NH2/CdS ternary catalyst was designed and synthesized. The immobilized CdS nanoparticles (NPs) in this catalyst endow the MOF H-UiO-66-NH2 with high visible light absorption ability and the Pt NPs serve as electron sinks to improve charge carrier separation. Furthermore, the hierarchical hollow structure of H-UiO-66-NH2 in the composite contributes to boosting light absorption and shortening the distance for charge transfer. As a proof of principle, Pt@H-UiO-66-NH2/CdS catalyzes methylene blue (MB) degradation with a high rate constant of 1.025 × 10−2 and hydrogen production with a rate of 12 810 μmol g−1 h−1, the latter of which is about 2.3, 11.7 and 173 times higher than those of Pt@UiO-66-NH2/CdS, H-UiO-66-NH2/CdS and Pt@H-UiO-66-NH2, respectively. [ABSTRACT FROM AUTHOR]

C/Ti3C2/g-C3N4 hollow microspheres (HM) were prepared by the template method to construct Ti3C2/g-C3N4 Schottky junctions on the spherical surface. The C/Ti3C2/g-C3N4 HM Schottky junctions presented excellent photocatalytic properties for producing hydrogen and decomposing organic pollutants simultaneously from wastewater without the addition of a sacrifice agent. The research revealed that the built-in electric field between g-C3N4 and Ti3C2 MXene could decrease the charge transfer resistance, leading to efficient photo charge separation, and the organic pollutant tetracycline (TC) could act as a sacrifice agent for splitting water. The H2 evolution rate of the CN-TCM-3 sample in deionized water with a sacrifice agent reached 105.4 μmol g−1 h−1, and the TC removal rate reached 100% within 120 min. The hydrogen production efficiency of CN-TCM-3 in the natural water of Slender West Lake without or with TC as a sacrifice agent was 2.3 μmol g−1 h−1 and 3.2 μmol g−1 h−1, respectively. The addition of TC improved the hydrogen production efficiency by 39%. This research indicated that the C/Ti3C2/g-C3N4 HM Schottky junctions could be a potential photocatalyst for producing hydrogen and decomposing organic pollutants in sewage simultaneously. [ABSTRACT FROM AUTHOR]

Solar-driven photocatalytic hydrogen generation via splitting water requires an efficient visible light active photocatalyst. In this work, Ni cocatalysts on a TiO2 composite photocatalyst with different graphene oxide (GO) contents were prepared using a hydrothermal method and characterized by TEM, XRD, UV-vis, Raman and PL spectra. The results show that the synthesized TiO2/GO/Ni nanosheet composites have a large specific surface area and can provide a large number of active sites for a photocatalytic hydrogen production reaction. GO can broaden the optical absorption range of TiO2 and absorb more visible light, thus stimulating more photogenerated electron–hole pairs. At the same time, GO can collect electrons and promote the separation of photogenerated electron–hole pairs. Ni, as a cocatalyst, can be used as an active site for hydrogen ion adsorption, which is conducive to promoting the migration of photogenerated electrons in the system and prolonging the life of photogenerated electrons and holes, thus ensuring the high efficiency of the photocatalytic reaction. [ABSTRACT FROM AUTHOR]

Silicon (Si) is a commercially available semiconductor used for photoelectrochemical (PEC) hydrogen production, which has various advantages of earth-abundant element, non-toxicity, broad absorption of the solar spectrum, high saturation current and industrial applicability. However, it suffers from surface light reflection, short carrier-transport distance, slow charge transfer at the electrode–electrolyte interface, and poor stability in aqueous electrolytes, resulting in decreased photocurrent density and elevated overpotential. In this work, a surface-modified nanoporous Si photocathode, called black Si (b-Si), was fabricated with a large electrochemical surface area for loading of Co(dmgH)2(py)Cl catalyst. Under the illumination of simulated sunlight, the optimal b-Si/[Co] photocathode exhibited a high photocurrent density of −4.15 mA cm−2 (0 VRHE), a value 319 times that of the f-Si electrode under the same conditions. Moreover, the onset potential positively shifted to 0.31 VRHE and the driving force required for H2 production was significantly decreased. The enhanced water splitting was attributed to the rapid transfer of charge across the electrode–electrolyte interface and efficient HER reactivity via the [Co] molecular catalyst. The surface engineering of the nanoporous structure and the deposition of molecular catalyst on the Si electrode have provided insights into the construction of semiconductor/catalyst hybrid photoelectrodes, and were concluded to synchronously improve the charge transfer at the electrode/electrolyte interface, reduce the overpotential, and speed up the PEC water splitting. [ABSTRACT FROM AUTHOR]

