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sprik3_2015

Activation of the discharge of species adsorbed on oxide surfaces

Oxides are ionic systems capable of stabilizing charged surface species (see also project 1). The discharge of these species by an applied bias potential or photo holes and electrons is activated and is of primary concern for the efficiency of the oxide as an electro or photo catalyst. Of particular relevance is the oxidation of adsorbed water or hydroxide groups. There are strong indications that the vertical ionization levels of these elementary aqueous species are below the valence band maximum of the oxide. These states can therefore be considered as resonant impurity levels in the language of semiconductor physics. The objective of the proposed project is to study these oxide surface states using Density Functional Theory (DFT) and DFT based many body perturbation methods (G0W0). Model systems considered are photo-anodes such as TiO2 and WO3 and their interface with vacuum and aqueous solution. The computational software is again the CP2K package.