The role of the dopant and structural defects on the water absorption and on the H2 formation in the Al, Co and Cu doped SrTiO3 perovskite steps

Abstract

The investigation of the water interaction/dissociation on perovskite surfaces is of great interest because these processes have different implications on ferroelectric phenomena, water splitting and surface catalysis. In particular, the H2 production has several applications in the photocatalytic environmental cleaning and in the atmospheric chemistry. Some fundamental aspects of the water process are still not well understood; hence the detailed study of more realistic models is essential. We have performed density functional calculations of the water interaction on a stepped SrTiO3 (1 0 0) surface, which contains structural defectivities (edges), oxygen vacancies and metal dopants (Al, Co and Cu). Three different water-surface interaction models can be obtained for both clean and reduced steps: one involving a molecular adsorption and two giving a dissociative process. The presence of both the dopant and the oxygen vacancy drives the stabilization of one specific adsorption type. The H2 formation mechanism is investigated and the crucial role of the dopant on the oxygen vacancy formation emerges. Results demonstrate that the water interaction and/or dissociation on ideal surfaces are not fully transferable on more realistic models, hence this study is relevant to understand the water processes on a model closer to materials exposed to standard experimental conditions.