Effect of the partial replacement of Fe by Ni and/or Mn on the electrocatalytic activity for oxygen evolution of the CoFe2O4 spinel oxide electrode

The study of the electrochemical behaviour of mixed spinel oxide electrodes, obtained by the partial replacement of Fe by Ni and/or Mn in the cobalt ferrite CoFe2O4 is presented. The electrodes were prepared by brush painting of iron substrates with a suspension of the respective oxide, prepared by solid-state reaction. The influence of the substituent on the electrodes electrocatalytic activity towards the OER is analysed in terms of the kinetic parameters obtained by steady state measurements and the cationic distribution proposed for the oxides. The data show that the introduction of Ni brings about the presence of Co3+ tetrahedrally coordinated in addition to the Co3+/Co2+ couple in octahedral sites, giving rise to a better electrocatalyst for the OER. In contrast the presence of Mn produces electrodes with lower catalytic activity. (C) 2002 Elsevier Science Ltd. All rights reserved.