Facile preparation of ZnO/TiO2 nanocomposite photocatalysts and study of their photocatalytic performance

Abstract

Due to its strong photocatalytic activity, chemical stability, resistance to chemical and optical corrosion, and non-toxic qualities, TiO2 has received a lot of attention as a significant semiconductor material. One of the main areas of research in the field of photocatalysis has always been the system made of ZnO, another significant semiconductor, which has stronger physical and chemical characteristics and photocatalytic activity than TiO2 and ZnO alone.The performance of the photocatalysts can be optimized by adjusting the ratio of the components in the complexes. It was found that the catalytic activity of the particulate ZnO nano photocatalysts could be improved by trace TiO2 addition and high TiO2 concentration in the complex, with higher degradation efficiency for methyl orange under simulated solar illumination. The enhanced performance was attributed to the high photogenerated electron-hole separation rate caused by the increased surface oxygen vacancy defects and the enhanced interfacial charge transfer of the pluralistic heterojunction structure. In addition, there is a certain selectivity of ZnO and TiO2 for the photocatalytic degradation of methylene blue and methyl orange, which is related to the charged nature of the catalyst surface and the ionic nature of the pollutant molecules. The inhibitor studies revealed that the degradation reactions of methylene blue and methyl orange involved the active species hydroxyl radicals, superoxide radicals, and photogenerated holes formed on the catalyst surface, with superoxide radicals dominating the methyl orange reaction. The produced photocatalysts' great stability was validated by cycling experiments. Further research on the impact of catalyst dosage and pH of the contaminant solution on the photocatalytic performance of the catalysts revealed that an increase in catalyst dosage resulted in a greater number of active sites for contaminant molecules and incident light, which increased the efficiency of contaminant degradation. In an alkaline environment, the efficiency of the catalyst for photodegradation of pollutants was significantly increased due to the high concentration of strongly oxidizing hydroxyl radicals contained in the alkaline solution.