Hydrogen Production Performance Research Articles

Experimental investigation of a new photoelectrochemical cell design featuring a unique photocathode configuration for solar hydrogen production

The electrodeposition process and the subsequent assessment of a novel cuprous oxide photocathode are conducted for solar light-based hydrogen production. The mesh dome photocathode helps facilitate the optimal light harvesting, enabling the efficient collection of the maximum accessible light from the solar simulator. This particular design also ensures that light reaches the remote surfaces of the photocathode through penetrating the mesh structure. The electrodeposition method is then employed to coat cuprous oxide onto the stainless-steel electrode. The subsequent examination of this photocathode occurs within an alkaline solution of potassium dioxide to assess its performance in hydrogen production. The study investigates the impact of the new design of the mesh photocathode on hydrogen generation rates, as well as related efficiencies of energy and exergy, under varying light angles during daylight hours. The present experimental findings reveal that the maximum rates of hydrogen production, achieved at a 45° tilt light and 0.25 M KOH, are 15.38 μg/s and it is 15.83 μg/s for vertical light positions. Furthermore, the highest recorded system exergy and energy efficiencies under vertical light conditions are 2.19% and 3.20%, respectively, compared to 2.14% and 3.12% at applying tilted light. The new photocathode design contributes to a notable 80.3% improvement in hydrogen generation rate at tilted light angles in comparison to vertical light conditions.

Construction of 3D MoSx/Zn2In2S5 nanoflower heterojunction for boosted photothermal-assisted photocatalytic hydrogen evolution in biomass solution

Hydrogen production from solar energy conversion method is an attractive strategy to alleviate the energy crisis. The use of non-noble metal cocatalysts instead of noble metal monomers to improve the performance of photocatalytic hydrogen evolution reactions has been pursued by researchers. In this work, we develop a single-photon excited electron transport pathway system for photocatalytic hydrogen production performance studies by coupling 0D MoSx nanodots and 3D Zn2In2S5 nanoflowers. Experimental results combined with DFT calculations show that MoSx not only imparts photothermal properties to the composite material, but also acts as a conduit for electron transport, which can accelerate the rapid separation and transfer of photocatalytic charges. Among them, 3-MoSx/Zn2In2S5 selectively promoted photocatalyzed conversion of benzyl alcohol (BA, 100% conversion) into benzaldehyde (BAD, 96.82% selectivity) by simultaneous co-production of hydrogen (8.74 mmol•g−1•h−1) within 1 h, which is about 7.80 and 2.69 times higher than pure Zn2In2S5, respectively. Further, 3-MoSx/Zn2In2S5 can realize the hydrogen production reaction with glycerol as the substrate with a remarkable effect (up to 5.47 mmol•g−1•h−1). Additionally, 3-MoSx/Zn2In2S5 also showed some hydrogen production performance when other biomasses (glucose, xylose, and cellulose) were used as substrates. This work provides a feasible strategy for the design of photothermal photocatalysts for synergistic hydrogen production from biomass.

(Invited) CdS/Ti-Si-O Composite Photoanode for Photoelectrochemical Hydrogen Generation

Advancements in clean energy drive socio-economic development and foster a sustainable future by restructuring energy systems and promoting low-carbon development. In this paper, we presented a comprehensive investigation on the design and performance characterization of CdS/Ti-Si-O composite photoanodes for photoelectrochemical (PEC) hydrogen generation. Silicon-doped TiO2 nanotube arrays were fabricated through anodization of Ti-5Si alloy, followed by the deposition of CdS using the SILAR (successive ionic layer adsorption and reaction) process, resulting in nanostructured Ti-Si-O photoanodes modified with CdS. The composite photoanodes were characterized in terms of their composition, microstructure, optical properties and photoelectrochemical hydrogen production performance. The composite photoanodes revealed a notable enhancement in PEC hydrogen generation properties with a photocurrent density of 7.86 mA/cm2，which was 19.15 times and 9.59 times to those of the undoped TiO2 photoanode and Ti-Si-O photoanode, respectively. The Si-doping mechanism of the photoanodes was elucidated through Density Functional Theory (DFT) calculations. The synergistic combination of Si-doping and CdS modification represents a novel and promising approach for the design of efficient nanostructured photoanodes.