ZnIn2S4 is considered one of most promising green catalysts for visible light driven photocatalytic H2 generation, but it suffers from relatively low photocatalytic performance. Here, we for the first time report the design and preparation of an efficient ZnIn2S4-based catalyst using porous ZnWO4 as cocatalyst (denoted ZIS/PZW). ZIS/PZW consists of flower-like microspheres composed of ZnIn2S4 nanosheets embedded with porous ZnWO4 nanoflakelets. The as-synthesized ZIS/PZW showed excellent photocatalytic performance for H2 generation with an optimal hydrogen production rate of 8.86 mmol g−1 h−1. Further investigation revealed that the porous ZnWO4 cocatalyst could lead to the formation of dense contact sites with ZnIn2S4 nanosheets, thus benefiting electron migration. The hydrogen generation rate was found to be 2.15 times higher than that when solid ZnWO4 nanoparticles acted as cocatalyst. Our work highlights the importance of finely designing cocatalysts and provides a new route for the further development of high-efficiency ZnIn2S4-based photocatalysts for H2 generation. [ABSTRACT FROM AUTHOR]

Developing economic, earth-abundant metal-based hydrogen evolution reaction (HER) electrocatalysts with high-performance is a matter of great significance. Transition metal phosphides have attracted special attention and are considered as remarkable HER electrocatalysts. Here, we have successfully synthesized a bimetallic phosphide electrocatalyst (MoP/MoNiP@NC) via a one-step calcination and simultaneous phosphating process. The corresponding precursor is self-assembled through electrostatic and coordination interactions among polyoxometalate (Mo40), nickel ions and polypyrrole. MoP/MoNiP@NC shows splendid electrocatalytic activity with overpotentials of 125 and 144 mV at 10 mA cm−2, and excellent electrochemical stability in acid–alkaline media compared to other reported TMPs. The superior hydrogen generation performance can be mainly assigned to the protection effect by a porous conductive carbon layer structure and the synergistic effect of multiple species in MoP/MoNiP@NC. This study provides an operational and easy approach to synthesize earth-abundant metal-based phosphide electrocatalysts for water decomposition. [ABSTRACT FROM AUTHOR]

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

Cocatalysts are usually applied in the photocatalytic water splitting process to accelerate the kinetics of the hydrogen evolution reaction (HER). Specifically, the transition metal nitride (Mo2N) featuring a unique local surface plasmon resonance (LSPR) effect has exhibited great potential to function as a HER cocatalyst. However, the low metallicity of Mo2N hampers its ability to improve charge separation. To address this issue, transition metal atom doping (Co and Cu) engineering was used to modulate the electronic structure of Mo2N nanosheets to achieve a higher electrical conductivity and a lower hydrogen adsorption free energy (‖ΔGH*‖), thereby favoring the HER kinetics. Density functional theory (DFT) calculations and experimental results showed that Co-doping and Cu-doping mainly take place at Mo sites in the crystal structure of Mo2N to form stable structures of Co doped Mo2N (Co–Mo2N) and Cu doped Mo2N (Cu–Mo2N). Compared with pristine Mo2N, both Cu–Mo2N and Co–Mo2N demonstrated a much improved cocatalytic effect over g-C3N4 in promoting charge separation, accelerating HER kinetics and enhancing light absorption. The Co–Mo2N with the highest conductivity and lowest ‖ΔGH*‖ illustrated the best cocatalytic effect, and the H2 production performance (367.8 μmol g−1 h−1) of Co–Mo2N/g-C3N4 achieved was 10 and 5 times higher than those of Mo2N/g-C3N4 and Cu–Mo2N/g-C3N4. This paper provides significant guidance in the design and development of efficient cocatalysts for the HER application. [ABSTRACT FROM AUTHOR]

