Understanding the mechanism of water splitting on (111) and (001) surfaces of CsPbI2Br: time-domain ab initio analysis and DFT study

Abstract

Photochemical splitting of water is a promising source of clean and sustainable energy. Perovskites are increasingly being used as photocatalysts. In this paper, we have presented nonadiabatic quantum dynamics simulations (NAMD) and ab initio simulation studies of photocatalytic splitting of water on the (111) and (001) surfaces of CsPbI₂Br. The simulations not only helped identify the surface on which splitting occurred but also provided atomistic insights into this behavior. We proposed a three-step reaction mechanism, comprising photogeneration of charge carriers, followed by hole transfer from the iodine atom to water and splitting of water at the interface. Subsequent to water splitting, a hydrogen bond was formed between H and I. The splitting occurred due to the shifting of p-orbitals of the oxygen atom in the presence of light. We have computed the charge carrier lifetime on the (111) and (001) surfaces. The overlap integral between the conduction band minima (CBM) and valence band maxima (VBM) was suppressed on the (111) surface compared to that on the (001) surface. As a result, charge carriers remained separated for a longer time on the (111) surface and could participate in the water splitting process.