Adsorption of a superoxo O2- species on the pure and Ca-doped Sr^sub 3^Ru^sub 2^O^sub 7^(001) surface

Only recently, the activation of oxygen molecules on clean defect-free transition metal oxide surfaces has been reported, for example on the CaO-terminated surface of the Ruddelsden-Popper perovskite Ca3Ru2O7(001). In this work we show that oxygen molecules adsorb as an activated superoxo species on a clean SrO-terminated surface of Sr3Ru2O7(001). At all coverages, the electrons activating the molecule originate from the subsurface RuO2 layer. At low coverages, the presence of a Ca dopant in the terminating SrO layer slightly increases the adsorption energy. At high coverage, DFT predicts a flat potential energy surface and a preferred adsorption of the O2- near surface cations. Advanced many-electron calculations (RPA) predict adsorption energies of −0.99 eV and −0.49 eV per O2- molecule for low and high coverages, respectively, and a preference for forming line-like structures in the latter case.