Quantum-chemical molecular dynamics study of polaron formation in perovskite NaTaO3 as a water-splitting photocatalyst

Abstract

The water splitting reaction mediated by photocatalysts is attracting much interest in the context of solar energy utilization. However, our understanding of the charge carrier dynamics underlying the photocatalytic water splitting reaction is still limited. Here, focusing on the perovskite-type oxide NaTaO₃, which is an archetypical heterogeneous photocatalyst for the water splitting reaction, the charge carrier dynamics were investigated by a computational approach, i.e., molecular dynamics simulations based on quantum chemical calculations. In particular, the present study sheds light on the formation process of polaron, which is a charge carrier dressed by lattice distortion in its surroundings induced to stabilize the charge carrier itself. The results suggested that the charge carriers are weakly localized and maintain the nanoscale spatial distribution of the charge density, and the change in O–Ta bond lengths is the primary factor in the polaron stabilization. In addition, the structural deformation and the resulting polaron stabilization was observed to be stronger in positive (hole) polarons than negative (electron) polarons.