Synthesis And Photocatalytic Mechanism Of Bismuth-Based Heterojunction Photocatalyst

With the rapid development of the economy,the crisis of environmental damage and energy shortage is becoming increasingly serious.Semiconductor photocatalysis is a green and environmentally friendly technique,which can directly utilize sunlight to treat contaminants in the environment and rarely produce toxic disinfection by-products.However,many defects such as a limited range of light response and fast recombination of charge-carriers hinder the popularization and application of photocatalysis in environmental remediation.Bismuth-based semiconductor compounds with unique multi-layered morphology,optical and electrical characteristics.Considering the rich domestic bismuth mineral resource,they have great potential to solve the current energy and environmental problems.However,the photocatalytic performances of the conventional bismuth compounds are still unsatisfactory because of their inherent shortcomings.Therefore,it is of great significance to explore how to improve the photocatalytic activity of bismuth compounds and to utilize the high added value of domestic bismuth mineral resource.Based on bismuth-based semiconductor compounds,three kinds of bismuth-based heterojunction photocatalytic materials with tight contact interfaces were constructed by semiconductor coupling strategy.In addition to the microstructure characterization and photocatalytic activity enhancement analysis of the catalyst itself,the mechanism behind the enhanced photocatalytic performance has been deeply explored.The main research work is as follows:first,g-C3N4 nanosheets were synthesized via thermal condensation polymerization and ultrasonic stripping method,and then a 2D/2D Bi4O5Br2/g-C3N4 composite was prepared in situ by adding BiBr3 and adjusting pH values.HRTEM results show that Bi4O5Br2 and g-C3N4 stack with each other to form a 2D/2D structure in tight contact.The adsorption performance and catalytic activity of the composite were evaluated by adsorption and degradation of two typical dyes and antibiotics.Finally,based on the analysis results of a series of material characterization measurements,the mechanism of enhanced adsorption and photocatalytic performance of Bi4O5Br2/g-C3N4 nanosheets is proposed.The Bi4Ti3O12/Ag3PO4 composite was prepared via calcination and precipitation method,and the silver nanoparticles modified Bi4Ti3O12/Ag/Ag3PO4 Z-scheme photocatalyst was obtained by facile light reduction.The photocatalytic performance of the composite catalyst was investigated by removing two refractory pollutants.It has been shown that the localized surface plasmon resonance of silver nanoparticles not only improves the light absorption but also enhances the charge transfer between interfaces and ultimately promotes the photocatalytic activity.The hierarchical Ti3C2 was obtained via an acid etching method,and then the flower-like BiOC1 was in-situ synthesized on its surface by precipitation method,and finally,the Ag/BiOC1/Ti32C2 composite was obtained followed by light reduction.The phenomenon of delayed electron release of Ag/BiOCl/Ti3C2 composite was found by degradation,ESR tests under light/dark conditions,and long/short-term photocurrent response tests.The electrical storage properties of Ti3C2 MXene were found,thus a memory catalytic mechanism was proposed.