Nano-Sheets of CsNiVF6 Pyrochlore Electrocatalyst for Enhanced Urea Oxidation and Hydrogen Green Production Reactions

This study presents the successful synthesis of a cesium–nickel–vanadium fluoride (CsNiVF6) pyrochlore nano-sheet catalyst via solid-phase synthesis and its electrochemical performance in green hydrogen production through urea electrolysis in alkaline media. The physicochemical characterizations revealed that the CsNiVF6 exhibits a pyrochlore-type structure consisting of a disordered cubic corner-shared (Ni, V)F6 octahedra structure and nano-sheet morphology with a thickness ranging from 10 to 20 nm. Using the CsNiVF6 catalyst, the electrochemical analysis, conducted through cyclic voltammetry, demonstrates a current mass activity of ~1500 mA mg−1, recorded at 1.8 V vs. RHE, along with low-resistance (3.25 ohm) charge transfer and good long-term stability for 0.33 M urea oxidation in an alkaline solution. Moreover, the volumetric hydrogen production rate at the cathode (bare nickel foam) is increased from 12.25 to 39.15 µmol/min upon the addition of 0.33 M urea to a 1.0 KOH solution and at a bias potential of 2.0 V. The addition of urea to the electrolyte solution enhances hydrogen production at the cathode, especially at lower voltages, surpassing the volumes produced in pure 1.0 M KOH solution. This utilization of a CsNiVF6 pyrochlore nano-sheet catalyst and renewable urea as a feedstock contributes to the development of a green and sustainable hydrogen economy. Overall, this research underscores the potential use of CsNiVF6 as a cost-effective nickel-based pyrochlore electrocatalyst for advancing renewable and sustainable urea electrolysis processes toward green hydrogen production.

Recent Progress of Ion-Modified TiO2 for Enhanced Photocatalytic Hydrogen Production.

Harnessing solar energy to produce hydrogen through semiconductor-mediated photocatalytic water splitting is a promising avenue to address the challenges of energy scarcity and environmental degradation. Ever since Fujishima and Honda's groundbreaking work in photocatalytic water splitting, titanium dioxide (TiO2) has garnered significant interest as a semiconductor photocatalyst, prized for its non-toxicity, affordability, superior photocatalytic activity, and robust chemical stability. Nonetheless, the efficacy of solar energy conversion is hampered by TiO2's wide bandgap and the swift recombination of photogenerated carriers. In pursuit of enhancing TiO2's photocatalytic prowess, a panoply of modification techniques has been explored over recent years. This work provides an extensive review of the strategies employed to augment TiO2's performance in photocatalytic hydrogen production, with a special emphasis on foreign dopant incorporation. Firstly, we delve into metal doping as a key tactic to boost TiO2's capacity for efficient hydrogen generation via water splitting. We elaborate on the premise that metal doping introduces discrete energy states within TiO2's bandgap, thereby elevating its visible light photocatalytic activity. Following that, we evaluate the role of metal nanoparticles in modifying TiO2, hailed as one of the most effective strategies. Metal nanoparticles, serving as both photosensitizers and co-catalysts, display a pronounced affinity for visible light absorption and enhance the segregation and conveyance of photogenerated charge carriers, leading to remarkable photocatalytic outcomes. Furthermore, we consolidate perspectives on the nonmetal doping of TiO2, which tailors the material to harness visible light more efficiently and bolsters the separation and transfer of photogenerated carriers. The incorporation of various anions is summarized for their potential to propel TiO2's photocatalytic capabilities. This review aspires to compile contemporary insights on ion-doped TiO2, propelling the efficacy of photocatalytic hydrogen evolution and anticipating forthcoming advancements. Our work aims to furnish an informative scaffold for crafting advanced TiO2-based photocatalysts tailored for water-splitting applications.

Boosting the Photocatalytic Performance of g-C3N4 through MoS2 Nanotubes with the Cavity Enhancement Effect.

