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 NiII FeIII 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 NiII FeIII catalyst film, FeIII was incorporated uniformly through controlled oxidation of FeII cations on the electrode surface. The catalytically active NiII 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.