Dual-Site Catalysis of Fe-Incorporated Oxychlorides as Oxygen Evolution Electrocatalysts

Electrocatalysts with high activity for the oxygen evolution reaction (OER) play a pivotal role in various electrochemical devices such as water electrolyzers and metal–air batteries. Electronic interactions between these catalysts and chemical reactants control the activity and efficiency and hence need to be optimized, but only the cation components have been of interest. Here, through the optimization of both the cation and anion components, we demonstrate that a Ruddlesden–Popper-type oxychloride Sr2Co0.8Fe0.2O3Cl successfully outperforms Ba0.5Sr0.5Co0.8Fe0.2O3−δ, which is a well-known highly active OER catalyst. Moreover, Sr2Co0.8Fe0.2O3Cl also catalyzes the oxygen reduction reaction (ORR) and minimizes the overpotentials of both the ORR and OER, compared with previously reported conventional perovskite-type catalysts. We discuss possible descriptors of the catalytic activity of Sr2Co1–x Fe x O3Cl to clarify the origin of its activity and highlight a new reaction pathway for OER that involves catalysis by both Co and Fe.