Surface Electrochemical Modification of a Nickel Substrate to Prepare a NiFe-based Electrode for Water Oxidation

The slow kinetics of water oxidation greatly jeopardizes the efficiency of water electrolysis for H₂ production. Developing highly active water oxidation electrodes with affordable fabrication costs is thus of great importance. Herein, a Ni^II Fe^III surface species on Ni metal substrate was generated by electrochemical modification of Ni in a ferrous solution by a fast, simple, and cost-effective procedure. In the prepared Ni^II Fe^III catalyst film, Fe^III was incorporated uniformly through controlled oxidation of Fe^II cations on the electrode surface. The catalytically active Ni^II originated from the Ni foam substrate, which ensured the close contact between the catalyst and the support toward improved charge-transfer efficiency. The as-prepared electrode exhibited high activity and long-term stability for electrocatalytic water oxidation. The overpotentials required to reach water oxidation current densities of 50, 100, and 500 mA cm^-2 are 276, 290, and 329 mV, respectively.