Engineering hierarchical MCo2O4/NF nanowire networks via cation substitution for high-performance oxygen evolution reaction

Abstract

Spinel Co₃O₄ has emerged as a highly promising electrocatalyst for the oxygen evolution reaction (OER); however, enhancing the intrinsic activity of its octahedral Co³⁺ sites remains challenging. Herein, we strategically tune the polarization degree of the Co³⁺–O bonds in Co₃O₄ octahedra through cation substitution to synthesize MCo₂O₄ (M = Ni, Zn, Mn) nanowire catalysts with a hierarchical three-dimensional architecture on nickel foam (NF). The compositionally optimized MCo₂O₄/NF catalysts synergistically integrate a one-dimensional nanowire morphology with binary compositional modulation, resulting in elevated densities of catalytically active Co³⁺ sites and oxygen vacancies compared to pristine Co₃O₄/NF. Among the series, NiCo₂O₄/NF exhibits superior OER performance with an overpotential of only 277 mV at 10 mA cm⁻² and a Tafel slope of 91 mV dec⁻¹, significantly outperforming Co₃O₄/NF. The catalyst maintains excellent stability and durability over 24 h of continuous operation in an alkaline electrolyte. This work demonstrates the efficacy of combining cationic substitution with nanowire architectural engineering to enhance the catalytic activity of Co₃O₄ and provides insights for designing high-performance cobalt-based spinel oxide electrocatalysts.