Electrolysis of suspensions of Co 3 O 4 particles in Pb 2 + -containing electrolytes has been used for depositing PbO 2 + Co 3 O 4 composite layers on Ni rotating disc anodes. A sufficiently high angular speed of the electrode is necessary to obtain layers of homogeneous thickness and Co 3 O 4 concentration. The volume fraction of Co 3 O 4 particles in the deposit α 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 α as long as it is in the range 1 to 20 mA cm - 2 ; if j increases further, α decreases.PbO 2 + Co 3 O 4 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 α. At a fixed potential, j is roughly proportional to OH - concentration. The PbO 2 + Co 3 O 4 electrode performance is fairly stable at 25°C but declines with time at higher temperature.