Three-Dimensional Honeycomb-Like Cu0.81Co2.19O4 Nanosheet Arrays Supported by Ni Foam and Their High Efficiency as Oxygen Evolution Electrodes.

We prepare three-dimensional honeycomb-like Cu0.81Co2.19O4 nanosheet arrays supported by Ni foam via electrochemical codeposition of cobalt and copper hydroxides on Ni foam followed by thermal oxidation. The codeposition with Cu changes the morphology of the cobalt hydroxide deposit to form honeycomb-like nanostructures, significantly decreasing the onset potential for oxygen evolution. The Cu0.81Co2.19O4 anode displays an exceptionally low overpotential of 290 mV at a current density of 10 mA cm-2 in 1 M KOH, and an anion-exchange membrane water electrolysis cell employing the above anode achieves a current density of 100 mA cm-2 at 1.68 V in 0.1 M KOH.