Electrolysis of suspensions of Co3O4 particles in Pb2+-containing electrolytes has been used for depositing PbO2 + Co3O4 composite layers on Ni rotating disc anodes. A sufficiently high angular speed of the electrode is necessary to obtain layers of homogeneous thickness and Co3O4 concentration. The volume fraction of Co3O4 particles in the deposit cu reaches a limiting value of ca. 0.1 when the volume fraction of particles in suspension C exceeds 0.008. The current density j has little 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 have been studied as electrode materials for the oxygen evolution reaction (mainly in NaOH solution). The overpotential and Tafel slope decrease upon increasing alpha. At a fixed potential, j is roughly proportional to OH- concentration. The PbO2 + Co3O4 electrode performance is fairly stable at 25 degrees C but declines with time at higher temperature.