The development of catalysts with high photon utilization efficiency is crucial for enhancing the catalytic performance of photocatalysts. Graphitic carbon nitride (g-C3N4) is a prominent material in the field of photocatalysis. However, it still exhibits drawbacks such as low utilization of visible light and severe recombination of photogenerated carriers. To address these issues, this study employs MoS2 nanotubes (NTs) as cocatalysts and constructs MoS2 NTs/g-C3N4. The MoS2 NTs/g-C3N4 exhibits a significant cavity enhancement effect through multiple light reflections. This results in a broad spectral absorption range and high photon utilization efficiency, while also reducing the recombination of photogenerated carriers. The photocatalyst demonstrates outstanding performance in both photocatalytic hydrogen production and photodegradation of organic pollutants. Specifically, the hydrogen production rate is 1921 μmol·g-1·h-1, which is approximately 2.4 times that of g-C3N4. Furthermore, the photodegradation rate of Rhodamine B reaches 98.6% within 30 min, which is approximately three times higher than that of g-C3N4. Free radical capture experiments confirm that holes (h+) are the primary active species in photodegradation. A plausible photocatalytic mechanism for the catalyst is proposed. This study provides valuable insights into the development of heterojunction photocatalysts with high photon utilization efficiency.

Catalytic performance of modified carbon black on methane decomposition for hydrogen production.

Carbon-based catalysts catalyze methane decomposition to produce hydrogen is a very attractive technical route. Carbon black in carbon-based catalysts has the advantages of high catalytic activity, good stability and better tolerance to toxic impurities such as sulphur in the feedstock, which has become a hot topic of research for many scientists. In this work, the effect of heat treatment on the structural and surface properties of carbon blacks and their catalytic performance in hydrogen production from methane decomposition was investigated. A commercial carbon blacks N110 was selected to heat treatment with nitrogen or carbon dioxide atmosphere at 850 °C, respectively. The Raman spectrums indicated that the graphitization degree of modified carbon under two atmospheres were promoted with the treatment time increasing. BET results revealed that the specific surface area of the carbon black treated under carbon dioxide increased, while the specific surface area was unchanged for that of the carbon black treated under nitrogen. The catalytic test of the two modified carbon blacks for methane decomposition exhibited the almost same activity, which meant that the graphitization degree of carbon black is the key factor for methane decomposition rather than the specific surface area. It was suggested that highly graphitized carbon black could be used as the potential catalysts for hydrogen production from methane decomposition.

Facile Fabrication of SrTiO3/In2O3 on Carbon Fibers via a Self-Assembly Strategy for Enhanced Photocatalytic Hydrogen Production

Photocatalytic water splitting by semiconductors is considered a promising and cost-effective method for achieving sustainable hydrogen production. In this study, a CF/SrTiO3/In2O3 photocatalytic material with a double-layer core–shell structure was developed. The experimental results indicated that the produced CF/SrTiO3/In2O3 composite fiber displayed superior photocatalytic hydrogen production performance, achieving a hydrogen evolution rate of approximately 320.71 μmol/g·h, which is roughly seven times higher than that of the CF/SrTiO3 fiber alone. The enhanced photocatalytic activity of the CF/SrTiO3/In2O3 fiber can be attributed to the heterojunction structure enriched with oxygen vacancies. It was found that these oxygen vacancies created defective states that served as traps for photogenerated electrons, facilitating their migration to the surface defect states and enabling the reduction of H+ in water to produce hydrogen. Furthermore, the synergy between the heterojunction structure and the conductivity of the carbon fiber promoted the generation and migration of photogenerated electrons, reduced the recombination of photogenerated electron–hole pairs, and ultimately improved photocatalytic hydrogen production. This study presents a new approach for designing efficient photocatalysts with surface oxygen vacancies on carbon fibers, providing new insights into the sustainable application of photocatalysts.

