Construction Of Transition Metal Sulfide Photocatalyst And Design Of Photoinduced Carrier Transport Pathway

As a kind of clean energy,hydrogen energy has attracted wide attention due to its abundant reserves and superior calorific value.The technology of photocatalytic water splitting to produce hydrogen demonstrates the possibility of using solar energy to split water to produce hydrogen directly and therefore occupies a research hotspot in the field of energy and environment.The design of an efficient,stable,and readily available photocatalyst has become the core of the research.Limited by factors such as small light absorption range,easy corrosion,and too fast carrier recombination,the activity and stability of single-component photocatalysts are not good.Due to the unique structural interaction and electron transfer behavior between different components,the two-component catalyst exhibits a catalytic activity with more application potential than one component.In this paper,the two-component photocatalyst with better hydrogen evolution activity and better cycle stability is designed through morphology control and the construction of a heterojunction structure,explored and solved the problems of photo-corrosion and low carrier utilization.Combining the characterization results,a possible reaction mechanism is proposed,and the catalyst’s internal electronic transition and transfer mechanism is discussed.It provides new ideas for optimizing the design of new photocatalysts and the performance of hydrogen production.（1）Through a simple one-pot hydrothermal method,the composite of Co₉S₈/Bi₂S₃was successfully synthesized with peanut-like BiVO₄as a precursor.After hydrothermal sulfuration,BiVO₄is transformed into Bi₂S₃while maintaining its original peanut-like structure.Meanwhile,Co₉S₈nanoparticles were successfully coated onto the peanut-shaped surface of Bi₂S₃and formed an S-scheme heterojunction with it according to the in situ hydrothermal methods.The special3-dimensional（3D）structure of Bi₂S₃provides a good growth site for 0-dimensional（0D）Co₉S₈to avoid its aggregation,which helps Co₉S₈expose more reaction area.And,the S-scheme heterojunction preserves more effective redox potential for this system,and the 0D/3D spatial structure creates a more efficient transfer path for photogenerated charges,which greatly promotes the effective separation of charges.This cladding structure between Bi₂S₃and Co₉S₈complements the S-scheme heterojunction,which together promotes the improved hydrogen evolution performance of Co₉S₈/Bi₂S₃.（2）Through the simple physical mixing method,the Mo₁₅S₁₉with three-dimensional curd morphology was successfully attached to the layered Co-based zeolite imidazole framework（ZIF-9）.Thanks to the wrinkled structure formed by the free stacking of layered ZIF-9,the curd-shaped Mo₁₅S₁₉can be more firmly absorbed between the ZIF-9 layers.Beneficial from this unique two-dimensional/three-dimensional space structure,the ZIF-9/Mo₁₅S₁₉composite material has enhanced the adsorption capacity and structure of the eosin dye sensitizer molecule in a hydrogen production system using triethanolamine aqueous solution（10vol%）as sacrificial reagent stability.In addition,the introduction of ZIF-9 as a carrier material exposes more reactive sites to Mo₁₅S₁₉.The reasonable construction of the S-scheme heterojunction between the two retains a more effective redox potential in the system,provides a more convenient transport channel for the transfer of photo-generated charges,and promotes the progress of the hydrogen evolution reaction.（3）Using the Co-based zeolite imidazole framework material ZIF-67 with a dodecahedral structure as the carrier material,ZIF-67 was reshaped into cobalt sulfide with a hollow structure through one-step hydrothermal vulcanization.In the hydrothermal process,Mo₂S₃was grown in situ on the surface of Co₃S₄to synthesize a Co₃S₄@Mo₂S₃composite material with a layered core-shell structure S-scheme surface heterojunction was developed.The crisscrossed Mo₂S₃nanosheets that grow on the surface of the hollow Co₃S₄dodecahedron-like thorns can further block the desorption behavior of EY molecules so that the composite exhibits significantly superior cycle stability.Using ZIF-67 with superior specific surface area as the carrier material can also provide more abundant active sites for the system.The unique core-shell structure of Co₃S₄@Mo₂S₃and the S-scheme heterojunction structure formed between the two further synergistically promote the separation of photogenerated carriers and significantly inhibit the recombination electron-hole pairs.By adjusting the amount of Mo element and S element introduced,the maximum hydrogen production efficiency of the composite can reach 7508.0μmol g^-1h^-1.By further optimizing and adjusting the hydrogen production environment,the hydrogen production efficiency of the composite can be further increased to 8820.0μmol g^-1h^-1.The proposal of this strategy provides a new reference idea for the preparation of new two-component photocatalysts based on MOFs.（4）In this case,the Mo₂S₃/Bi₂O₂CO₃composite with a unique n-n heterojunction and two-dimensional（2D）spatial structure was successfully prepared for the first time using the physical mixture method.The percentage of Bi₂O₂CO₃in the composite can be easily adjusted by changing the amount of Bi₂O₂CO₃introduced into the physical mixing process.With a mass percentage of Bi₂O₂CO₃attained 3%to Mo₂S₃,the composite Mo₂S₃/Bi₂O₂CO₃with n-n heterojunction exhibited the highest photocatalytic effect among all as-prepared samples,with a photocatalytic effect 5times higher than pure Mo₂S₃.The presence of Bi₂O₂CO₃and the synergistic interactions of n-n heterojunction significantly reduced the dispersity of short-rod shaped Mo₂S₃and the recombination of photogenerated charge carriers,which effectively promotes the improvement of the hydrogen production performance of Mo₂S₃/Bi₂O₂CO₃.