Water-Splitting Activity of La-Doped NaTaO3 Photocatalysts Sensitive to Spatial Distribution of Dopants

Understanding the science behind highly active materials is essential for advancement in the field of photocatalytic water splitting for solar energy harvesting. Sodium tantalate (NaTaO3) doped with La cations is one of the best engineered materials for efficient water splitting to evolve hydrogen. In this study, physical insights into the sensitivity of the water-splitting activity to the spatial La distribution are discussed. The spatial distribution of La cations placed at the Na site was found to dictate the energy gradient of the conduction band bottom (CBB), resulting in a tunable electron population and hence water-splitting activity. A less homogeneous sample with a sufficiently large CBB gradient exhibited higher water-splitting activity. The mechanism of gradient tuning of the CBB through controlling the spatial dopant distribution is expected to be applicable to a broad range of metal oxide perovskites for artificial photosynthesis.