Defect-Rich NiCeOx Electrocatalyst with Ultrahigh Stability and Low Overpotential for Water Oxidation

For the utilization of renewable energy resources to become widespread, efficient energy-storage devices must be developed. Electrocatalysts for the oxygen evolution reaction (OER) are needed for a wide variety of such devices, including fuel cells, metal–air batteries, and photoelectrochemical cells. Here we demonstrate a defect-rich NiCeOx layer, directly synthesized on a Ni substrate through a simple two-step dip-coating/annealing process, as a highly active and stable OER catalyst made from earth-abundant materials. With a low overpotential of 295 mV at 10 mA/cm2 and a stability of over 200 h, NiCeOx boasts one of the best performances reported in the literature. This good performance is a result of the large number of oxygen vacancy defects introduced into NiCeOx by the diffusion of Ni from the Ni substrate into a deposited CeOx film during the annealing step. The oxygen vacancy defects not only supply an abundance of active sites but also decrease the mass-transfer resistance, resulting in the large electrochemically active surface area and high OER performance. This work demonstrates the potential of developing defect-rich Ce-containing materials as robust OER catalysts.