Electrochemical deposition and properties of PbO2 + Co3O4 composites

Electrolysis of suspensions of Co₃O₄ particles in Pb²⁺-containing electrolytes has been used for depositing PbO₂ + Co₃O₄ composite layers on Ni rotating dise 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 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.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 α. At a fixed potential, j is roughly proportional to OH⁻ concentration. The PbO₂ + Co₃O₄ electrode performance is fairly stable at 25°C but declines with time at higher temperature.