Preparation Of ZnCdS Based Photocatalysts And Its Application On Photocatalytic Hydrogen Evolution

With the increase of people's environmental awareness and the intensification of energy consumption,the development of renewable energy has attracted widespread attention.Solar energy is a kind of radiant energy,without any chemical substances,and it is the cleanest and most reliable energy source.Therefore,converting solar energy into a form of energy that is easy to use has become a hot topic in scientific research.Hydrogen energy is considered as a substitute for fossil energy.Among many methods of produce hydrogen,decompose water into hydrogen under illumination is considered to be one of the most promising solar energy utilization methods.In 1972,Fujishima and Honda reported the water decomposition reaction on TiO₂ semiconductors.Since then,there has been an upsurge in photocatalysis at home and abroad.However,TiO₂ has a large band gap and low visible light utilization.Therefore,development semiconductor materials with narrow bandgap and greater response in visible light region is the focus of future photocatalytic work.In the past 50 years of research,a variety of photocatalytic systems for hydrogen production by hydrolysis have been developed.Despite great progress,there are still some issues,such as low quantum efficiency,poor stability,and expensive materials.ZnCdS,as a new type of photocatalyst,is a compound of ZnS and CdS.The combination of ZnS and CdS solves the photo-corrosion problem of CdS.At the same time,the band gap can be adjusted by adjusting the ratio of Zn and Cd,which successfully solves the main problem of ZnS and CdS as photocatalysts.However,the disadvantages of photo-generated electron-hole recombination and low quantum yield limit its application.In this work,taking ZnCdS as the research object,by adding cocatalysts,adjusting morphology,etc,the catalyst's photo-generated charge separation efficiency were improved,and the best experimental methods and conditions were explored to improve the ZnCdS photocatalytic performance.The main research contents are as follows:The first part:spherical SiO₂ was first prepared by the traditional St?ber method,and then EDTA was used as a complexing agent,zinc acetate,cobalt acetate,and thioacetamide as raw materials,and synthetic ZnCdS was wrapped on a silicon ball.Finally,the spheres coated with ZnCdS are treated with APTES to make them positively charged.By using a supramolecular self-assembly method,the negatively-charged Pt colloid and the positively-charged ZnCdS-coated silicon spheres are tightly combined to produce an efficient SiO₂/ZnCdS/Pt photocatalyst.In this process,the negatively charged metal Pt colloid is obtained by reducing chloroplatinic acid with sodium borohydride.Experiments show that,compared with pure ZnCdS,SiO₂/ZnCdS/Pt not only improves the utilization of visible light,but also promotes the separation and transfer of charges,thereby improving its hydrogen production activity under visible light.The second part:using EDTA as a complexing agent to wrap ZnCdS on SiO₂,and then depositing NiS on SiO₂/ZnCdS by photodeposition method,a low cost and high visible light activity SiO₂/ZnCdS/NiS photocatalyst was obtained.Compared with pure ZnCdS,SiO₂/ZnCdS/NiS is more conducive to electron enrichment,inhibits photogenerated electron-hole recombination,and improves photocatalytic efficiency.