Photocatalysis is one of the most promising methods to solve the problems of solar energy conversion and sustainable fuel production. Among them, the semiconductor electronic transition to produce hydrogen is the most critical research topic in the field of photocatalysis. ZnS and Ag2Mo2O7 monomers were prepared by the hydrothermal method. The S-scheme heterojunction was formed by electrostatic adsorption of the two materials. The S-scheme heterojunction can improve the separation rate of photogenerated carriers through the built-in electric field so that the hydrogen production rate of the system can reach a maximum of 871.9 μmol g−1 h−1. The system showed a good photoelectric response according to UV-Vis DRS and electrochemistry studies and excellent hydrogen evolution performance. In this study a DFT simulation of the heterojunction interface formed by the system was also carried out, and the relative size of the surface work function indicated the transfer direction and path of electrons. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C3N4), possessing high thermal and chemical stability, non-toxicity, facile synthesis, and low band gap energy is a promising candidate for photocatalytic applications. In this study, bulk and exfoliated g-C3N4 were synthesised from different precursors (melamine and urea). Moreover, the surface of bulk g-C3N4 and exfoliated g-C3N4 was modified with graphene (0.5 wt% and 1 wt%) aiming to obtain a prolonged carrier lifetime. The effect of g-C3N4 synthesis from various precursors and the influence of graphene content on the photocatalytic activity during the degradation of a water–methanol mixture under UVC irradiation were examined, in comparison to commercial P25. Hydrogen, methane and carbon monoxide were the decomposition products; hydrogen was the main product of decomposition, whereas CH4 and CO resulting from the reduction of CO2 were generated in a significantly smaller amount. All the produced photocatalysts, whether pure or modified with graphene, exhibited higher activity than the commercial photocatalyst P25. [ABSTRACT FROM AUTHOR]

A facile solvothermal assisted g-C3N4 post-grafting technique with aromatic amine dyes via a Schiff base chemical reaction was successfully developed in this study. Based on this strategy, three D–π–A type aromatic amine organic dyes (TPA-CNCHO, PTZ-CNCHO, and CZ-CNCHO) were covalently grafted onto g-C3N4. The resulting composite photocatalyst was characterized using TEM, XPS, FT-IR, UV-Vis DRS, PL, and transient photocurrents, which confirmed the feasibility of the modification strategy. The values for the photocatalytic hydrogen production rates obtained for g-C3N4/TPA-CNCHO, g-C3N4/PTZ-CNCHO, and g-C3N4/CZ-CNCHO were 16232.7, 13266.9, and 11822.8 μmol h−1 g−1 respectively. Each of these values is 40, 33, and 29 times higher than that of pure g-C3N4, respectively. Among them, g-C3N4/TPA-CNCHO exhibited the highest photocatalytic hydrogen-production activity and the highest recycling usage stability. In addition, a possible mechanism for the separation and transfer of photo-induced carriers was obtained based on DFT calculations and experimental results. This further confirmed that covalently post-grafting g-C3N4 with organic aromatic amine dyes through a Schiff base reaction was useful and could effectively enhance the photocatalytic hydrogen evolution reaction. This is a general facile solvothermal method because it can be used for the grafting of other types of functional aromatic organic dyes onto g-C3N4. [ABSTRACT FROM AUTHOR]

Commercial applications of electrolytic water splitting require cost-efficient and active oxygen evolution catalysts. Nickel–iron (NiFe)-based compounds have attracted significant attention as oxygen evolution reaction (OER) catalysts due to their high catalytic activity. We develop a simple and easily controlled method by combining anodic fluoridation and cyclic voltammetry (CV) treatment to convert NiFe alloy to Ni/Fe hydroxide. A cracked layer structure of Ni/Fe hydroxide formed on the surface during the fluoridation of NiFe alloy and the CV process in KOH. The Ni/Fe hydroxide exhibits considerable OER activity with an onset potential of 1.47 V vs. RHE and a Tafel slope of 47 mV dec−1 in 0.1 M KOH. The electrode also shows an acceptable stability in alkaline media. The results indicate that anodic fluoridation and CV treatment are promising methods to form active layer structures of hydroxide on transition metals and their alloys, further increasing the electrocatalytic activity of the catalyst. [ABSTRACT FROM AUTHOR]

The MgH2–LiH composites with different composition ratios were prepared by different ball milling times, and the hydrogen generation performances of the composites were investigated and compared. X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy techniques were adopted to elucidate the performance improvement mechanisms. The results show that the hydrogen generation yield and kinetics can be improved with the increase of LiH content significantly. For the 7MgH2–3LiH and 1MgH2–1LiH, with the increase of the ball milling time, the hydrogen yield increases firstly, and then decreases, but the kinetics almost do not change. This may be caused by the change of particle size of the composites after ball milling. However, for the 9MgH2–1LiH, the hydrogen yield increases with ball milling time but the kinetics decrease gradually. This may be due to the gradual movement of LiH from the surface to the interior of MgH2 and to the covering of MgH2 after ball milling. [ABSTRACT FROM AUTHOR]

