Water interaction with B-site (B = Al, Zr, Nb, and W) doped SrFeO3−δ-based perovskite surfaces for thermochemical water splitting applications

Abstract

Density functional theory (DFT) calculations were performed to study the interaction of water with the SrO and FeO₂ terminations of the SrFeO_3−δ (001) surface, where the effects of the metal dopants (Al, Zr, Nb, and W), surface oxygen vacancies, and oxygen ion migration were investigated. Our calculations showed that the metal dopants benefited the molecular and dissociative adsorptions of H₂O on both the perfect and oxygen-vacancy-containing surfaces. The surface oxygen vacancies were predicted to promote the dissociative adsorption of H₂O and the formation of H₂. For all structures studied, H₂ release was found to be always an overall endothermic process, except for the W-doped structure which will become exothermic at high temperature. On the oxygen-vacancy-containing surface, H₂ generation was predicted to be easier at the SrO termination than the FeO₂ termination. Furthermore, we also investigated the oxygen ion migration mechanism on all surface structures, predicted the behaviour of oxygen migration and the effect of oxygen vacancy defects. Our results showed that Al doping facilitated not only the formation of surface oxygen vacancies, but also oxygen migration from the surface to the subsurface, in contrast to the Zr, Nb and W-doped structures. This study provided significant insights into the interaction of water with the surfaces of doped SrFeO_3−δ perovskite materials for thermochemical water splitting applications.