Controllable Preparation Of Zn-In-S Based Photocatalytic Materials For Hydrogen Production Coupled With Aromatic Alcohols Oxidation

The consumption of traditional primary fossil energy has brought a serious energy and environmental crisis,finding a sustainable energy consumption model has become the most challenging problem in the world.Hydrogen energy is a green and clean renewable energy carrier,and its production technology has received much attention.Photocatalytic hydrogen production coupled with aromatic alcohols is a new,clean,efficient and atom-economical strategy of artificial photosynthesis.This process can not only reduce protons to produce hydrogen,but also generate high value-added fine chemicals.As a key condition for the realization of photocatalytic reactions,catalysts need to have excellent catalytic performance and structural stability.As a new type of bimetallic sulfide photocatalyst,zinc indium sulfur(Zn_xIn₂S_x+3)has a controllable energy band structure and unique physical and chemical properties,which has attracted extensive research interests in the fields of energy and environment.However,the disadvantages of monomeric Zn_xIn₂S_x+3 photocatalysts,such as poor visible light respons and low carrier separation efficiency,limit their photocatalytic activity.Therefore,it has become a research hotspot to explore suitable modification methods to improve the catalytic performance of Zn_xIn₂S_x+3 based photocatalysts for hydrogen production coupled with aromatic alcohols oxidation.In this paper,Zn_xIn₂S_x+3 based photocatalytic materials are taken as the main research object.The synergistic enhancement mechanism for the light response,charge carrier separation and migration,as well as the surface chemical reaction by various modification methods such as defect engineering,energy band modulation of heterojunction,and construction of strong polarized electric field was explored.At the same time,the prepared catalysts were used for hydrogen production coupled with benzyl alcohol oxidation reaction.The specific research contents are as follows:1.Oxygen-doped ZnIn₂S₄（O-ZIS）ultrathin nanosheet and oxygen-deficient TiO_2-x nanocage were prepared by hydrothermal method and high-temperature chemical reduction method,respectively.Then the obtained O-ZIS and TiO_2-x are combined together via electrostatic self-assembly strategy to construct the O-ZIS/TiO_2-xheterojunction.Using DFT theoretical calculations and experimental characterizations,it was found that,benefit by the synergistic effect of defect and doping engineering,O-ZIS/TiO_2-x heterojunction catalysts achieve energy bands with higher redox potential and larger Fermi level difference structural design,which endows it with excellent photocatalytic performance.The photocatalytic hydrogen production coupled with benzyl alcohol oxidation experiments were carried out under visible light,and the optimal O-ZIS/TiO_2-x heterojunction catalyst achieved H₂ and benzaldehyde yields of2584.9μmol g^-1 h^-1 and 2880.5μmol g^-1 h^-1,which are 4.3 times and 4.4 times that of pristine ZIS,even 52.5 times and 66.4 times that of pristine TiO₂,respectively.Besides the hydrogen production activity of the coupling reaction is much higher than that of using sacrificial agents（Na₂S/Na₂SO₃ and triethanolamine）.Mechanism studies such as surface photovoltage（SPV）,in-situ photoelectron spectroscopy（in-situ XPS）and differential charge density calculations found that the O-ZIS/TiO_2-x heterojunction exhibits an efficient S-scheme interface charge transfer mechanism;photoelectrochemical characterization and radical trapping experiments also demonstrated that the heterojunction design can effectively improve the separation and utilization efficiency of photogenerated charge carriers,thereby achieving a substantial increade catalytic activity.This work provides a new and effective strategy for improving photocatalytic hydrogen production performance through reaction path optimization and rational design of photocatalysts.2.Based on the research on O-ZIS/TiO_2-x photocatalysts,ZnIn₂S₄,Zn₂In₂S₅ and Mo-Zn₂In₂S₅ polarized photocatalysts with ultrathin nanosheet structures were synthesized through stoichiometric control and surface metal cluster modification.The polarization electric field effect within the crystal structure of the Zn_xIn₂S_x+3 catalyst is revealed.Theoretical calculations and Kelvin atomic force microscopy（KPFM）tests showed that the polarization modification can greatly increase the polarization electric field strength of Zn_xIn₂S_x+3 along the（001）direction.The polarization field strengths of Mo_1.5-Zn₂In₂S₅ are respectively 9.1 and 3.2 times that of ZnIn₂S₄ and Zn₂In₂S₅,thus effectively promoting the photogenerated charge separation efficiency of the catalyst.In addition,Mo clusters can also be used as active sites for the reaction,which show higher photocatalytic activity for the oxidation of aromatic alcohols coupled with hydrogen production compared with other metals.Among them,the hydrogen and benzaldehyde yields of Mo_1.5-Zn₂In₂S₅ are as high as 41.98 mmol g^-1 h^-1 and 61.86mmol g^-1 h^-1,which are 5.13 times and 5.66 times higher than those of ZnIn₂S₄,3.68and 3.83 times that of Zn₂In₂S₅.This work realized the photocatalytic enhancement of Zn_xIn₂S_x+3 based photocatalysts from the perspective of polarized electric field,which provides an excellent reference for the development of efficient polarized catalysts for artificial photosynthesis.