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 C l- 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 th e cyclic voltammetric behavior of the Pb electrode, anodic film format ion kinetics, morphology of the anodic films and on its photoelectroch emical responses. Except in NaOH and NaOH + Na2SO4 electrolytes, the a nodic film formed on the Pb electrode tends to dissolve or fall off fr om the electrode surface at higher potentials. A reasonably thick anod ic oxide film could be obtained only at lower potentials in all the el ectrolytes. The anodic films obtained at -0.5 V vs. SCE consist of mai nly the alpha-PbO phase except in chloride ion containing solution whe re 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, sulfat e ion is the most effective for preparing photoelectrochemically activ e films. The film formed at higher potential:; in sulfate ion containi ng solution had a strong 110 orientation, a highly porous surface morp hology and exhibited the highest quantum efficiency for anodic photocu rrent generation, which amounted to 60%. (C) 1997 Elsevier Science S.A .