Cobalt-based oxygen evolution catalyst as active and stable as iridium in acidic media

Abstract Transition metal oxides have attracted attention as the most promising alternatives to expensive Ir-based electrocatalysts for oxygen evolution reaction in alkaline media. However, transition metal oxides are generally unstable and dissolve in acidic electrolytes and at high anodic potentials. In this study, various bimetallic RuCo oxide catalysts were prepared with low noble metal content, by aerosol pyrolysis followed by heat treatment, for developing highly active and stable electrocatalysts in acidic media. During pyrolysis, Ru atoms were incorporated into the Co oxide lattice to form mixed metal oxide, and the RuCo oxide with 16 wt% Ru and additional thermal treatment in air at 300 °C, showed higher oxygen evolution reaction performance. The results indicated that the enhanced bonding between Ru and Co atoms, higher Co3+ ions, and improved surface hydrophilicity and micropore volume owing to the post-heat-treatment, affords higher OER performance comparable to commercial Ir black, and displays superior stability during the accelerated stress test between 1.3 and 1.65 V (vs. reversible hydrogen electrode).