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 grow two-dimensional cobalt-iron hydroxide (CoFe-OH) nanosheets on nickel foam substrates and deposit FeOOH nanoparticles in a rapid and scalable wet chemical approach. The CoFe-OH@FeOOH nanocomposite features abundant active sites and high surface area, allowing fast kinetics for electrochemical water splitting. The electrode has a low overpotential value of 200 mV at 50 mA cm−2 for oxygen evolution. When used as both anode and cathode for overall water splitting, CoFe-OH@FeOOH provides 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 may offer a new direction for designing efficient electrodes for energy conversion applications.