Transformation of Fe-B@Fe into Fe-B@Ni for efficient photocatalytic hydrogen evolution

Co-deposition of Ni-Mo alloy film catalysts for hydrogen evolution from an ethylene glycol system

Owing to the depletion of renewable energy sources, manufacturing stable, efficient and economical non-noble electrode materials for the hydrogen evolution reaction (HER) through electrochemical water splitting is a promising avenue. In this work, Ni-Mo alloy films containing different Mo concentrations were synthesized via potentiostatic technique, and the mechanism of Ni2+ and Mo6+ co-deposition in an ethylene glycol system (EG) was recorded. The co-deposition mechanism of Mo6+ and Ni2+ in the EG shows that the existence of Ni2+ can facilitate the reduction of Mo6+, while Mo6+ can impede the reduction of Ni2+. Furthermore, both functions could be reinforced owing to the improved content of Ni2+ and Mo6+ in the EG system. Ni-Mo alloy films containing different Mo concentrations could be obtained from the EG solution, and their microstructures could be changed by changing the Mo content. Scanning electron microscopy micrographs exhibit that Ni-Mo alloy films with 10.84 wt% Mo show a cauliflower-like pattern. Benefiting from the alloying technique to modify the Ni electronic structure with Mo, coupled with the concurrent presence of an appropriate cauliflower-like structure, Ni-Mo alloy films with 10.84 wt% Mo show remarkable catalytic activity and durability with an HER overpotential of 74 mV (η 10, overpotential was recorded at j = 10 mA cm-2) in 1.0 M KOH solution.

Design of a photocatalyst combining graphdiyne (g-CnH2n-2) nanosheets with a PVP-modified co-metal coordination polymer and its hydrogen-evolution performance

Metal coordination polymers are organometallic frameworks in which a metal and an organic ligand are linked via a dative bond. The material in question exhibits ultra-high porosity, large specific surface area, and abundant active sites, which can be customised in terms of morphology, size, and electronic structure through rational design. Graphdiyne, a novel two-dimensional carbon allotrope, boasts structural stability and enhanced electrical conductivity due to its hybridization of sp2 and sp carbons. A metal-organic framework of Co (MOF-67) was synthesized via hydrothermal synthesis. The introduction of polyvinyl pyrrolidone (PVP) served as a structural regulator and surfactant to obtain a more active metal coordination polymer (Co-MCPS). PVP, in its dual role, significantly amplified the catalytic performance of metal coordinate polymers, as demonstrated in a number of experiments. The incorporation of GDY onto the surfaces of MOF-67 and Co-MCPS induced an electron-rich isolation layer, which could effectively sequester oxidation sites, thereby enhancing the rate of charge carrier separation and hydrogen precipitation evolution efficiency.

Synthesis of oriented J type ZnIn2S4@CdIn2S4 heterojunction by controllable cation exchange for enhancing photocatalytic hydrogen evolution

Construction of semiconductor heterojunctions which promote the separation and transport of photogenerated carriers is an effective strategy for improving photocatalytic reaction efficiency. Based on the anisotropic electrical conductivity of layered ZnIn2S4 (ZIS) photocatalyst, an efficient heterojunction should be constructed along the layer plane of ZIS, that is, a J type heterojunction. However, achieving controllable synthesis of the oriented heterojunction of ZIS faces challenges. Herein, we develop a facile, cost-effective and spatially-selective cation exchange synthesis approach to construct J type ZnIn2S4@CdIn2S4 (J-ZIS@CIS) heterojunction using a flower-like hexagonal ZIS as the parent material. The developed synthesis approach can also control crystal structure of the heterojunction component CIS. This work presents a facile and controllable synthesis strategy to construct oriented anisotropic heterojunctions that are otherwise inaccessible. The as-prepared J-ZIS@CIS heterojunction displays a greatly enhanced photocatalytic hydrogen evolution activity with a rate of 183 μmol h-1, 2.77 times higher than that of pristine ZIS. Furthermore, the possible photocatalytic reaction mechanism is presented for the heterojunction.