The study of environmentally friendly semiconductor photocatalysts has important practical significance for efficient photocatalytic hydrogen evolution. In this experiment, type II heterojunction NiCo-LDH/CeO2 was prepared by in situ loading, and the NiCo-LDH/CeO2 catalyst showed good activity under simulated sunlight irradiation. Under simulated visible light irradiation, its hydrogen production rate reached 2.7 mmol h−1 g−1, which was higher than that of NiCo-LDH (0.86 mmol h−1 g−1). Through a series of characterization data, it can be concluded that the heterojunction successfully constructed by the close contact between NiCo-LDH and CeO2 accelerates the separation of photogenerated electrons and holes and can effectively inhibit the recombination of the two so that more electrons are involved in the hydrogen evolution reaction. The material has good interfacial charge transfer performance, which improves the photocatalytic performance. This work can provide an effective method for the research and development of NiCo-LDH. [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]

Developing economic and high-performance noble metal-free photocatalysts is the key to realize efficient photocatalysis. In this work, NiS nanoparticles and hierarchical Sn3O4 nanostructures are tightly bonded by a two-step method combining hydrothermal and ion precipitation to construct a 0D/3D nanocomposite structure, which accelerates the interface electron transfer rate and photogenerated electron–hole separation efficiency. Compared with the pure Sn3O4, the loaded samples obviously have stronger light absorption capacity and effectively improve the utilization of visible light, thus showing enhanced photocatalytic hydrogen generation performance. NiS provides more active sites on the surface and facilitates electron transit as an electron acceptor, resulting in increased photocatalytic activity. As a result, when the loading of NiS reaches 1.0%, the photocatalyst shows an excellent hydrogen production performance, with an average hydrogen generation rate of 17.43 μmol g−1 h−1, which is 2.4 times than that of the pristine Sn3O4. This research offers a new idea to develop noble metal-free photocatalysts with high activity. [ABSTRACT FROM AUTHOR]

A synthesized non-precious metal-free electrocatalyst is demonstrated using the hydrazine hydrate oxidation reaction as a model reaction of hydrogen production. The C60 nanocomposite functionalized with ethylenediamine (EDA@C60) was fabricated using a simple chemical approach. The EDA@C60 composites were characterized using field emission scanning electron microscopy, energy dispersive analysis of X-rays, Fourier-transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, and electrochemical techniques. In this study, the nitrogen lone pairs from the ethylenediamine surface-functionalized on C60 are responsible for the further enhancement of electrocatalytic activity towards the hydrazine oxidation reaction. Comparative electrochemical studies with acid-treated C60, i.e., O–C60, and the further-functionalized ethylenediamine catalysts (EDA@C60) demonstrated high performance, which was ascribed to their inferior onset potential and better stability. The electrochemical measurements indicate that the EDA@C60 composites demonstrate twice the current density (20 mA cm−2) and a better onset potential (0.2 V vs. SCE) than O–C60 for hydrazine oxidation. The electrocatalytic hydrogen evolution reaction (HER) performance of the O–C60 and EDA@C60 electrocatalysts indicate onset potentials of 0.37 V vs. SCE and 0.20 V vs. SCE, respectively. The experimental and analytical studies found that the nanocomposites with ethylenediamine, i.e., EDA@C60, not only extend the surface area compared to that of O–C60, but also promote the self-decomposition of hydrazine molecules. [ABSTRACT FROM AUTHOR]

For hydrogen generation from catalytic hydrolysis of sodium borohydride (NaBH4), magnetically recyclable Co2P nanosheets as highly efficient catalysts were developed in this work. Briefly, Co(OH)2 nanosheets with an average thickness of 3.8 nm were firstly synthesized by a facile chemical precipitation, followed by controllable phosphidation for the preparation of 2D cobalt phosphides as catalysts. For characterization, a series of advanced analytical techniques were performed, including field-emission scanning electron microscopy, transmission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, N2 adsorption-desorption measurement and magnetism analysis. The effect of the phosphidation temperature on catalyst activity was investigated to determine the optimum conditions. The thin Co2P nanocatalyst prepared at 350 1C presented a maximum hydrogen generation rate of 6.34 L min-1 g-1 using 6 wt% NaBH4-4 wt% NaOH (25 1C), which is much higher than those of similar cobalt-based catalysts and even some noble-metal catalysts reported in the literature. The apparent activation energy of the catalytic hydrolysis was measured to be 47.7 kJ mol-1. The resulting 2D Co2P nanocatalyst with ferromagnetic nature can be magnetically recycled and still retain 70% of the initial activity even after five runs. [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]