Study on the impact of methanol steam reforming reactor channel structure on hydrogen production performance

The design and operation of embedded reactors involve chemical reaction efficiency issues, with the main consideration being heat and mass transfer characteristics. The contact area of the porous catalytic coating with methanol is affected by the reactor structure, to improve the hydrogen yield and reveal the mechanism of the channel structure on the hydrogen production performance, the hydrogen production performance of circle-triangle, circle-square, square-circle, square-square, and triangle-circle channels was investigated. The reasons for the differences in methanol conversion, hydrogen, and carbon monoxide selectivity were analyzed from the perspective of heat and mass transfer using a three-rate reaction mechanism. The results showed that the circle-triangle channel performed outstandingly in the hydrogen production from methanol steam reforming with 98.61 % methanol conversion, 88.74 % hydrogen selectivity, and 29.06 % CO selectivity. The shapes and sizes of the different channel structures affect the fluid flow pattern and velocity distribution, which in turn affect the mass transfer efficiency and lead to differences in hydrogen production performance. The circle-triangle channel exhibits superior heat transfer and material transport performance, which can improve the hydrogen production efficiency of methanol steam reforming and help provide an important reference for the embedded reactor design.

Size engineering of porous CuWO4–CuO heterojunction for enhanced hydrogen evolution in alkaline media

Constructing electrocatalysts with heterogeneous interfaces is of great significance for improving the performance of electrocatalytic hydrogen production. In this work, CuWO4·2H2O–CuO (P-CWOC) was synthesized by hydrothermal method, and spherical porous CuWO4–CuO (CWOC) was obtained through annealing treatment. The size of CuWO4–CuO can be controlled from 72 to 221 nm by regulating the supersaturation of the solution. Among them, CuWO4–CuO with a particle size of 72 nm (CWOC-72) possesses the most oxygen vacancies and the largest specific surface area. The W atom in the heterostructure of CuWO4 and CuO can affect the electronic structure of Cu atoms, and the presence of oxygen vacancies is beneficial for increasing the surface oxygen affinity of the composite material. Benefitting from the largest number of oxygen vacancies and the largest specific surface area, the CWOC-72 own the best catalytic performance compared to the other four catalysts. The overpotential at a current density of 10 mA cm−2 is 121 mV, and the Tafel slope is 70 mV·dec−1. Its excellent stability was confirmed by chronoamperometry, in-situ XRD, and in-situ Raman spectroscopy, and its alkaline HER performance is superior to most CuO-based catalysts.

Encapsulated Dye in Coordination-Assembled Octahedron for Visible-Light-Driven Proton Reduction and Nitroaromatic Hydrogenation.

To mimic the finely tuned natural photosynthetic systems, a large metal-organic octahedron was synthesized by one-pot self-assembly with modified triphenylamine ligands and redox-active cobalt ions. By encapsulating an organic dye, fluorescein (Fl), within the inner cavity of the octahedron, the host-guest supramolecular system was provided for light-driven hydrogen production. The intimate distance between the redox site and the photosensitizer in the supramolecular metal-organic cage allowed the photoinduced electrons to transfer from the excited state Fl* to the redox cobalt center in a pseudo-intramolecular pathway. The supramolecular system showed good performance in light-driven hydrogen production and the reduction of nitroaromatic compounds. Control experiments based on a mononuclear compound resembling a cobalt corner of the octahedron and inhibitor competition provided evidence of enzyme-like catalytic behavior. The supramolecular reaction pathways within confined spaces contribute to the superior activity of the host-guest system.

Structural optimization and electrocatalytic hydrogen production performance of carbon-based composites: A mini-review

The energy demand has increased significantly in recent years and it is urgent to develop a renewable energy system that is highly efficient and non-noble metal-based. Hydrogen energy is an environmentally friendly energy source with abundant resources, which can be used to solve the problem of high energy demand without greenhouse gas emissions. However, the development of catalysts for hydrogen production technology by electrolysis of water is slow, mainly due to the complexity of the electrolysis hydrogen generation process, low hydrogen production efficiency, weak electrode material activity and high cost. Among the non-noble metal-based catalysts, carbon-based materials have high conductivity, tunable chemical bonding, and easily modified morphology, making them beneficial to achieving efficient hydrogen production, though pure carbon composites suffer from few surface-active sites and unmoderated hydrogen bonding energy, which need to be further optimized. The principle of electrocatalytic hydrogen production from the perspectives of reaction thermodynamics and kinetics is analyzed and discussed in this paper. Thermodynamics of electrocatalytic hydrogen production is reflected by the Gibbs free energy of hydrogen adsorption (ΔGH*) and electrode potential (E). Reaction kinetics of the electrocatalytic hydrogen production process are reflected by overpotential, Tafel slope and exchange current density. Structural optimization methods of carbon-based composite materials and hydrogen production performance after structural optimization are also summarized. Structural optimization methods of carbon-based composite materials mainly include introducing active sites, improving conductivity, increasing specific surface area and introducing self-supporting materials. Finally, prospects are proposed for the development direction and existing problems of electrocatalytic hydrogen production performance of carbon-based composites.

