First principles study of the photo-oxidation of water on tungsten trioxide (WO3).

The photo-oxidation of water on the monoclinic P2₁/nWO₃ (200, 020, and 002) surfaces is investigated using density functional theory calculations, employing the PW91-generalized gradient approximation, and the method developed by No\rskov et al. [J. Phys. Chem. B 108, 17886 (2004)] based on the free energy differences between the reaction intermediates. We first relax the bulk material unit cell and then investigate the relative stability of different surface terminations of WO₃ and analyze the overpotential needed for the photoelectrolysis of water. We found that the rate limiting step is the transfer of a proton from the surface adsorbed OH to the electrolyte, and that the computed overpotential for O₂ evolution (1.04 V) is available upon illumination of the surface with visible light. [ABSTRACT FROM AUTHOR]