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

Crystalline cobalt oxide nanoparticles (nc-CoOx) supported on ITO glass or Ni foam doped with 5 mol % crystalline iridium oxide nanoparticles (nc-IrOx) showed performances which are higher than those of nc-CoOx on ITO or Ni foam and nc-IrOx 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-CoOx particles intrinsically carry (CoO5)-O-III centers which become (CoO6)-O-IV centers upon application of positive potentials. The O vacancy in (CoO5)-O-III is transferred to (IrO6)-O-VI upon application of positive potentials, giving rise to the formation of (IrO5)-O-VI centers, which are proposed to be the highly active catalytic centers for water oxidation.