Selective dissolution of A-site cations of La0.6Sr0.4Co0.8Fe0.2O3 perovskite catalysts to enhance the oxygen evolution reaction

Abstract

Perovskite oxide is a potential alternative to precious metal oxides like IrO2 and RuO2 as electrocatalysts in the oxygen evolution reaction (OER), mostly for its cost-effectiveness and adequate stability. However, the low catalytic activity in the OER limits its practical application. This paper deals with the preparation of perovskite oxides (by the sol-gel method) with enhanced electrocatalytic activity through selective dissolution of A-site cations of La0.6Sr0.4Co0.8Fe0.2O3 (LSCF) in order to tune the A-site cation deficiency. Additionally, a thorough investigation of the catalysts’ OER performance was performed in a 0.1 mol⋅L−1 KOH solution. Based on the results of XRD, SEM, TEM, XPS and ICP-AES, it can be concluded that selective dissolution of Sr cations on A-sites can be achieved using a HNO3 etching remaining the perovskite structure. The OER catalytic activity of LSCF can be effectively promoted after acid etching for 6 h, which can be attributed to the higher surface area (BET result) and ratio of the high oxidative oxygen species (O2−/O−) and surface oxygen species (OH−/O2). Moreover, the LSCF catalysts maintains an appropriate electrochemical stability after acid etching. Our work offers a simple but effective way to modify the perovskite surface so as to boost the OER performance.