Effect of anions on the electrochemical behavior of Pb electrodes in alkaline solutions and on the anodic oxide film properties

Studies regarding the effect of anions such as SO42-, OAc-, NO3- and Cl- ions as additional electrolytes (0.1 M each) on the electrochemical behavior of Pb electrodes in 0.1 M NaOH solution at 80 degrees C are presented. These anions have been found to exert a marked effect on the cyclic voltammetric behavior of the Pb electrode, anodic film formation kinetics, morphology of the anodic films and on its photoelectrochemical responses. Except in NaOH and NaOH + Na2SO4 electrolytes, the anodic film formed on the Pb electrode tends to dissolve or fall off from the electrode surface at higher potentials. A reasonably thick anodic oxide film could be obtained only at lower potentials in all the electrolytes. The anodic films obtained at -0.5 V vs. SCE consist of mainly the alpha-PbO phase except in chloride ion containing solution where the beta-PbO phase is formed. The photoelectrochemical responses of the anodic films thus obtained were tested in Fe(CN)(6)(3-/4-) redox electrolyte. An interesting finding is that among added anions, sulfate ion is the most effective for preparing photoelectrochemically active films. The film formed at higher potential:; in sulfate ion containing solution had a strong 110 orientation, a highly porous surface morphology and exhibited the highest quantum efficiency for anodic photocurrent generation, which amounted to 60%. (C) 1997 Elsevier Science S.A.