Two-dimensional bimetallic CoFe selenite via metal-ion assisted self-assembly for enhanced oxygen evolution reaction

Abstract

It remains a great challenge to develop high performance and cost-efficient electrocatalysts to be applied in the oxygen evolution reaction (OER) in view of its sluggish kinetics. Herein, a 2D CoFe selenite is prepared as a promising OER catalyst in high yield via a simple metal-ion self-assembly strategy under hydrothermal conditions. The obtained CoFe selenite exhibits superior OER electrocatalytic activity with a relatively low overpotential of 257 mV at a current density of 10 mA cm⁻², a small Tafel slope of 45.6 mV dec⁻¹ in 1.0 M KOH electrolyte; particularly, it has excellent intrinsic activity with a high mass activity of 730.9 A g⁻¹ at an overpotential of 0.49 V. Besides, it shows long-term stability and maintains a current density of 10 mA cm⁻² for more than 12 h of continuous water splitting. The superior electrocatalytic performance should be ascribed to its unique 2D layered structure, which is favorable for ion diffusion and mass transportation; above all, the synergistic effect between SeO₃ anions and bimetallic centers could regulate its electronic structure, leading to enhanced electrocatalytic performance toward the OER.