Probing lattice oxygen coupling in metal oxides for oxygen evolution reaction catalysis

The oxygen evolution reaction (OER) is the key half-reaction for a range of highly relevant electrocatalytic processes, such as water splitting or CO2 reduction. It was reported, that an alternative OER mechanism could take place in some metal oxides through the direct activation and coupling of lattice oxygen atoms (lattice oxygen-mediated mechanism, LOM), which can offer notably higher reaction rates than the conventional adsorbate evolution mechanism of OER. However, there is a significant lack of understanding on how LOM is activated in metal oxides. In this study, by using atomic pair distribution function analysis (PDF) analysis of total neutron scattering, we plan to probe the local atomic structure of the Co-based perovskite oxides, which have demonstrated one of the highest reported catalytic performances in OER. Precise structural characterization will allow to identify reduced O‒O distances (including the presence of O‒O peroxo-like dimers, trapped molecular O2, etc.) which can be indicative of the LOM OER. The identification of the oxidized oxygen species (e.g., in form of (O2)n‒ dimers (4 > n ≥ 0)) in the oxide lattice would provide the first direct structural evidence for the involvement of oxygen redox in the OER mechanism, constituting a crucial advancement in the area.