Influence of oxygen evolution during water oxidation on the surface of perovskite oxide catalysts

Perovskites such as Ba_0.5Sr_0.5Co_0.8Fe _0.2O_3-δ (BSCF82) can be highly active for the oxygen evolution reaction (OER) upon water oxidation in alkaline solution. Here we report that BSCF82 can quickly undergo amorphization of its surface at OER potentials, which is accompanied by reduced surface concentrations of Ba ²⁺ and Sr²⁺ ions as well as increased pseudocapacitive and OER currents. Such quick amorphization during OER was also observed for perovskite catalysts with similar OER activities such as Ba_0.5Sr _0.5Co_0.4Fe_0.6O_3-δ and SrCo_0.8Fe_0.2O_3-δ. In contrast, perovskite oxides with lower OER activities than BSCF82 did not undergo this transformation when subjected to identical electrochemical conditions. These findings demonstrate that the active chemistry and structure of oxide catalysts during OER can significantly differ from those of the as-synthesized material and that understanding how the oxide surface may change and impact the OER activity is critical to the design of highly active and stable OER catalysts.