Hydrogen generation using a Cu0.33@Co0.22Ni0.45 core–shell nanocatalyst via hydrolysis of ammonia borane (NH3BH3, AB) was performed. The core–shell structure was synthesized with starch as the surfactant. The structure, morphology, and chemical composition of the obtained samples were characterized by X-ray diffraction (XRD), transmission electron microscopy coupled with energy dispersive X-ray spectroscopy (TEM-EDX), inductively coupled plasma emission spectroscopy (ICP), and X-ray photoelectron spectroscopy (XPS). The characterization results showed that the prepared samples possessed a core–shell structure with high catalysis, a high hydrogen release rate (2646 mL min−1 g−1), and low activation energies (37.4 kJ mol−1). In the high cycle performance, 84% of the initial catalytic activity was retained after 5 cycles. The finite element method was used to study the influence of the mechanical properties of the Cu@CoNi core–shell structure on the stability of the catalyst. It was concluded that the Cu@CoNi core–shell possesses excellent structural stability. [ABSTRACT FROM AUTHOR]

Herein we have demonstrated the synthesis of nitrogen vacancy enriched exfoliated B-doped g-C3N4 (e-BCN) through a facile thermal exfoliation method, characterized it using different analytical techniques and compared its photocatalytic activity with that of bulk B-doped g-C3N4 (BCN). The decrease in peak intensity and slight shift of the 2 value in the PXRD patterns confirmed the successful exfoliation of bulk BCN to an e-BCN nanosheet. FESEM and HRTEM images also indicated the formation of a thin layered nanosheet of e-BCN as compared to bulk BCN. The PL and EIS data suggested the reduced recombination rate and superior separation capability of the photo-generated charge carriers of e-BCN. The introduction of nitrogen vacancies on the surface of e-BCN is confirmed by the FTIR and XPS analyses. The increased photocurrent density of 524 μA cm−2 displayed by e-BCN indicated the better availability of photo-generated electrons due to the higher separation of charge carriers than in the bulk BCN. The as-prepared e-BCN nanosheet exhibited enhanced photocatalytic performance 1.2 and 3.7 fold greater than that of bulk BCN towards ciprofloxacin degradation and H2 generation, respectively, under visible light irradiation. The excellent photocatalytic behavior of e-BCN was ascribed to the augmented active sites with reduced recombination efficiency and increased separation ability of the photo-induced e−/h+ pairs of the e-BCN nanosheet. This work suggested the facile fabrication of e-BCN through the thermal exfoliation process and its photocatalytic activity towards pollutant degradation and hydrogen evolution. [ABSTRACT FROM AUTHOR]

The development of organic–inorganic hybrid materials for redox catalysis is key to access new energy conversion schemes and the sustainable production of dihydrogen. Here, bare and P-doped graphene arising from the pyrolysis of biomass (alginate from marine algae) has been used as a support for the growth and stabilization of ultra-small Ru/RuO2 NPs through organometallic synthesis. P-doped graphene allows obtaining smaller and better dispersed NPs in hybrid electrodes of lower roughness and electroactive surface area. Electrochemical activation of the as-synthesised supported nanoparticles by reduction of the passivating RuO2 layer generates excellent HER electrocatalysts under acidic conditions (η10 of 29 mV and 15 mV for the bare and P-doped electrodes, respectively). P doping, identified as surface phosphates by 31P solid state NMR, induces improvement of all HER benchmarking parameters studied, including overpotential and exchange and specific current densities. All studied materials show excellent long-term stability and selectivity for hydrogen generation with no sign of deactivation after 12 h under turnover conditions and almost quantitative faradaic efficiencies. [ABSTRACT FROM AUTHOR]

