A systematic investigation of the mechanistic and electrocatalytic properti
es of O-2 evolution from acidic solutions was conducted using Ti/RuO2(x) Co3O4(1 - x) anodes prepared by thermal decomposition (470 degreesC), with
x varied between 0 and 100% mel. Kinetics were studied by current-potential
curves recorded under quasi-stationary conditions and reaction order deter
mination. At low overpotentials, a Tafel slope of about 30 mV was found for
materials having a 30-80%, mol RuO2 content. A reaction mechanism has been
proposed accounting for the composition dependence of the Tafel slope and
the order of reaction at constant potential. It has been concluded that mix
ed oxides bring about an increase in the real electrocalalytic activity, wh
ich can be attributed to the synergetic or edge effect between the oxide co
mponents. A mechanism for the anodic dissolution of Co3O4 is proposed. (C)
2001 Elsevier Science Ltd. All rights reserved.