ELECTROCHEMICAL DEPOSITION AND PROPERTIES OF PBO2+CO3O4 COMPOSITES

Electrolysis of suspensions of Co3O4 particles in Pb2+-containing elec trolytes has been used for depositing PbO2 + Co3O4 composite layers on Ni rotating disc anodes. A sufficiently high angular speed of the ele ctrode is necessary to obtain layers of homogeneous thickness and Co3O 4 concentration. The volume fraction of Co3O4 particles in the deposit cu reaches a limiting value of ca. 0.1 when the volume fraction of pa rticles in suspension C exceeds 0.008. The current density j has littl e effect on alpha as long as it is in the range 1 to 20 mA cm(-2); if j increases further, alpha decreases. PbO2 + Co3O4 composite layers ha ve been studied as electrode materials for the oxygen evolution reacti on (mainly in NaOH solution). The overpotential and Tafel slope decrea se upon increasing alpha. At a fixed potential, j is roughly proportio nal to OH- concentration. The PbO2 + Co3O4 electrode performance is fa irly stable at 25 degrees C but declines with time at higher temperatu re. (C) 1997 Elsevier Science S.A.