Preparation Of SrTiO₃-based Composite Photocatalytic Materials And Their Photocatalytic Properties

Strontium titanate（SrTiO₃）,as a typical perovskite compound and semiconductor material,can be used as semiconductor photocatalyst.The material has unique electronic structure,excellent absorption effect in UV region and high photocatalytic activity.However,the high recombination rate of photogenerated electron hole pairs still exists.How to modify SrTiO₃material to improve its photocatalytic performance is the focus of current research.In this study,based on SrTiO₃,a novel photocatalytic composite material was constructed by means of metal doping and semiconductor composite,so as to improve the separation and migration efficiency of photogenerated electron hole pairs and improve its photocatalytic performance.The results obtained are as follows:1)Ternary PVA/SrTiO₃/Ag₂O composites with high photocatalytic performance were prepared by coprecipitation method.The composition,morphology and optical properties of the composite were characterized and analyzed by means of SEM,TEM,XPS,PL and EPR.The composite was a porous three-dimensional network structure,which can improve the separation and migration efficiency of photogenerated electron hole pairs.When the initial methylene blue（MB）concentration was 20 ppm,catalyst dosage was0.15 g·L^-1and initial p H was 7.0,the degradation efficiency of MB reached 88%in 60 min.The photodegradation process was in accordance with apparent first-order kinetics.The degradation rate of MB is above 65%after repeated use for 3 times.2)La-SrTiO₃/Ag/Ag₂O photocatalyst with z-type heterojunction was prepared by sol-gel method.When the initial concentration of MB is 30 ppm,the dosage of catalyst is0.1 g·L^-1and the initial p H of solution is 7.0,the degradation efficiency of MB can reach98%after 90 min reaction.The photodegradation process conforms to the apparent first-order kinetics.Introducing H₂O₂to construct the photocatalytic and Fenton collaborative reaction system can effect improve the efficiency of catalytic degradation of organic pollutants.The reactive oxygen species in the reaction system were mainly hydroxyl radical（·OH）and superoxide ion radical（·O₂^-）.3)The MC/Mn₃O₄/SrTiO₃microspheroidal photocatalyst was prepared by adding microspheroidal activated carbon（MC）and n-type semiconductor Mn₃O₄using the strategy of precursor transformation.The specific surface area of MC/Mn₃O₄/SrTiO₃could reach 606.91 m²/g,and the photoinduced electron-hole pair recombination could be effectively inhibited.The catalyst has high photocatalytic degradation activity.When the initial methylene blue（MB）concentration is 300 ppm,the catalyst dosage is 0.2 g·L^-1and the initial p H of solution is 7.0,the degradation rate of MB can reach 99%in 60 min.The photodegradation process complies with the apparent first-order kinetics.The degradation rate of MB is more than 70%after repeated use for 3 times..