Tri-functional aerogel photocatalyst with an S-scheme heterojunction for the efficient removal of dyes and antibiotic and hydrogen generation

A novel three-dimensional (3D) S-scheme S-gC₃N₄/TiO₂/SiO₂/PAN aerogel heterojunction photocatalyst (denoted as S-gTAHP) is rationally devised and manufactured by combining electrospinning, calcination, hydrothermal and freeze-drying techniques. The synthesized S-gC₃N₄ molecule is different from traditional g-C₃N₄, which has a small molecular structure similar to melamine. S-gC₃N₄ is embedded in the interwoven network structure of TiO₂/PAN short fibers, and the catalytic system of the S-scheme heterojunction is formed with SiO₂ as a crosslinking agent. S-gTAHP achieves perfect tri-functional photocatalytic capability, including remarkable hydrogen release capacity (806.7 μmol∙h^-1∙g^-1), efficient removal of three colored dyes with removal efficiencies up to 99.43% (MB, 15 min), 96.13% (RhB, 30 min) and 91.32% (MO, 40 min), and a degradation rate of the colorless antibiotic TCH reaching 84.20% in 40 min driven by simulated sunlight. Meanwhile, the effects of pH values and concentrations of contaminant solutions on the removal rates are explored, and the S-scheme mechanism of S-gTAHP strengthening photocatalytic activity is elucidated. The apparently heightened photocatalytic activities of S-gTAHP can be ascribed to the fact that the 3D hierarchical porous structure of the aerogel endows more active centers and enhanced light-harvesting capacity, and the S-scheme heterojunction supplies effective charge migrating channels, thereby affording the carriers with strong redox capability. Furthermore, S-gTAHP holds prominent reusability and is light weight. Hence, efficient and recyclable 3D aerogel photocatalysts with S-scheme heterojunctions have broad application prospects in practical sewage treatment and energy conversion fields.

Synergistic effect of MoO2/CeO2 S-scheme heterojunction on carbon rods for enhanced photocatalytic hydrogen evolution

The separation efficiency of photogenerated carriers is a key factor affecting photocatalytic hydrogen evolution activity. However, loading precious metals is a cost problem, so this work introduces cheap carbon rods...

CdS Reinforced with CoSX /NiCo-LDH Core-shell Co-catalyst Demonstrate High Photocatalytic Hydrogen Evolution and Durability in Anhydrous Ethanol

At present, inefficient charge separation of single photocatalyst impedes the development of photocatalytic hydrogen evolution. In this work, the CoS_X /NiCo-LDH core-shell co-catalyst was cleverly designed, which exhibit high activity and high stability of hydrogen evolution in anhydrous ethanol system when coupled with CdS. Under visible light (λ≥420 nm) irradiation, the 3 %Co/NiCo/CdS composite photocatalyst exhibits a surprisingly high photocatalytic hydrogen evolution rate of 20.67 mmol g^-1  h^-1 , which is 59 times than that of the original CdS. Continuous light for 20 h still showed good cycle stability. In addition, the 3 %Co/NiCo/CdS composite catalyst also shows good hydrogen evolution performance under the Na₂ S/Na₂ SO₃ and lactic acid system. The fluorescence (PL), ultraviolet-visible diffuse reflectance (UV-vis) and photoelectrochemical tests show that the coupling of CdS and CoS_X /NiCo-LDH not only accelerates the effective transfer of charges, but also greatly increases the absorption range of CdS to visible light. Therefore, the hydrogen evolution activity of the composite photocatalyst has been significantly improved. This work will provide new insights for the construction of new co-catalysts and the development of composite catalysts for hydrogen evolution in multiple systems.

Cd0.8Mn0.2S/MoO3 composites with an S-scheme heterojunction for efficient photocatalytic hydrogen evolution

High-performance and noble metal-free MoO3/Cd0.8Mn0.2S nanocomposites were synthesized via a simple direct physical mixing process. Consequently, from the many characterization methods, the obtained MoO3/Cd0.8Mn0.2S composites exhibited excellent photocatalytic hydrogen production performance and stability. The enhanced photocatalytic activity of the MoO3/Cd0.8Mn0.2S catalyst could be ascribed to the close contact interfaces and well-matched band structure of MoO3 and Mn0.8Cd0.2S, which is beneficial to the transport and separation of photonic excitons. Besides, the hydrogen production performance of the MoO3/Cd0.8Mn0.2S composite catalyst was 1.7 times higher than that of the pure MoO3. Based on the results of time-resolved fluorescence (TRPL) and electrochemical measurements, the possible S-scheme heterojunction mechanism of the photocatalytic hydrogen evolution of MoO3/Cd0.8Mn0.2S was proposed. This work has contributed to the transformation of solar energy into chemical energy.

Ni-MOF-74 derived nickel phosphide and In2O3 form S-scheme heterojunction for efficient hydrogen evolution

The composite structure of Ni2P/In2O3 constructs an S-scheme heterojunction that transfers useless electrons and holes to the composite interface for consumption.The loading of In2O3 further increases the photocatalytic hydrogen production activity.