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

TL;DR

This study demonstrates that oxygen molecules adsorb as activated superoxo species on a clean Sr3Ru2O7(001) surface, with adsorption energies influenced by Ca doping and coverage, revealing insights into oxygen activation on transition metal oxides.

Contribution

It provides the first detailed analysis of superoxo species adsorption on Sr3Ru2O7(001) surfaces, combining DFT and RPA calculations to reveal coverage-dependent behaviors and the effects of Ca doping.

Findings

Oxygen adsorbs as superoxo species on Sr3Ru2O7(001).

Ca doping slightly increases adsorption energy at low coverage.

Adsorption energies range from -0.99 eV to -0.49 eV depending on coverage.

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.