Preparation Of Modified WO₃-based Heterojunction Materials And Study On Their Photocatalytic And Photoelectrochemical Properties

Photocatalytic technology and photoelectrochemical technology are both energy-saving and environmentally friendly green technologies,whose basic principle is to convert light energy into chemical energy or electrical energy.WO₃is an excellent semiconductor photocatalyst with a band gap width of 2.6-2.8 e V,good response to visible light,non-toxicity,low cost and easy preparation.However,WO₃also has some disadvantages,such as insufficient negative conduction sites and low efficiency of photogenerated electron hole separation,which greatly limits its application in the fields of photocatalysis and photoelectrochemical cathodic protection.Therefore,it is necessary to modify and design WO₃to improve its performance of photocatalysis and photoelectric conversion.Based on WO₃,the performance of photocatalytic hydrogen production and photocathodic protection was improved by constructing an effective heterogeneous junction system.The specific research content has the following three aspects:（1）WO₃/Cd Zn S direct Z-type heterojunction photocatalyst was prepared by simple hydrothermal method,and its photocatalytic hydrogen production was tested.The results showed that the photocatalytic performance of WO₃/Cd Zn S was better than that of single phase WO₃and Cd Zn S.The compound photocatalyst produced 63.4178 mmol of hydrogen in 4 hours,and it had good photocatalytic stability.The enhanced photocatalytic hydrogen production can be attributed to the direct Z-heterojunction system,which not only effectively separates photogenerated carriers,but also has a strong redox capability.（2）WO₃/Cd_0.97Zn_0.03S composite photocatalyst was designed by solvothermal method(the following Cd_0.97Zn_0.03S is abbreviated as CZS),and then it was compounded with Co S_xnanoplates to obtain WO₃/CZS/Co S_xcomposite photocatalyst for photocatalytic hydrogen production.The physical characterization results show that the WO₃nanorods coated with CZS particles adhere to the Co S_xnanorods and form a heterogeneous structure.The hydrogen evolution rate of the composite photocatalyst was117.48μmol/h,which was higher than that of single-phase WO₃,CZS and double-phase WO₃/CZS.The enhanced photocatalytic hydrogen production was attributed to the formation of double Z-type heterogeneous structure,which promoted the transfer of photogenerated carriers and inhibited the recombination of photogenerated electrons and holes.（3）The WO₃nano-flower electrode was prepared,and then nitrogen-doped carbon quantum dots（NCDs）were deposited on the surface of the WO₃nano-flower electrode,furthermore,Zn In₂S₄with negative conduction potential was further deposited,WO₃/NCDs/Zn In₂S₄multiphase heterojunction photoelectrode was prepared.The photocathodic protection performance of WO₃/NCDs/Zn In₂S₄heterojunction electrode is better than that of WO₃/Zn In₂S₄heterojunction electrode,because the advantage of the heterojunction accelerates the photocarrier separation.The photoelectrochemical properties of WO3/NCDs/Zn In2S4 photoelectrode show that it has the ability of storing electrons and can realize photocathodic protection for a long time.