Theoretical Insight on Anion Ordering, Strain, and Doping Engineering of the Oxygen Evolution Reaction in BaTaO₂N

Oxynitride perovskites such as BaTaO2N are among the most promising materials to achieve efficient direct solar-to-chemical conversion. Albeit photoelectrochemical water splitting has been demonstrated, the required overpotentials remain prohibitively large compared with the theoretically accessible values, particularly for the oxygen evolution reaction (OER). Here, we apply density functional theory (DFT) calculations to investigate the use of strain and cationic doping with Ca and Sr to optimize the OER theoretical overpotential. For the TaON-terminated BaTaO2N (001) surface, 4% compressive uniaxial strain can lower the theoretical overpotential to η = 0.59 V, under operational conditions. For the most stable TaO2N-(100) termination, 1% tensile uniaxial strain, which is perfectly accessible by experiments, is enough to reduce the theoretical overpotential from η = 0.43 V to η = 0.37 V under (photo)electrochemical conditions. This value is close to the minimum predicted theoretical overpotential and points out how strain engineering could be efficiently used to improve the electrocatalytic reactions.