ABSTRACT
Up to now, many kinds of semiconductor metal oxides have been widely studied. Among them, TiO2 has been considered as a promising approach to solving environmental and energy problems (Davis and Green, 1999; Du et al., 2011; Fujishima and Honda, 1972; Fox and Dulay, 1993; Fujishima et al., 1994; Hurum et al., 2005; O’Regan and Grätzel, 1991; Tang et al., 2004; Wang et al., 2012), owing to its ability to split water under ultraviolet (UV) light, and its potential in other photoelectron-chemical solar-energy conversion with photochemical stability, non-toxic nature and low cost (O’Regan and Graetzel, 1991). However, the overall efficiency is largely inhibited under sunlight which consists of 43% visible and only 5% UV fraction, due to its wide band gap (3.2 eV for anatase and 3.0 eV for rutile), which nonetheless permits only UV light to be used (Hoffmann et al., 1995; O’Regan and Graetzel, 1991). Thus, it is of significance to develop a photocatalyst that can harness visible light with high efficiency under normal sunlight conditions.
