Hierarchical nano/micro/macro-assembled integrated electrode with high-performance water electro-oxidation

Development of robust and high-performance oxygen evolution reaction (OER) electrocatalysts at high current densities is pivotal for cost-effective clean hydrogen production on a large scale. Herein, the hierarchical Co₃O₄/CoO nanowires@Cu micro-pillars with abundant oxygen vacancies (V_Os) were designed and directly grown on nickel foam, combining robust integrated electrode. This electrode shows a superb OER performance with an overpotential of 304 mV at 100 mA cm⁻². Particularly, it could achieve the industrially required 1000 mA cm⁻² at an overpotential of 391 mV, superior to most reported electrodes. The hierarchical structure of electrode, high conductivity of introduced Cu micro-pillars, and porous structure of Ni foam provide large specific surface areas and open channels for fast mass and electron transfers. DFT calculation reveals the H₂O molecules and the intermediate of OH* are preferably adsorbed on Co(III) site near V_Os due to increased oxygen vacancies, which promotes electrocatalytic performance. This work provides a feasible route to design integrated electrode with excellent OER performance at high current density, which might have a promising future in the application of renewable energy.