Preparation Of ZnIn₂S₄ Oriented Heterojunction Via Oleylamine Modification And Its Photocatalytic Performance For Hydrogen Production

Solar energy is the ideal energy to overcome the crisis of energy shortage and serious environmental problems.Water splitting into hydrogen fuel via semiconductor photocatalyst using solar energy is a green technology.Because of its potential for solving environmental and energy problems,it has received widespread attention.ZnIn₂S₄,as a layered ternary metal sulfide,it is a typical visible-light-driven semiconductor photocatalyst.ZnIn₂S₄ has the advantages of low toxicity,good crystallinity,and considerable chemical stability.Thus,it is a promising semiconductor photocatalyst material for water-splitting into hydrogen.However,its photocatalytic activity in visible light region is insufficient,which limits its practical application.Therefore,it’s the key to research and develop the ZnIn₂S₄-based semiconductor photocatalysts with high activity and good stability.The construction of heterojunctions is an effective method for the modification of semiconductor photocatalysts.In this thesis,ZnIn₂S₄ heterojunction composite photocatalyst was synthesized by ion exchange method with oleylamine（OLAM）modified ZnIn₂S₄,and its visible light photocatalytic hydrogen production performance was studied.This thesis is divided into three parts:（1）The preparation conditions of ZnIn₂S₄@CdIn₂S₄ heterojunction photocatalyst by ion exchange method using oleylamine-modified ZnIn₂S₄ and the post-treatment approach of the photocatalyst were explored.（2）The ZnIn₂S₄@CdIn₂S₄ heterojunction composite photocatalyst was synthesized by two phase ion exchange method using oleylamine-modified ZnIn₂S₄.When Pt was used as cocatalyst,its photocatalytic hydrogen production performance from water under visible light was explored.The experimental results showed that the photocatalytic activity first increased and then decreased with the increase of the amount of oleylamine.When the amount of oleylamine was 1.2 mmol,the prepared ZnIn₂S₄@CdIn₂S₄ heterojunction has the best photocatalytic activity,which may be attributed to the formation of the J-type heterojunction between ZnIn₂S₄ and CdIn₂S₄,which is beneficial to the separation and transport of photogenerated carriers.（3）ZnIn₂S₄@CdIn₂S₄ composite photocatalyst with J type heterojunction was synthesized by ethylenediamine（en）-assisted two phase ion exchange method using oleamine-modified ZnIn₂S₄.The prepared photocatalysts were characterized by various techniques such as X-ray diffraction（XRD）,UV-vis diffuse reflectance spectra（UV-vis DRS）,Inductive coupled plasma emission spectrometer（ICP）,scanning electron microscope（SEM）,transmission electron microscopy（TEM）,Infrared spectrum（IR）,photoluminescence spectroscopy and photo-current test.The characterization results show that the photocatalyst is flower-like microspheres composed of ZnIn₂S₄@CdIn₂S₄heterojunction nanosheets,in which CdIn₂S₄ grows oriented at the rims of the ZnIn₂S₄nanosheets to form ZnIn₂S₄@CdIn₂S₄ J-type heterojunction.The construction of ZnIn₂S₄@CdIn₂S₄ J-type heterostructure promotes the efficient transport and separation of photogenerated carriers and improves the photocatalytic activity.Thus,the ZnIn₂S₄@CdIn₂S₄-J photocatalyst has good photocatalytic activity and stability under visible light irradiation,with hydrogen evolution activity of about 178μmol h^-1,which is 2.74 times of that of pure ZnIn₂S₄,and far greater than that of CdIn₂S₄.