Study On Photocatalytic Performance Of Modification Of Active Surface On ZnIn₂S₄

The excessive development of fossil fuels such as oil,coal and natural gas and the environmental pollution caused by the products have always been problems that need to be solved urgently in the process of rapid economic development.In order to solve the above problems,the use of visible light photocatalytic decomposition of water to produce hydrogen has aroused widespread research interest.On the one hand,the available natural resources such as sunlight and water are inexhaustible.On the other hand,as an ideal secondary energy source,hydrogen has the advantages of large heating value and non-polluting products,which are widely used in industrial production.However,in the process of using semiconductors as photocatalysts to decompose water to produce hydrogen under visible light,the electron-hole pairs generated by light excitation are severely recombined,and the corresponding photocatalytic performance is low.Therefore,it is urgent to find a convenient and effective strategy to solve the above problems and improve the photocatalytic properties in solar hydrogen evolution.The common ternary sulfide of Zn In₂S₄ is widely used in photocatalysts because of its suitable band gap and high stability.Research has found that this layered compound has anisotropic conductivity due to the composition defect in the lattice structure.It shows that the photogenerated electrons tend to travel along the direction perpendicular to the（001）direction and finally reach a specific active surface to undergo a reduction reaction.The same properties also appear in the Zn_mIn₂S_3+m（m=1-5）series of compounds.With the increase of m,the trend of anisotropic conductivity is gradually obvious.However,due to the small area of the exposed active surface during the crystal formation process,most of the photogenerated electron-hole pairs that reach the active surface recombine,resulting in low photocatalytic water splitting activity for hydrogen production.In order to solve the above problems,a convenient synthesis method was designed to selectively form a heterojunction structure on a specific crystal plane,and effectively improve the activity of photocatalytic water splitting to produce hydrogen.Based on the above research,this paper uses microwave-assisted liquid phase method to synthesize Ag₂S/Zn_mIn₂S_3+m（m=1,5）composite materials with different mass fractions.Combined with the photocatalytic hydrogen production activity,the best Ag₂S composite mass fraction is selected.The study found that 3wt%Ag₂S/Zn_mIn₂S_3+mhas the highest photocatalytic activity for hydrogen production by splitting water,among which 3wt%Ag₂S/Zn₅In₂S₈ photocatalytic hydrogen production activity is particularly prominent,as high as 3188μmol.g^-1.h^-1,and the AQY value at 420nm is 13.76%.The microscopic morphology and structure composition of 3wt%Ag₂S/Zn_mIn₂S_3+m material were analyzed by SEM,TEM,XRD,XPS and other characterization methods,and compared with photoluminescence spectroscopy,ultraviolet-visible diffuse reflection,photocurrent,and EIS photoelectric performance tests.In combination,the mechanism of the improvement of 3wt%Ag₂S/Zn₅In₂S₈ photocatalytic activity was explored.Secondly,this experiment also constructed active sites on the Zn _mIn₂S_3+m inert surface to activate the inert surface through the transition metal Ni²⁺doping and the etching reaction of the S site at room temperature.The final product showed a significant performance improvement.The microscopic morphology and structure composition of 3wt%Ag₂S/Zn_mIn₂S_3+m materials were also analyzed by SEM,TEM,XRD,XPS and other characterization methods,and tested with photoluminescence spectroscopy,ultraviolet-visible diffuse reflection,photocurrent,and EIS.In combination,the mechanism of activating the inert surface of Zn_mIn₂S_3+m for improving its photocatalytic activity was explored.