Sustainable oxygen evolution electrocatalysis in aqueous 1 M H 2 SO 4 with earth abundant nanostructured Co 3 O 4 .

Earth-abundant electrocatalysts for the oxygen evolution reaction (OER) able to work in acidic working conditions are elusive. While many first-row transition metal oxides are competitive in alkaline media, most of them just dissolve or become inactive at high proton concentrations where hydrogen evolution is preferred. Only noble-metal catalysts, such as IrO 2 , are fast and stable enough in acidic media. Herein, we report the excellent activity and long-term stability of Co 3 O 4 -based anodes in 1 M H 2 SO 4 (pH 0.1) when processed in a partially hydrophobic carbon-based protecting matrix. These Co 3 O 4 @C composites reliably drive O 2 evolution a 10 mA cm -2 current density for >40 h without appearance of performance fatigue, successfully passing benchmarking protocols without incorporating noble metals. Our strategy opens an alternative venue towards fast, energy efficient acid-media water oxidation electrodes.