Electron-Polaron-Enriched Fe-Doped Co₃O₄ Nanoneedle Arrays Enabled by Tip Curvature and Vacancy Engineering for...

The oxygen evolution reaction (OER) is a key process in various renewable energy conversion systems, yet its sluggish kinetics severely limit overall efficiency. Herein, we co-engineer polaron density and localization through morphology-induced field concentration in V_O-Fe-Co₃O₄ nanoneedles. Fe doping increases tip curvature, concentrating fields and charge, while oxygen vacancies donate carriers and promote small-polaron formation. Tip-localized polarons enrich mobile carriers, strengthen electronic coupling, and optimize ^*OH/^*O/^*OOH adsorption, lowering charge-transfer resistance and accelerating proton-coupled electron transfer. Consequently, the V_O-Fe-Co₃O₄ achieves an overpotential of merely 240 mV at 10 mA cm^-2 with an ultra-low Tafel slope of 30.05 mV dec^-1, and >300 h stability at 100 mA cm^-2 in alkaline media. A zinc-air battery based on V_O-Fe-Co₃O₄ exhibits excellent stability for more than 400 cycles at a current density of 10 mA cm^-2. This work identifies directional polaron control as an effective route to high-activity OER electrocatalysts.