Peroxide Yield of the (001) La0.6Sr0.4MnO3 Surface as a Bifunctional Electrocatalyst for the Oxygen Reduction Reaction and Oxygen Evolution Reaction in Alkaline Media

Active and stable bifunctional electrocatalysts are required for large- scale deployment of rechargeable metal- air and metal- O2 batteries. This is hindered by the large overpotentials of the oxygen evolution reaction ( OER) and oxygen reduction reaction ( ORR) in alkaline media, where peroxide is an undesired side product. We study the suitability of epitaxial ( 001)- oriented La0.6 Sr0.4MnO3 perovskite surfaces as a bifunctional catalyst using a rotating- ring disk electrode ( RRDE) assembly and focus particularly on the selectivity of the ORR. The peroxide yield is above 50% during ORR- only investigations in the scan range of 0.69 to 0.99 V vs. RHE where the CV traces are reproducible. In contrast, the peroxide yield is drastically reduced during OER- ORR cycling where a peroxide yield below 10% is reached during the ORR in the scan range of 0.74 V to 1.74 V vs. RHE. Our study highlights the importance of the electrode history and thus clearly demonstrates that separate studies of the OER and ORR are insufficient to optimize bifunctional electrocatalysts.