Promoted Performance Of CdS For Photocatalytic Hydrogen Production By Ti₃C₂ MXene Cocatalyst

With the rapid development of society and economy,the traditional fossil energy that human beings rely on is gradually exhausted,and the problem of environmental pollution is becoming more and more serious.Semiconductor photocatalytic technology can convert renewable solar energy into clean hydrogen energy,which is expected to alleviate the two major problems of energy shortage and environmental pollution at the same time,and meet the needs of sustainable development of the society in the future.Cadmium sulfide（Cd S）is a typical visible-light-driven photocatalyst for hydrogen production,which has been studied extensively for many years.However,problems such as easy recombination of photoexcited electron-hole pairs and photocorrosion limit the hydrogen production performance and practical application of Cd S.In the recent years,the newly developed two-dimensional Ti₃C₂MXene material has attracted the attention of researchers in the field of photocatalysis due to its excellent electrical conductivity and high work function value.In this paper,based on the previous work,Ti₃C₂ was used as a co-catalyst of Cd S for photocatalytic hydrogen production,and the influence of its morphology,structure,surface properties and other factors on the performance of Cd S was investigated.Specific research contents are as follows:Firstly,multilayer Ti₃C₂ was prepared by wet chemical method,using titanium aluminum carbide（Ti₃AlC₂）as raw material and HF as etching agent,and then multilayer Ti₃C₂-Cd S binary compound was prepared by a solvothermal method.The results show that when the mass fraction of Ti₃C₂ is 1%of Cd S,the photocatalytic hydrogen production rate of the composite reaches 125.2μmol·g^-1·h^-1,which is 1.2 times of that of pure Cd S.This is because the multilayer Ti₃C₂can not only improve the light absorption capacity of Cd S,but also improve the separation efficiency of the photogenerated electrons and holes of Cd S,thus slightly enhancing the photocatalytic hydrogen production activity of Cd S.In order to further enhance the activity,Li F-HCl mixed acid solution was used to etch Ti₃AlC₂ to obtain a monolayer Ti₃C₂,and then a monolayer Ti₃C₂-Cd S binary composite was prepared by solvothermal method.Because monolayer Ti₃C₂ can expose more active sites,the catalytic activity of monolayer Ti₃C₂-Cd S is 1.5 times higher than that of multilayer Ti₃C₂-Cd S under the same conditions,which indicates that monolayer Ti₃C₂ is more suitable as a co-catalyst for hydrogen production of Cd S.Secondly,in the process of preparing monolayer Ti₃C₂ by wet chemical method,some Ti atoms on the surface of the monolayer Ti₃C₂ will also be etched off,forming Ti defects with strong reductive properties.On the basis of the previous work,this work used the Ti defect on the monolayer Ti₃C₂ surface to in situ reduce auric acid to form Au nanoparticles,and then prepared Cd S@Au/Ti₃C₂ ternary complex by solvothermal method.When the mass fraction of Ti₃C₂ and Au was only 1%and 0.05%of Cd S,the hydrogen production rate of ternary catalyst reaches 5915.3μmol·g^-1·h^-1,which was 22.2 times of that of pure Cd S,and significantly higher than that of binary Ti₃C₂-Cd S and Au-Cd S complexes.This is due to the formation of double Schottky junction at the ternary composite interface,which enables more photogenerated electrons to be transferred rapidly and directionally to participate in the hydrogen production reaction.In this work,MXene and a small amount of precious metals were used as the double co-catalysts to effectively improve the visible-light hydrogen production efficiency of Cd S.This study provides experimental basis and theoretical guidance for the development of efficient,cheap and environmental-friendly materials for photocatalytic hydrogen production,which has a certain research significance for promoting the development of green and sustainable solar energy conversion technology.