Synthesis Of Ti₃CN MXene And CdS@Ti₃CN@TiO₂ For Photocatalytic Hydrogen Evolution

As a new two-dimensional material,MXene material has attracted extensive attention of researchers since its appearance,and has great potential in the field of new energy.Among them,the conductivity of Ti₃C₂,which has been studied for the longest time and reported the most,still limits the upper limit of the material.Ti₃CN replaces a C atom in Ti₃C₂with an N atom,resulting in an extra lone pair electron,which greatly improves the electrical conductivity of the material.However,there are few studies on Ti₃CN in all circles.The main reason limiting the study is that Ti₃AlCN will get a lot of mesophase in the synthesis process,which leads to low purity sample and cannot be further stripped to get MXene Ti₃CN.This topic starts from the synthesis of Ti₃AlCN,using Ti,Al N,C,Al powder as raw materials,using plasma discharge sintering（SPS）technology,to explore the best powder ratio,heat preservation time and temperature.It was found that high purity Ti₃AlCN could be obtained when the sintering temperature was 1250℃and the holding time was 30 minutes.Li F+HCl method was used to peel the samples,and Ti₃CN with different morphology could be obtained by changing the peeling time:the unique morphology of nano-flower spheres could be obtained after 18 hours of peeling,and the monolithic MXene Ti₃CN could be obtained after 21 hours of peeling.In order to explore the application of Ti₃CN in photocatalytic decomposition of aquatic hydrogen,a Z-type heterojunction composite sample was constructed using CdS as the composite.CdS nanospheres with a diameter of 30 nm were prepared by hydrothermal synthesis.Ti₃CN with different stripping time was composite with CdS nanospheres with different mass ratios.Then the sample was partially oxidized to obtain CdS@Ti₃CN@TiO₂.The best ratio of photocatalytic hydrogen production was determined by hydrogen production test.A series of characterization methods,such as XRD,SEM,Raman and XPS,were used to provide the migration path of photogenerated carriers and explain the mechanism of photocatalysis.The highest hydrogen production efficiency can be obtained by combining Ti₃CN with 20%CdS with the morphology of 18 h nano-flower spheres.The average hydrogen production efficiency is about three times that of CdS nano-spheres in the absence of precious metal co-catalyst.The preparation of CdS@Ti₃CN@TiO₂is relatively simple and has good stability under light,which has great potential in the field of large-scale photocatalytic evolution.