Constructing oxygen vacancies by doping Mo into spinel Co3O4 to trigger a fast oxide path mechanism for acidic oxygen evolution reaction

Abstract

The development of non-precious metal electrocatalysts for acidic oxygen evolution reaction (OER) that are highly durable, cost-effective, and efficient is crucial to advancing the use of proton exchange membrane water electrolyzers (PEMWEs). Because of its reasonable activity and stability, spinel Co₃O₄ is regarded as a potential candidate for acidic OER. However, it is still far from industrial requirements owing to the sluggish adsorbate evolution mechanism (AEM) for the OER in acids. Herein, we report the enhancement of the activity and stability of acidic OER on Co₃O₄ by doping a small amount of Mo (∼0.5 wt%). The oxygen vacancies are created by doping Mo to activate the lattice oxygen followed by etching away from the lattice, effectively promoting the fast oxide path mechanism (OPM) for the OER. Meanwhile, its stability is boosted by introducing Mo with variable valence states. As a result, as-fabricated Mo-doped oxygen vacancy enriched Co₃O₄ (V_O-Mo_xCo_3−xO₄) exhibits efficient activity with a current density of 100 mA cm⁻² at an overpotential of 490 mV and Tafel slope of 102.5 mV dec⁻¹ towards acidic OER. Meanwhile, V_O-Mo_xCo_3−xO₄ exhibits high stability and can maintain a current density of 10 mA cm⁻² for 30 h.