Tuning the electron affinity of cobalt oxide catalysts for robust acidic oxygen evolution

Abstract

Developing acid-stable, active, and cost-effective oxygen evolution reaction (OER) electrocatalysts is essential for efficient hydrogen production via proton exchange membrane (PEM) water electrolysis. However, balancing activity and stability remains a persistent challenge for Co-based catalysts under acidic OER conditions. Here, we report an oxygen-defective Mo-substituted Co₃O₄ catalyst that delivers both enhanced activity and robust stability. The Mo–Co₃O₄ catalyst achieves a low overpotential of 348 mV at 10 mA cm⁻² and maintains excellent durability for over 300 hours at 50 mA cm⁻² in 0.5 M H₂SO₄. The enhanced performance arises from the incorporation of Mo, whose higher electron affinity promotes *OH adsorption and steers the OER through the adsorbate evolution mechanism pathway while suppressing the lattice oxygen-mediated pathway. Theoretical calculations further reveal that the nonbonding Mo–O state effectively stabilizes isolated hole formation under polarization, thereby favoring cation redox over oxygen loss. This work highlights a strategic approach for regulating catalytic pathways and opens new avenues for designing cost-effective, durable OER electrocatalysts for PEM water electrolysis.