Enhancement of Oxygen Evolution Activity of Ruddlesden-Popper-Type Strontium Ferrite by Stabilizing Fe4 +

Abstract

Development of active iron based water oxidation for designing an ideal artificial photosynthesis devices operating under benign neutral pH is highly demanded. We investigated the electrocatalytic activity of Ruddlesden-Pop-per-type strontium ferrite (Sr 3 Fe 2 O 7) toward the oxygen evolution reaction (OER). Owing to the temperature-dependent efficiency of the charge dispro-portionation of Fe 4+ , the OER activity of Sr 3 Fe 2 O 7 varied with the temperature, and the onset potential for the OER at a neutral pH underwent a negative shift of approximately 200 mV by increasing the temperature for the stabilization of Fe 4+ . When metal substitution was made to Sr 3 Fe 2 O 7 for stabilizing Fe 4+ at room temperature, the temperature dependence of the OER activity disap-peared and the OER was driven at a small overpotential without increasing the temperature, indicating that the stabilization of Fe 4+ is substantially im-portant for achieving high OER activity.