Preparation Of Two-dimensional Transition Metal Sulfides And Their Photocatalytic Hydrogen Production Performanc

In the context of a two-carbon economy,the search for economical,environmentally friendly and clean energy sources has become urgent.Hydrogen energy is considered to be one of the sustainable energy sources for achieving a low-carbon economy due to its high energy density,wide range of sources and ease of transportation.Among the numerous hydrogen generation technologies,photocatalytic hydrogen production,which converts solar energy into clean hydrogen energy,is one of the ideal solutions for obtaining hydrogen energy.However,the low efficiency of photocatalytic hydrogen production is currently a key issue in this research area.Thus,the design and preparation of efficient and stable photocatalytic materials is the focus of research to improve the efficiency of photocatalytic reactions.Transition metal sulphides have attracted much attention for their low cost,simple synthesis method,diverse optical properties and tunable band gap,but their further application in photocatalysis is limited by their disadvantages such as poor structural stability and fast carrier complexation rate.To address the above problems,the following studies have been carried out in this paper:（1）Using an in situ supramolecular self-assembly method,the in situ controlled conversion of melamine into cyanuric acid and the coupling and encapsulation of the two on the VS_2-xsurface under strong hydrogen bonding,and finally the flower-like VS_2-x@C₃N₄composite photocatalyst（VSCN）was produced by high temperature roasting.Under the condition of no co-catalyst and sacrificial agent,VSCN exhibited excellent photocatalytic hydrogen production rate(9628μmol g^-1h^-1)and synergistic wastewater degradation efficiency（58.6%）.The experimental results indicate that the sulphur vacancies facilitate the formation of tight heterojunctions and the reduction of the interfacial work function,which induce the separation of carriers and the enhancement of catalytic activity.In addition,the core-shell structure was constructed to enhance the stability of the catalyst.（2）The flake Zn_mIn₂S_m+3photocatalyst was successfully prepared by a low-temperature hydrothermal method.When used for photocatalytic overall water splitting,Zn₂In₂S₅exhibited excellent photocatalytic overall water splitting performance with a hydrogen production rate of 2470μmol g^-1h^-1and an oxygen production rate of 1208μmol g^-1h^-1.The experimental results showed that by modulating different Zn/In ratios,resulting in the material exposing a different active surface to the atoms.At an atomic ratio of 1.5,Zn_mIn₂S_m+3photocatalysis exhibits an optimal In-S exposure ratio.The highly exposed In-S bond facilitates the separation of photogenerated carriers and exciton dissociation,and also lowers the surface work function and*OOH activation energy barrier,contributing to the enhancement of photocatalytic overall water splitting activity.