Electrocatalysis of anodic oxygen- transfer reactions. Ultrathin films of lead oxide on solid electrodes

Ultrathin films (ca. &le0.5 μm) of lead oxide, concluded to be PbO, were generated on the surfaces of Au, Pt, Ti, and GC electrodes during rapid voltammetric dissolution of thick films (> ca. 10-100 μm) of β-PbO2 deposited from acidic solutions containing Pb2+. These PbO films were stable at potential values > ca. 0.5V negative of the peak potential for cathodic stripping of bulk PbO2. Ultrathin films of PbO2 were produced, in turn, by anodization of the PbO films in Pb2+-free solutions. Results are emphasized here for the voltammetric and microscopic characterization of these thin films at Au electrodes. The formation of the stable PbO film during cathodic dissolution of thick PbO2 films is concluded to be the result of a deficiency of H+ in the interfacial region between the substrates and the porous thick oxide films. Ultrathin PbO films were oxidized to ultrathin PbO2 films during a positive potential scan and were determined to be electrocatalytically active for oxidation of dimethylsulfoxide (DMSO) at E > 1.5V vs. SCE when Bi3+ was present in the test solutions.