Rhodium doping augments photocatalytic activity of barium titanate: effect of electronic structure engineering

Environmentally friendly BaTiO₃ is emerging as a potential photocatalyst due to its tunable electronic structure. Although originally believed to be a poor photocatalyst due to its wide band gap, several strategies have been implemented to reduce its band gap. One such approach is doping, but this often leads to the formation of mid gap recombination centers and diminishes the efficiency of the material. In the present work, we study for the first time the effect of site occupancy of Rh on the electronic structure of BaTiO₃. As the theoretical results reveal that if Rh occupies both Ba and Ti sites simultaneously it leads to the formation of mid gap states, an experimental approach is implemented to reduce the band gap of BaTiO₃ while simultaneously avoiding the formation of recombination centers. The facile one pot hydrothermal approach reported here directs the Rh towards Ba sites leading to a decrease in the band gap due to the appearance of donor Rh³⁺ states, suppressing the formation of Rh⁴⁺ states. A promising photocatalytic activity of 96% degradation of methylene blue dye in 120 minutes was observed for the 0.5 Rh sample indicating the high efficiency of the material.