New active spinel-type MxCo3-xO4 films for electro-catalysis of oxygen evolution

Spinel-type binary oxides of Co with Cu, Ni, or Mn were prepared at 350 deg rees C using a precipitation method and reproduced in the film forms on pre treated Ni-supports by an oxide-slurry painting technique. The study showed that the introduction of Cu/or Ni (0.25 - 1.0 mel) in the Co3O4-matrix inc reased the electrochemically arrive area as well as the apparent electrocat alytic activity showing maximum at 0.5 mol metal doping. At the overpotenti al, 350 mV, in 1M KOH (25 degrees C), the apparent electrocatalytic activit y of the Cu0.5Co2.5O4 electrode was approximate to 2 times higher than that of the Ni0.5Co2.5O4 electrode. Mn-substitutions were observed to be detrim ental from the electrocatalysis stand-point. The order (p = Ij and Tafel sl ope (b(1) = 2.303RT/F)for the O-2 evolution reaction were approximately the same for each electrocatalyst regardless of the nature and amount of the m etal being doped.