Direct growth of holey Fe3O4-coupled Ni(OH)2 sheets on nickel foam for the oxygen evolution reaction

The oxygen evolution reaction (OER) is a half-reaction of water electrolysis, and the OER performance of an electrocatalyst is significantly related to its energy conversion efficiency. Due to their high OER activity, transition metal-based nanomaterials have become potential low-cost substitutes for Ir/Ru-based OER electrocatalysts in an alkaline environment. Herein, holey Fe3O4-coupled Ni(OH)2 sheets (Ni(OH)2-Fe H-STs) were easily achieved by a simple mixed-cyanogel hydrolysis strategy. The two-dimensional (2D) Ni(OH)2-Fe H-STs with ca. 1 nm thickness have a high specific surface area, abundant unsaturated coordination atoms, and numerous pores, which are highly favorable for electrocatalytic reactions. Meanwhile, the introduction of Fe improves the conductivity and regulates the electronic structure of Ni. Due to their special structural features and synergistic effect between the Fe and Ni atoms, Ni(OH)2-Fe H-STs with an optimal Ni/Fe ratio show excellent OER activity in a 1 M KOH solution, which significantly exceeds that of the commercial RuO2 nanoparticle electrocatalyst. Furthermore, Ni(OH)2-Fe H-STs can be grown on nickel foam (NF), and the resulting material exhibits enhanced OER activity, such as a small overpotential of 200 mV and a small Tafel slope of 56 mV dec−1, than that of Ni(OH)2-Fe H-STs without NF.