Low Overpotential Overall Water Splitting by a Cooperative Interface of Cobalt-Iron Hydroxide and Iron Oxyhydroxide

Abstract

Interface engineering is a powerful strategy for modulating electronic structure and enhancing intrinsic activity of electrocatalysts for water splitting. Here, we grew two-dimensional (2D) cobalt iron hydroxide (CoFe-OH) nanosheets on nickel foam substrates and deposited FeOOH nanoparticles in a rapid and scalable wet chemical approach. The CoFe-OH@FeOOH nanocomposite features plenty of abundant active sites and high surface area, allowing fast kinetics in an electrochemical water splitting. The new electrode reveals a low overpotential value of 200 mV at 50 mA cm−2 for oxygen evolution reaction (OER). When used as both anode and cathode for overall water splitting, CoFe-OH@FeOOH boosted a low cell voltage of 1.56 V to deliver 10 mA cm−2 current density. The synergistic activity is presumed to be from the seamless interface of CoFe-OH and FeOOH, improving conductivity and mass transfer. We envision that this simple approach offers a new direction for designing efficient electrodes for energy conversion and storage.