Transition metal phosphides (TMPs), as an environmentally friendly non-noble metal cocatalyst, play a key role in promoting photocatalytic hydrogen evolution. In this work, three metal phosphating compounds (NiCoP, Ni2P, and Co2P) were synthesized by solvothermal method using red phosphorus as a phosphorus source. The three kinds of co-catalysts were individually loaded onto Zn0.5Cd0.5S by physical agitation method to form binary nanocomposites (ZnCdS/TMPs). The results showed that the three composite photocatalysts all showed excellent HER performance in the Na2S/Na2SO3 sacrifice solution. Among them, the hydrogen production rate of ZnCdS/NiCoP-5% reached 64 μmol at 5 h, which was significantly higher than that of pure Zn0.5Cd0.5S, ZnCdS/Ni2P-5%, and ZnCdS/Co2P-5%. According to the results of various characterization techniques, NiCoP nanoparticles provide more active sites for Zn0.5Cd0.5S and the composite photocatalytic materials exhibit excellent hydrogen evolution performance. Moreover, the Schottky barrier between Zn0.5Cd0.5S and NiCoP nanoparticles effectively enhances the charge separation rate, thus promoting the improvement of photocatalytic hydrogen evolution. Therefore, low-cost transition metal phosphide as a cocatalyst has broad prospects in the field of photocatalysis. [ABSTRACT FROM AUTHOR]

Sustainable hydrogen (H2) production via photocatalytic water splitting is considered the most promising form of energy storage, in which two-dimensional van der Waals heterostructures, composed of two or more 2D monolayer materials, have emerged as excellent H2 storage materials. Here, we have designed two-dimensional vertical ZrS2(HfS2)/BiOCl vdW heterostructures and estimated their electronic and optical properties and the effects of applying strain using hybrid density functional theory calculations. The energetic, dynamic and thermal stabilities were verified via the interface adhesion energy, phonon dispersion curve and molecular dynamics simulations. ZrS2(HfS2) and BiOCl are stacked through weak van der Waals forces, leading to easy growth of the heterostructures. The results show that ZrS2(HfS2)/BiOCl heterostructures possess an intrinsic type-II band alignment that could efficiently reduce the recombination rate of charge carriers. Moreover, the in-plane biaxial strain tunes the bandgap and induces a transition from indirect to direct semiconductor. Additionally, the ZrS2/BiOCl heterostructure band alignment can straddle the water redox potential at pH 0–7. Our theoretical findings are beneficial in revealing the mechanism of enhanced photocatalysis and provide strategies to improve the performance of 2D monolayer materials in solar energy conversion and optoelectronic devices. [ABSTRACT FROM AUTHOR]

Photocatalytic hydrogen production using renewable energy sources is promising as a new method of energy supply. Research on photocatalytic materials has received increasing attention. In this work, efficient photocatalytic hydrogen production was achieved by using ZnIn2S4@CoS2 heterostructures as photocatalysts. The heterostructures were prepared by a simple hydrothermal method using ZIF-67 derived Co3O4 as a precursor. ZIF-67 derived Co3O4 inherits the dodecahedral structure of ZIF-67. ZnIn2S4 nanosheets uniformly grew on the surface of CoS2, which is prepared from Co3O4. The heterostructures achieved a high hydrogen production rate, about 3.2 times higher than that of pristine ZnIn2S4 under simulated sunlight. The enhanced photocatalytic activity can be attributed to the faster electron transfer and more efficient electron–hole pair separation, which are formed in the heterostructure at the interface between CoS2 and ZnIn2S4. This study provides a strategy for noble metal-free photocatalytic hydrogen production using heterostructures. [ABSTRACT FROM AUTHOR]

A heterojunction structure LaVO4/g-C3N4 composite with oxygen defects was successfully prepared. The characterization results show that the recombination of electron–hole pairs could be inhibited by the heterojunction structure. The LaVO4/g-C3N4 composite shows superior photocatalytic water splitting performance for the generation of hydrogen and oxygen under visible light irradiation. Experimental data show that under visible light irradiation, the hydrogen and oxygen evolution rates of the LVOCN1 composite are much higher than those of fresh carbon nitride. Moreover, the photocatalytic activity of LaVO4/g-C3N4 composites could be significantly enhanced by O defects. Mechanism studies display that the possible mechanism of the photocatalytic water splitting reaction is the Z scheme mechanism. [ABSTRACT FROM AUTHOR]