A novel additive manufacturing strategy with high hydrogen production for ordered-porous stainless steel catalyst support

This paper proposes to improve hydrogen production performance of ordered-porous stainless steel by increasing its forming structure parameters. Firstly, selective laser melting additive manufacturing of ordered-porous stainless steel is carried out through designed orthogonal experiment table, to obtain its forming structure parameters under different manufacturing process parameters. Then, different forming structure parameters of ordered-porous stainless steel are converted into a comprehensive index by grey relation theory, which is grey relational degree (GRD). When powder thickness, scanning speed, scanning space and laser power are 30 μm, 800 mm/s, 90 μm and 60 W, respectively, the highest GRD of 0.930 is obtained, when those are 40 μm, 1200 mm/s, 70 μm and 60 W, respectively, the lowest GRD of 0.410 is gained. Finally, catalyst bonding strength and hydrogen production performance of the ordered-porous stainless steels with the above GRDs are verified. It is found that the ordered-porous stainless steel with the highest GRD has higher catalyst bonding strength and higher hydrogen production performance. When 12 mL/h injection rate of methanol–water solution and 250 ℃ reaction temperature are used, CH3OH conversion, H2 flowing rate and CO selectivity of the above ordered-porous stainless steel are 64.3%, 0.396 mol/h and 6.75%, respectively.

Promoting charge separation in CuInS2/CeO2 photocatalysts by an S-scheme heterojunction for enhanced photocatalytic H2 production

Low charge separation efficiency significantly hampers the performance of photocatalytic hydrogen production. Constructing heterojunctions emerges as a crucial strategy to enhance photocatalytic activity by improving charge separation. An S-scheme heterojunction not only effectively separates the photogenerated charge in composite photocatalysts but also preserves optimal redox capabilities. This study presents the first report of CuInS2/CeO2 (CIS/CeO2) and demonstrates how charge separation within CIS/CeO2 to enhance photocatalytic hydrogen production through the construction of an S-scheme heterojunction. The UV–visible-driven hydrogen production rate of CIS/CeO2 is 4.6 and 9.4 times higher than that of CIS and CeO2 alone, respectively. The improved photocatalytic performance primarily stems from enhanced charge separation promoted by the S-scheme heterojunction. The charge transfer pathway was confirmed as an S-scheme mechanism through a combination of band structure experiments, density functional theory (DFT) calculations on work function, internal electric field, and charge differential density distribution, alongside electron paramagnetic resonance (EPR) experiments. Multiple perspectives were employed to elucidate the reasons behind facilitating efficient charge separation. This research provides valuable insights for advancing photocatalytic performance.

Enhanced hydrogen production through methane dry reforming: Evaluating the effects of promoter-induced variations in reducibility, basicity, and crystallinity on Ni/ZSM-5 catalyst performance

The pursuit of sustainable hydrogen production through the conversion of methane (CH4) and carbon dioxide (CO2), two prevalent greenhouse gases, is advanced by utilizing cost-effective Ni-supported catalysts within the framework of methane dry reforming. Utilizing crystalline porous zeolite, specifically ZSM-5, enhances the dispersion of nickel (Ni) across the catalyst surface and within its pore channels, hence increasing catalytic efficiency. Herein, we investigate the impact of incorporating various promoters (Ce, Cs, Cu, Fe, Sr) into the 5Ni/ZSM-5 catalyst, systematically examining how these modifications influence the reducibility, basicity, and crystallinity of the catalyst’s active sites, thereby affecting its hydrogen yield potential.Our findings reveal that the inferior activity of Cu-promoted catalysts is due to the depletion of basic sites and larger NiO crystallite size (than rest-promoted catalysts). The introduction of Fe results in a highly dispersed Ni with a stable NiFe phase, but dilution of active sites results in low hydrogen yield. Conversely, Sr promotion enhances the basicity and accessibility of NiO active sites both on the surface and within the pore channels of the zeolite, leading to a notable hydrogen yield of 28 % at 700℃ after 300 min. Furthermore, the addition of 2 wt% ceria significantly optimizes Ni dispersion within the pore channels and surges the maximum population of basic sites (including the presence of very strong basic sites), achieving 35 % hydrogen yield at 700 °C and ∼ 70 % at 800℃. This investigation underscores the critical role of promoter-induced modifications in enhancing catalyst performance for hydrogen production, contributing to the development of more efficient and sustainable energy conversion technologies.

