The surface morphology of ion-selective membrane electrodes: Part 3. Studies on the Lead Ion-selective Membrane

Studies of the changes in the surface state of the ion-selective membrane and in the performance of the silver sulphide-lead sulphide (2:1) precipitate-based electrode are described. A scanning electron microscope was used to examine the surface of the electrode membrane. The results indicate that passivation of the lead-selective electrode caused by chemical and electrochemical oxidation is due to transformation of the lead sulphide at the membrane surface. The electrode surface becomes depleted in lead sulphide; lead sulphate crystals are formed during chemical oxidation with hydrogen peroxide, and lead oxide crystals during anodic oxidation.