Highly Active Three‐Dimensional NiFe/Cu 2 O Nanowires/Cu Foam Electrode for Water Oxidation

Water splitting is of paramount importance for exploiting renewable energy‐conversion and ‐storage systems, but is greatly hindered by the kinetically sluggish oxygen evolution reaction (OER). In this work, a three‐dimensional, highly efficient, and durable NiFe/Cu 2 O nanowires/Cu foam anode (NiFe/Cu 2 O NWs/CF) for water oxidation in 1.0  m KOH was developed. The obtained electrode exhibited a current density of 10 mA cm −2 at a uniquely low overpotential of η =215 mV. The average specific current density ( j s ) was estimated, on the basis of the electrocatalytically active surface area, to be 0.163 mA cm −2 at η =310 mV. The electrode also displayed a low Tafel slope of 42 mV decade −1 . Moreover, the NiFe/Cu 2 O NWs/CF electrode could maintain a steady current density of 100 mA cm −2 for 50 h at an overpotential of η =260 mV. The outstanding electrochemical performance of the electrode for the OER was attributed to the high conductivity of the Cu foam and the specific structure of the electrode with a large interfacial area.