Mixed-Phase TiO2 Nanomaterials as Efficient Photocatalysts

Abstract

TiO2, as one of the most promising photocatalysts, exists different phases such as anatase, rutile and brookite. These phases exhibit different properties and consequently different photocatalytic performances. In addition, mixed-phase TiO2 have been demonstrated to have enhanced photocatalytic activity relative to pure-phase TiO2. In the past two decades, many research works have been done on the synthesis of different kinds of mixed-phase TiO2 and their applications to photocatalysis. In this review, we firstly give an introduction of three main types of TiO2 phases as mentioned above, including their structural properties, stability, phase transformation and photocatalytic activity. And then we pay more attention on the synthesis of the mixed-phase TiO2 . Six preparation methods are introduced in details, which are hydrothermal method, solvothermal method, microemulsion-mediated solvothermal method, sol-gel method, solvent mixing and calcination method and high-temperature calcination method. Following this, three kinds of applications of the mixed-phase TiO2 in the photocatalysis field are comprehensively highlighted, including photocatalytic production of hydrogen, reduction of CO2 and degradation of organic pollutants. As the photocatalytic activity of the mixed-phase TiO2 is usually higher than the single phase TiO2, the mechanism for the enhancing effects of the mixed phases are discussed. Finally, the existing problems of mixed-phase TiO2 are summarized and the application prospects of this kind of nanomaterials are outlooked.