Study On Preparation And Mechanism Of Z-Scheme Cuprous Oxide-Based Photocatalytic Materials

As a typical p-type semiconductor material,cuprous oxide(Cu2O)has been widely used in the field of photocatalysis due to its visible light response,low toxicity,simple preparation process,and no secondary pollution.However,the photocatalytic performance of Cu2O is seriously affected by the problems of easy recombination of photocarriers and narrow response range of visible spectrum.Traditional cuprous oxide matrix composite photocatalytic materials are usually type-II heterogeneous structures.Because the oxidation and reduction reactions of the heterogeneous structures occur respectively in semiconductors with relatively low valence and conduction band levels,the photocatalytic activity is usually reduced.At present,the construction of Z-scheme heterogeneous structures with high conduction and valence band electrode potentials is considered to be an effective way to improve visible light absorption and the efficiency of photogenerated carrier separation and transport.However,there are few reports on the novel structure and excellent performance of Z-scheme Cu2O matrix composites,and further exploration is needed to investigate the mechanism of microstructure,physical and chemical properties of Cu2O matrix composites and the enhancement of photocatalytic properties.In view of this,this paper is based on the strategies of "Z-scheme mechanism","collaborative adsorptionphotocatalytic effect" and "crystal-amorphous interface effect" respectively to improve the photogenerated carrier separation efficiency and visible light capturing ability of Cu2O.ZnO/Cu2O floral nanostructures and crystalline/amorphous Cu2O/Ti-Fe layer metal hydroxides(LDH)have been prepared successfully.The results show that the two Z-scheme Cu2O based photocatalytic materials can significantly improve the photogenic carrier separation efficiency and visible light absorption capacity of Cu2O,which is conducive to increasing the surface reactive sites,and deeply optimize the photocatalytic activity of Cu2O.The main research results of this paper are as follows:(1)ZnO/Cu2O composite photocatalytic materials have been successfully constructed by hexadecyl trimethyl ammonium bromide(CTAB)assisted liquid phase reduction method.The photodegradation results of tetracycline(TC)under visible light irradiation show that the photocatalytic activity of ZnO/Cu2O heterostructures is obviously better than that of traditional ZnO/Cu2O heterostructures,pure ZnO and pure Cu2O,which is about 2.9 times of ZnO and 2.2 times of Cu2O.This is because the larger surface area of the ZnO/Cu2O heterostructure provides more adsorption capacity and active sites for the reaction.Meanwhile,compared with pure photocatalysis,the degradation efficiency of the "synergistic adsorption-photocatalysis effect" is further improved.In addition,the formation of the "Z-scheme mechanism" enables the photogenerated electrons and holes to remain at a higher potential for reaction,which improves the oxidation and reduction capacity and promotes the photogenerated carrier separation.(2)Cu2O/Ti-Fe LDH composite photocatalytic material was successfully constructed by liquid phase synthesis method sacrificing Cu2O template.The photodegradation results of TC under visible light irradiation show that the photodegradation activity of Cu2O/Ti-Fe LDH is 5.2 times and 2.2 times that of pure Cu2O nanospheres and pure Ti-Fe LDH nanosheets,respectively,and has good cyclic stability.The reason is that the large specific surface area of amorphous TiFe LDH nanosheets provides abundant active sites for the reaction,and effectively promotes the separation of Cu2O surface photogenerated carrier under the "crystal-amorphous interface effect".In addition,the formed Z-scheme heterostructures retain high oxidation and reduction potential,which is more conducive to improving the photocatalytic efficiency...