Amorphous NiFe(oxy)hydroxide nanosheet integrated partially exfoliated graphite foil for high efficiency oxygen evolution reaction

Abstract

The requirements for large-scale industrial electrolytic water splitting have motivated investigations of inexpensive and stable oxygen evolution catalysts which would provide high current densities (>500 mA cm⁻²) at low overpotentials. Herein we develop a scalable electrodeposition route to fabricate amorphous nickel–iron(oxy)hydroxide nanosheets directly onto a 3D partially exfoliated graphite foil electrode. The integrated electrode combines the high OER catalytic activity of NiFe-based materials and the excellent electric conductivity of the carbon substrate, while facile ion transport and gaseous product (O₂) diffusion are guaranteed by its hierarchical structure. The electronic structure of the Ni catalytic center, which shows critical effects in determining the catalytic activity, can be controlled through Fe incorporation and/or tuning the electrodeposition potential window. The optimal electrode catalyzes the OER process with a low overpotential of 214 mV to reach 10 mA cm⁻² current density in 1 M KOH. The Tafel slope is as small as 21 mV dec⁻¹ so it is capable of delivering high current densities of 500 mA cm⁻² at an overpotential of only 251 mV. The OER can be prolonged to 100 h at 10 mA cm⁻² and 48 h at 500 mA cm⁻². The composite shows great potential towards large-scale and long-term practical applications.