Adsorption of a superoxo O2- species on the pure an Ca doped Sr3Ru2O7(001) surface

Abstract

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 \crosurf. In this work we show that oxygen molecules adsorb as an activated superoxo species on a clean SrO-terminated surface of \srosurf. At all coverages, the electrons activating the molecule originate from the subsurface RuO${}_2$ 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 \oom\ near surface cations. Advanced many-electron calculations (RPA) predict adsorption energies of $-0.99$\,eV and $-0.49$\,eV per \oom~molecule for low and high coverages, respectively, and a preference for forming line-like structures in the latter case.