Alternative Materials to TiO2

Abstract

One of the most significant investigations on heterogeneous photocatalytic process can be dated back to the 1970s, when Fujishima and Honda showed that the TiO2 electrode is capable of water splitting under suitable electromagnetic irradiation. Since then, TiO2-based materials have become the dominant photocatalyst and have been investigated for decades due to their abundance, non-toxicity, and relatively high reactivity. However, the bandgap of pristine TiO2 is larger than 3 eV, which can only absorb light that has a wavelength of less than 400 nm. Unfortunately, this portion of photons only corresponds to 4–5 % of the solar spectrum, which has limited the application of photocatalysis at an industrial scale. Moreover, the conduction band position of TiO2 is only slightly negative relative to that of the proton reduction potential, resulting in a relatively poor reduction power for solar-to-fuel conversion. Therefore, the development of alternative photocatalysts with visible light absorption and tunable properties is essential in the application of photocatalysis techniques.