Water adsorption on ferroelectric PbTiO (0 0 1) surface: A density functional theory study.

In this work, combining the density functional theory (DFT) calculations and the ab initio molecular dynamics (AIMD) simulations, the water adsorption behavior, including the molecular and the dissociative adsorption on the negatively polarized (0 0 1) surface of ferroelectric PbTiO was comprehensively studied. Our theoretical results show that the dissociative adsorption of water is more energetically favorable than the molecular adsorption on the pristine PbTiO (0 0 1) surface. It has been also found that introducing surface oxygen vacancies (O) can enhance the thermodynamic stability of dissociative adsorption of water molecule. The AIMD simulations demonstrate that water molecule can spontaneously dissociate into hydrogen atoms (H) and hydroxyl groups (OH) on the pristine PbTiO (0 0 1) surface at room temperature. Moreover, the surface O can effectively facilitate the dissociative adsorption of water molecules, leading to a high surface coverage of OH group, thus giving rise to a high reactivity for water splitting on defective PbTiO (0 0 1) surface with O. Our results not only comprehensively understand the reason for the photocatalytic water oxidation activity of single domain PbTiO, but also shed light on the development of high performance ferroelectric photocatalysts for water splitting.