First-principles investigations of novel BaSb_2(1−x)Bi_2xO₆ solid solutions applying for water splitting

In the past few years, a lot of efforts have been made to develop earth abundant semiconductor based photocatalysts for overall water splitting. In this work, novel BaSb_2(1-x)Bi_2xO₆ (x = 0, 0.25, 0.50 0.75, 1) solid solutions have been investigated by using hybrid density functional theory for the application of photocatalytic water splitting. The electronic structure calculations indicate that BaSb_2(1-x)Bi_2xO₆ solid solutions possess visible light response at 50 % and 75 % Bi concentration, which can efficiently utilize visible light for the photocatalytic applications. In addition, the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) have been studied on BaSb₂O₆(10 1¯ 0), 50 % Bi doped BaSb₂O₆(10 1¯ 0) and BaBi₂O₆(10 1¯ 0) surfaces. It was observed that the 50 % Bi doped BaSb₂O₆(10 1¯ 0) surface exhibits good photocatalytic activity at applied potential of 1.23 V towards the OER while in case of pure BaSb₂O₆(10 1¯ 0) and BaBi₂O₆(10 1¯ 0), the limiting potential for the OER are 2.06 and 3.57 eV, respectively. The activity on O-sites of BaSb₂O₆(10 1¯ 0), 50 % Bi doped BaSb₂O₆(10 1¯ 0) and BaBi₂O₆(10 1¯ 0) surfaces is too high for hydrogen emission reaction. However, the Gibbs free energy of H* on Bi-site of the 50 % Bi doped BaSb₂O₆(10 1¯ 0) surface is close to zero, signifying the optimal conditions can be achieved.