Boosted Oxygen Evolution Reactivity by Igniting Double Exchange Interaction in Spinel Oxides

A double-exchange interaction (DEI) was demonstrated to boost the oxygen evolution reaction (OER) in spinel oxides. DEI was ignited by synergistic actions of constructing nanoheterojunctions and creating oxygen vacancy (V_O) in spinel NiCo₂O₄. DEI between octahedrally coordinated Ni and Co resulted in the generation of superior OER active centers Co^(3-δ)+ and Ni³⁺. The multiple synergistic effects empower the electrocatalyst with exceptional OER activity, with an overpotential of 270 ± 3 mV at 10 mA/cm² and a Tafel slope of 39 mV/dec, both of which are among the best values for NiCo₂O₄-based nanostructures, and even better than those for IrO₂ and RuO₂.