Synergistic Interplay between Fe-based Perovskite Oxides and Co in Electrolyte for Efficient Oxygen Evolution Reaction.

Perovskite oxides have been extensively investigated as active electrocatalysts for the oxygen evolution reaction (OER) in alkaline solution. While the OER activity of some perovskite oxides is positively influenced by Fe ions in the electrolyte, the impact of other transition metal ions in the electrolyte remains unclear. In this study, we compared the influence of Co ions intentionally added to the electrolyte on the OER activities of two Fe-based perovskite oxides (Ba0.5Sr0.5FeO3-δ and LaFeO3). While the OER activity of Ba0.5Sr0.5FeO3-δ is significantly enhanced by adding Co ions to the electrolyte, LaFeO3 showed little difference in the OER behavior between the Co-free and Co-containing electrolytes. In the case of Ba0.5Sr0.5FeO3-δ, an amorphous layer was formed, and the Co ions from the electrolyte were incorporated on the surface as a result of OER cycling. On the other hand, Co ions were also detected on the surface of LaFeO3, but its crystalline structure remains unchanged during the OER. Our study suggests that synergistic interplay between the perovskite oxides undergoing a structural transformation at the surface and transition metal ions in the electrolyte can improve the OER activity.