Efficient photocatalytic hydrogen production of Ni-Co layered double hydroxides (Ni-Co LDHs) anchored with reduced graphene oxide (rGO) hybrid composite

Using a suitable co-catalyst to boost photocatalytic H2 evolution from water splitting is crucial. Herein, we designed pristine NiCo-LDH and reduced graphene-oxide supported nickel-cobalt layered double hydroxide nanosheets (NiCo-LDH/rGO) as photocatalyst for the first time to evaluate the hydrogen production performance. Adding graphene has the potential to significantly increase electrical conductivity, and the supported NiCo-LDH has the potential to significantly reduce the likelihood of graphene self-aggregation. The effectiveness of its photocatalytic hydrogen generation was analyzed using a set of characterizations. The H2 evolution rates for pure rGO were 345.2 μmolh-1g-1, whereas those for Ni-Co LDH/rGO were 578.2 μmolh-1g-1. Average hydrogen generation per hour for the Ni-Co LDH/rGO composite material was 2032.1 μmolh-1g-1, which was 5.8 and 3.5 times that of rGO and Ni-Co LDH/rGO, respectively, NiCo-LDH@rGO's synergistic impact on the NiCo-LDH boosts the H2 generation pathway by increasing the catalyst's stability as well as performance by exposing active sites and speeding up electron transport. The produced nanocomposite shows excellent spatial charge separation and quicker electron transport across the conductive network of rGO, as shown by the photocurrent response test and photoluminescence (PL) spectra. The results of this study provide a fresh perspective on the practical use and synthesis of the inexpensive and effective NiCo-LDH/rGO, demonstrating the standard deviation of logical planning and preparation of high-performance photocatalysts.

Robust and efficient hydrogen production performance using nitrogen- and phosphorus-doped microalgal carbon-based metal-free carbon composite

Carbon-based metal-free catalysts are attracting attention in different applications. However, these metal-free carbon materials do not have sufficient active sites, resulting in low catalytic activity. Therefore, modification of metal-free carbon materials with appropriate approaches is important. The simultaneous doping of different electronegative heteroatoms has a positive effect on catalytic performance due to the synergistic effect caused by the electronic interactions between different atoms compared to mono-doping. In this study, Spirulina platensis, a microalgae species that is easy to culture, was used as the carbon source. First, ammonia (NH3) and phosphoric acid (H3PO4) activation were used to modify the surface of activated carbon obtained from Spirulina platensis by KOH activation (SPAC). Thus, the SPAC surface is enriched with N(SPAC-N) and P atoms whose electronegativity is different from carbon. These modified carbon particles (SPAC-N-P) were used as a metal-free catalyst to increase the H2 production rate from NaBH4 methanolysis. XRD, TEM, TG/DTG, FTIR and XPS analyses were used for the characterization of the obtained catalysts. FTIR and XPS analyses showed successful incorporation of N, P and O atoms. HGR values of 5737, 6104 and 13,052 mL min−1gcat−1 by SPAC, SPAC-N and SPAC-N-P catalysts were obtained, respectively. There is a significant increase in the catalytic performance of the catalysts obtained with both NH3 and H3PO4 activations.

