Fabio Negreiros Ribeiro
University of ABC, Brazil
Title: Water interaction and dissociation on the (0001) hematite surface: a DFT+U approach
Biography
Biography: Fabio Negreiros Ribeiro
Abstract
Statement of the Problem: A great deal of attention has been devoted to the study of photocatalytic effects on the interface between insulating oxide materials and water. It has been widely demonstrated, for a variety of materials, that water splitting can occur at these surfaces under certain specific conditions. The choice of the best material includes a balance between cost and performance. Among the desired properties, we need a specific band gap and band offset in order for the oxidation and reduction energies of water to be placed inside the band gap. There has been considerable interest in hematite, owing to its low cost and good photocatalytic activity. A considerable amount of theoretical and experimental works characterizing this structure can be found in the literature. The interaction of hematite with water is, therefore, of great interest for both academic and industrial purposes. Methodology & Theoretical Orientation: We performed DFT+U calculations to study the interaction of water with the Fe2O3(0001) surface. Using the CP2K and QE open source softwares, we determined the most stable configurations of a single water molecule adsorbed on the pristine oxygen-terminated surface, and how adding more water changes this interaction. Surface oxygen and iron vacancies were also considered at different charge states. Findings: Ab-initio molecular dynamics simulations at room temperature reveal that water spontaneously dissociates (H2O→H+OH-) at the interface, covering more than 50% of the surface with hydroxyls. Furthermore, in oxygen rich conditions, surface iron vacancies are found to be more stable than the pristine surface as long as the electronic chemical potential is 1eV higher than the Fermi energy. Iron vacancies also increase the water dissociation rate at the interface.