The potentials of mixed electrodes of corrodible metal and metal oxide

Abstract The electrode potential of oxide-covered metals and the mixed electrode potential of corrodible metals contacting with metal oxides are discussed in view of ionic and electronic transfer processes across the electrode interfaces. The oxide-covered metal electrode stands either at the potential of metal oxide formation or at the flat band potential of metal oxide. The mixed electrode of a corrodible metal and a metal oxide shifts its metallic corrosion potential toward the flat band potential of the oxide in the cathodic direction if the oxide is of the n-type, or in the anodic direction if the oxide is of the p-type. Photoexcitation of contacting oxides makes it possible for the anodic oxygen evolution to occur on the n-type oxides and for the cathodic hydrogen evolution to occur on the p-type oxides. It is suggested that the corrosion probability of metals reduces with the n-type oxides, whereas it increases with the p-type oxides.