Hydrogen storage in chemicals is regarded as one of the sustainable techniques for tackling the energy-related challenges. However, hydrogen production from ammonia borane (NH3BH3, AB) is restricted by the inherent activity of metallic catalysts, which may be boosted by light irradiation. Herein, Pd-doped Co nanoparticles (NPs) were incorporated into a Zr-MOF composite composed of MXene-derived Ti3C2 nanosheets and UiO-66-NH2 (denoted as TUNS) by a double-solvent approach, obtaining a CoPd@TUNS composite. The optimized Co30Pd@TUNS composite exhibited outstanding catalytic activity for the complete dehydrogenation of AB within 0.6 min under 300 W Xe lamp light, with a high turnover frequency of 130.37 molH2 (molmetal)−1 min−1 at 298 K. The activity of Co30Pd@TUNS increased 10-fold under light irradiation as compared to that in the dark. For photocatalytic dehydrogenation, Co30Pd@TUNS was more active than Co30Pd@UiO-66-NH2 and Co30Pd/Ti3C2. Its excellent performance might be attributed to multiple factors including the photo-harvesting MOF generating electron–hole pairs, Ti3C2 nanosheets promoting the charge separation, and the Schottky effect facilitating electron migration to metal NPs for activating the substrate via an electron-deficient BH3 moiety, along with the attack of photogenerated hydroxyl radicals and water molecules. Moreover, the kinetic study manifested that AB dehydrogenation is a zero-order reaction with regard to the substrate. The great stability and recyclability of Co30Pd@TUNS was also confirmed after 5 runs. This study would widen a pathway for the design of an efficient MOF-based catalyst for hydrogen generation in the energy-related field. [ABSTRACT FROM AUTHOR]

In the present investigation, we report the formation of a metal–metal oxide (Zn/ZnO) nanoscale heterointerfac with concomitant hydrogen generation. The synthesis process is simple and involves the optical illumination of Zn nanoparticles (Zn(NP)) suspended in water. The concomitant hydrogen (H2) evolution during synthesis was found to be linear, and it is dependent on the growth of the Zn/ZnO nano interface. The progressively increasing amount of ZnO relative to Zn(NP) was a limiting factor in H2 evolution. Two different Zn/ZnO nanoscale heterointerfaces were created and samples were extracted at two different stages of the illumination process. The first sample, extracted from the most reactive illumination phase and named Zn(NP)/ZnO-R, had the highest hydrogen evolution reaction (HER) rate. The second sample, extracted from a less reactive illumination phase and named Zn(NP)/ZnO-S, had a lower HER rate. These in situ (solar light-induced) samples were characterized by XRD, HRTEM, and other methods. The optoelectronic features and the photoelectrochemical (PEC) investigations showed the optimal light-harvesting ability of Zn(NP)/ZnO-R and the effective separation of photoexcited charge carriers, leading to remarkable HER performance. During the visible-light-induced (in situ) conversion of Zn(NP) to Zn(NP)/ZnO-R, a concurrent HER rate of 1115 μmol h−1 was observed. Indeed, the photocurrent density value of the Zn(NP)/ZnO-R catalyst is significantly higher than that of Zn(NP)/ZnO-S, pristine Zn(NP), and ZnO. Thus, this study provides new insights into the optimal fabrication of the Zn(NP)/ZnO interface for PEC application with concomitant solar hydrogen generation. [ABSTRACT FROM AUTHOR]

The rational design and facile synthesis of high-efficiency, low-cost, and robust bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are pivotal for hydrogen generation for energy conversion and storage. With this in mind, the synergistic modulation of the architecture, composition, and crystallinity of a non-precious-metal electrocatalyst is considered to be an efficacious strategy to enhance its catalytic activity. Herein, we present a facile route for fabricating a hierarchical Ni-P/NiSex hetero-nanostructured material grown in situ on nickel foam (NF) (denoted as Ni-P/NiSex/NF), which can act as a bifunctional electrocatalyst, via electrodepositing amorphous Ni-P film on the surface of hydrothermally synthesized crystalline NiSex nanorod arrays. The distinctive superhydrophilic 3D structure and useful heterointerface not only afford the greater exposure of active sites, but this material also shows faster charge/mass transport and facilitates the departure of gas bubbles. Meanwhile, benefitting from the regulated electronic structure of NiSex and the synergistic effects of outer amorphous Ni-P and inner crystalline NiSex, the as-fabricated multiphase catalyst exhibits simultaneously excellent electrocatalytic performances during the HER (overpotentials of 98 and 165 mV at 10 and 100 mA cm-2, respectively) and OER (an overpotential of 320 mV at 100 mA cm-2) in 1 M KOH electrolyte. Impressively, a Ni-P/NiSex/NF sample presents robust stability (100 h) during the OER and HER at a large current density. Significantly, an ultralow cell voltage of 1.536 V is required to deliver a current density of 10 mA cm-2 in a two-electrode electrolyzer with Ni-P/NiSex/NF as both the anode and cathode for overall water splitting (OWS), with the demonstration of remarkable durability, and this material far outperforms many recently reported bifunctional electrocatalysts. This work provides a promising strategy for developing efficient bifunctional catalysts for hydrogen production based on the synergistic engineering of the nanostructure design, composition control, and the use of crystalline states. [ABSTRACT FROM AUTHOR]

