Study On Design And Application Of Photocatalyst Based On ZnO And ZnS

Among the plenty of the photocatalysts,ZnO and ZnS have been widely studied and reported because of their strong redox capacity and structural stability.However,their photocatalytic performance will be affected in a certain extent,due to their high photoelectron-hole recombination rate and narrow absorption range of solar energy.Based on the above issues,this thesis used ZnO and ZnS as the matrix to design and prepare three kinds of photocatalysts,and systematically analyzed the methods to improve the photocatalytic performance of composites.The specific research contents are as follows:?1?Using ordered mesoporous ZnO as matrix,and then the chrysanthemum-like ordered mesoporous CeO₂/ZnO composite was synthesized by hydrothermal method.In the prepared composite,the heterojunctions were formed between ZnO and CeO₂,which induced effective charge separation,and the photocatalytic activity of the composites was enhanced.The photocatalytic organic pollutants degradation concurrent hydrogen production performances were shown in the prepared material.The hydrogen production rate reached to 21.19 mmol/g/h in MB water solution which was about 2.4 time as in Me OH water solution,and the photodegradation efficiency was not reduced.?2?Using metal-organic frameworks ZIF-8 material as a precursor,the CeO₂/ZnS-CuS composite was obtained by insitu sulfurization and cation exchange method in this study.Compared with ZnO,ZnS had a stronger redox capacity,and the co-catalyst CuS could promote the separation of electron-hole.According to the photocatalytic performance of the prepared material,when the CeO₂ content was 10 wt%,the sample exhibited the best photocatalytic activity,whose hydrogen production rate highly reacded to 13.463 mmol/g/h.?3?Using metal-organic frameworks MOF-5 material as a precursor,C was doped into the lattice of zinc oxide material?C-ZnO?by calcining.The copper elemental was deposited on the surface of C-ZnO by light reduction method which showed a plasmon resonance effect as noble metals.The nano-sized C-ZnO could better improve the photocatalytic performance.The valence band position of ZnO could be changed by C dopped,it favored the photoreduction of Cu²⁺ to form Cu on the C-ZnO,the reaction between the H⁺ and photoinduced electron to generate hydrogen on the ZnO conduction band.Another,the doping of C reduced the band gap of zinc oxide,and the photocatalyst showed the much better photocatalytic properties under visible light.The photocatalytic properties were sharply improved by copper modification,when the copper doped content was 5 wt%,its hydrogen production rate highly reached to 5.37 mmol/g/h which was about 6.6 times of C-ZnO material.