Influence of the modification of chlorophyll-rich extracts on the hydrogen evolution reaction of rGO-based electrocatalysts

The great efforts to develop alternative electrocatalysts for efficient hydrogen evolution reaction (HER) applications through environmentally friendly synthesis still need to be completed. We explore a green route using spinach extract to simultaneously reduce and functionalize graphene oxide (GO). A spinach extract, rich in green reducing agents and chlorophyll, was obtained and modified by saponification and demetallation to yield Chln-H2 and further used to reduce and functionalize GO in a one-step procedure. The resulting RGO/Chln-H2 electrocatalyst was evaluated on the HER by Lineal Sweep Voltammetry (LSV), achieving a current density of −34.84 mA/cm2 starting its activation from an onset potential of −0.68 V vs reference hydrogen electrode (RHE). The effect of saponification and demetallation produces a new metal-free alternative catalyst with increased current density seven times, boosting hydrogen production performance.

Synthesis of Co0·52Cu0·48/Cu@S–C arrays for the enhanced performance of hydrazine-assisted hydrogen production

The development of efficient bifunctional catalysts is the key technology to replace oxygen evolution reaction (OER) with hydrazine oxidation reaction (HzOR) with lower theoretical potential to achieve high efficiency and energy-saving hydrogen production. In this work, the Co0·52Cu0·48/Cu@S–C (−1.3 V) composite with flower-like array was prepared by two-step electrodeposition coupled pyrolysis method. The electrochemical measurements showed that the driving voltages of the optimal composite for HzOR and hydrogen evolution reaction (HER) are respectively −118 mV and 47 mV at a current density (j) of 10 mA cm−2. The excellent performance of Co0·52Cu0·48/Cu@S–C (−1.3 V) composite is attributed to the fact that the flower-like structure exposes more active areas and facilitates the diffusion of electrolyte, the strong electron interaction between Co0·52Cu0·48/Cu and S–C substrate, which can be verified by X-ray photoelectron spectroscopy (XPS), enhances the electrical conductivity, the Co0·52Cu0·48/Cu heterogeneous interface reduces the water dissociation barrier and facilitates the dehydrogenation kinetics of N2H4 determined by density functional theory (DFT) calculations. Due to the excellent performance of Co0·52Cu0·48/Cu@S–C (−1.3 V), the overall hydrazine splitting (OHzS) electrolytic cell was constructed with Co0·52Cu0·48/Cu@S–C (−1.3 V) as electrodes. The results showed the voltages required by the cell are 36, 210 and 282 mV at the current density values of 10, 100 and 200 mA cm−2 respectively, showing that Co0·52Cu0·48/Cu@S–C (−1.3 V) can be used for energy-saving hydrogen production by hydrazine assisted water electrolysis.

Elaborate design and construction of direct Z-scheme ZnIn2S4@BiYWO6 heterojunction catalysts for efficient photocatalytic hydrogen production

Photocatalytic Hydrogen production as one of the effective ways to solve the future energy issues has recently become a research hotspot in the field of renewable energy. However, single-component photocatalysts have poor hydrogen production efficiency due to the narrow light-absorption range, susceptibility to photo-corrosion and low catalytic activity. Herein, novel heterojunction photocatalysts of ZnIn2S4@BiYWO6 with different mass ratios were designed and synthesized using a facile two-step hydrothermal method. Experimental results and analyses show that these heterojunction catalysts exhibit extremely excellent photocatalytic performance for hydrogen production. Especially, the hydrogen production rate of 10ZnIn2S4-BiYWO6 is 73 times higher than that of pure ZnIn2S4. Furthermore, enhanced photocatalytic mechanism and carrier transfer pathway in the heterojunction photocatalyst of ZnIn2S4@BiYWO6 were deeply analyzed and explored in the paper, which confirmed that ZnIn2S4@BiYWO6 is a direct Z-scheme heterojunction architecture. Within such a Z-scheme framework, the presence of a built-in electric field at the interface between ZnIn2S4 and BiYWO6 as well as the energy band bending lead to the direct recombination of electrons and holes with low redox capacity, while keeping the electrons and holes with high redox capacity in each component. Consequently, the photocatalytic activity of the Z-scheme heterojunction system has been greatly enhanced. It is believed that the present work provides valuable guidance for the design and construction of novel Z-scheme heterojunction photocatalysts.