Preparation of ZnO with micro/nano hierarchical structure and its photocatalytic performances

Abstract

Two different morphological ZnO materials with hierarchical micro/nano structures were fabricated through solvothermal method and oxalate method, respectively. Their photocatalytic performances were evaluated by using the degradation of methylene blue (MB) solution as model reaction. The results show that the product via solvothermal method exhibits flower-like micro-spherical appearance assembled by many nano-flakes, while its counterpart derived from oxalate strategy shows micro-rod like morphology constructed by many nanoparticles. ZnO fabricated by oxalate method has much better photocatalytic activity towards MB degradation, whose reaction rate constant is 7.65 times as high as that one obtained by solvothermal method. The identification results for active radicals verify that ·OH and ·O2- are both formed in the two samples when they are irradiated under ultraviolet light. However, due to their diverse band structures, there is difference in number of active radicals produced in the reaction system, which can further lead to different photocatalytic efficiency for MB degradation. As for oxalate-derived ZnO, greater number of ·OH and ·O2- can be formed under the irradiation of ultraviolet light. Meanwhile, ·OH with strong oxidation capacity plays a dominant role in the photocatalytic reaction system. As a result, it possesses more excellent property in degradation of MB than that of ZnO originated from solvothermal method.

Keywords

• zno
• solvothermal method
• oxalate method
• photocatalysis
• oxygen vacancy