Double-shell structured mixed-spinel oxides for highly efficient oxygen evolution

Abstract

Spinel oxides with both spinel and inverse spinel structures are considered highly promising electrocatalysts for the oxygen evolution reaction (OER). However, simultaneously activating two types of spinel-structured composites is essential to unlock their catalytic potential, yet this remains challenging. Herein, we demonstrate a co-doping strategy to introduce both Ni and Fe elements into phosphorus-modified Co₃O₄ microsphere composites to optimize electron distribution and generate abundant oxygen defects. Additionally, the resulting double-shell structure enables rapid mass transfer and enhanced electrolyte enrichment. As a result, the phosphorus-doped ternary Ni-Fe-Co oxide exhibits a low overpotential of 252 mV to achieve a current density of 10 mA cm⁻², outperforming commercial RuO₂. This work provides an effective approach to enhancing the OER activity of spinel oxides by fabricating dual-type spinel complexes.