"d-electron interactions" induced CoV2O6-Fe-NF for efficient oxygen evolution reaction.

The investigation of cost-effective, highly efficient, and environmentally friendly non-noble-metal-based electrocatalysts is imperative for oxygen evolution reactions (OER). Herein, CoV2O6 grown on nickel foam (NF) was selected as the fundamental material, and Fe2+ is introduced through a simple Fe3+ immersion treatment to synthesize CoV2O6-Fe-NF. Fe2+ is transformed into high oxidation state Fe(2+δ)+ due to interactions between the 3d electrons of transition metals. In situ Raman spectroscopy analysis reveals the specific process of OER in the presence of Fe(2+δ)+. Being in a higher oxidation state, Fe(2+δ)+ provides more active sites, which is beneficial for the reaction between water molecules and the reactive sites of the electrocatalyst, ultimately enhancing the accelerated OER process. CoV2O6-Fe-NF exhibited an overpotential of only 298 mV at 100 mA cm-2 in 1 M KOH electrolyte, which is lower than that of CoV2O6-NF (348 mV), as well as the comparative samples: Fe-NF (390 mV) and NF (570 mV). The exploration of high performance, triggered synergistically by the cooperative effect of transition metal 3d electrons, provides insights into the design of transition metal electrocatalysts for highly efficient OER.