Lead halide perovskites have exhibited promising achievements in the field of photoelectricity and photocatalysis. However, the toxicity of Pb hampers their practical application. Herein, an environment-friendly and Pb-free double perovskite, NiCoP/Cs2AgBiBr6 (NCP/CABB) composite, was successfully synthesised for the first time via efficient electrostatic coupling. It was applied for H2 generation in an HBr solution. The NCP/CABB composite maintained a steric regular perovskite structure. The optimal 12.5% NCP/CABB composite achieved the highest H2 generation rate (373.16 μmol g-1 h-1), which was approximately 88 times higher than that of pure CABB and was even better than that of CABB/5% Pt. Additionally, the NCP/CABB composite displayed excellent photocatalytic cycling stability in 4 h cycle tests. Due to the loading of NCP nanoparticles with preeminent conductivity, the separation and transfer of photoelectrons were promoted effectively, thereby enhancing photocatalytic performance. This work highlights a feasible strategy with broad prospects for the development of Pb-free perovskite composite catalysts. [ABSTRACT FROM AUTHOR]

The design of economical and efficient electrocatalysts to replace precious platinum-based catalysts for hydrogen evolution reaction (HER) has always been an essential study direction of clean energy technology. In this work, an HER electrocatalyst (Co/WC@NC) was synthesized by pre-self assembly of polyoxometalate (Co4P4W30), cobalt ions and dicyandiamide (DCA) via a one-step calcination process. Co/WC@NC consists of cobalt and tungsten carbide nanoparticles, which are wrapped with nitrogen-doped carbon layers. Co/WC@NC shows good HER capability with relatively low overpotentials of 142 and 158 mV with small Tafel slopes of 93 and 95 mV dec−1, respectively, at a current density of 10 mA cm−2 in acidic and alkaline solutions. Moreover, Co/WC@NC provides satisfactory durability for 24 h in both 0.5 M H2SO4 and 1.0 M KOH. Founded on the above results, good catalytic property of Co/WC@NC can be primarily associated with the synergy between Co and WC nanoparticles, N element doping to make adjustments for the electronic structure of carbon layers, thus speeding up the electron transfer process, as well as graphite-coated carbon layers protecting nanoparticles from oxidation, and improving stability. This study confirms the universal idea to form transition carbides for an efficient electrocatalytic production of hydrogen. [ABSTRACT FROM AUTHOR]

Hydrogen evolution and dye degradation catalyzed by environmentally benign and inexpensive photocatalyst in aqueous solution is regarded as a promising avenue to effectively address the global energy and environmental crisis. It is difficult for traditional photocatalysts to perform efficient light harvesting, with conducive recycling and promoted charge separation and transport, which limit practical applications in photocatalytic conversion. In this study, a facile template-assisted coaxial electrospinning approach was explored to successfully build close contacted heterojunctions within the interface of g-C3N4 nanosheets and hollow porous TiO2 nanofibers, which significantly increased the separation efficiency of photo-induced electron–hole pairs in the visible-light region. A hollow and porous structure with abundant surface-active sites assisted in inducing multiple light reflection for more efficient light harvesting. Moreover, one dimensional TiO2/g-C3N4 composite nanofibers with a large length-to-diameter ratio would be more attractive for recovery. At the optimal g-C3N4 loading, hollow porous TiO2/g-C3N4-50% nanofibers exhibited the highest rate of hydrogen evolution and RhB degradation. The enhanced photocatalytic performance of hollow porous TiO2/g-C3N4 composite photocatalysts was mainly attributed to the synergistic effect of the hollow porous architecture and heterojunction. This work might make a significant contribution to insight into preparing hollow structure heterogenous nanofiber photocatalysts with improved activities in hydrogen generation and pollutant degradation. [ABSTRACT FROM AUTHOR]