Activating ORR and OER in Ruddlesden-Popper based catalysts by enhancing interstitial oxygen and lattice oxygen redox reactions

Numerous theoretical and experimental works about Ruddlesden-Popper (RP) based oxygen catalysts were based on the critical assumption: oxygen vacancies do exist in the perovskite-like layer, and which with the interstitial O²⁻ (in rock-salt (AO) layers) were the two key influencing factors to determine RP’ oxygen exchange rate and oxygen catalytic ability. But overall, the presence or absence of critical oxygen vacancies in the perovskite-like layer of RP oxides is still unclear. Here, from our experimental results, no oxygen vacancy was detected in the perovskite-like layer of RP series materials. Herein, for the Ruddlesden-Popper based oxygen catalysts, we proposed that more interstitial O²⁻ in the AO layers and high-active lattice oxygen ions in the perovskite-like layers are the determinant factors to activate the ORR and OER. Accordingly, we reveal that the high-valence ion doping strategy for RP electrode can enhances the redox reactions while improving the lattice-oxygen activity and interstitial O²⁻ concentration, and then benefiting the ORR and OER activity.