Recent advances in the development of Co₃O₄-based catalysts for acidic oxygen evolution reaction (OER) are reviewed, highlighting structural, electronic and design strategies to enhance activity and stability for practical proton exchange membrane (PEM) water electrolysis applications. Co₃O₄ is a promising non-precious alternative to noble metals like IrO₂ and RuO₂, but long-term stability remains a challenge. The review emphasises key engineering techniques, such as doping, surface modification and defect engineering, to enhance performance for large-scale PEM application. (Image credit: Huihui Li.)

This article belongs to the collection: 2024–25 RACI and AAS Award papers.