Cobalt Oxide Electrode Doped with Iridium Oxide as Highly Efficient Water Oxidation Electrode

Crystalline cobalt oxide nanoparticles (nc-CoO_<i>x</i>) supported on ITO glass or Ni foam doped with 5 mol % crystalline iridium oxide nanoparticles (nc-IrO_<i>x</i>) showed performances which are higher than those of nc-CoO_<i>x</i> on ITO or Ni foam and nc-IrO_<i>x</i> on a rotating glassy carbon disc electrode or Ni foam. The initial Co^III and Ir^IV become Co^IV and Ir^VI upon applying positive potentials. The nc-CoO_<i>x</i> particles intrinsically carry Co^IIIO₅ centers which become Co^IVO₆ centers upon application of positive potentials. The O vacancy in Co^IIIO₅ is transferred to Ir^VIO₆ upon application of positive potentials, giving rise to the formation of Ir^VIO₅ centers, which are proposed to be the highly active catalytic centers for water oxidation