Theoretical insight into the electronic, optical and photocatalytic properties of InMO4 (M = V, Nb, Ta) photocatalysts

The electronic and optical properties of InMO4 (M = V, Nb, Ta) photocatalysts are studied using first-principles calculations. For all InMO4, the calculated band gaps are larger than the measured optical gaps, indicating the existence of sub-bandgap transitions. Impurity states and excitons are considered to interpret the characteristic absorption onsets in the measured UV-visible diffuse reflection spectra. The novel visible-light-active water-splitting photocatalytic properties of InMO4 are related to the sub-bandgap transitions. Correlation between the impurity states and the photocatalytic activities is discussed for InMO4 via the conventional mechanism of photocatalytic water-splitting on semiconductors. An excitonic mechanism analogous to Photosystem II in plant photosynthesis is also proposed for the photocatalytic water-splitting process on InMO4.