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Electrocatalysis of Anodic Oxygen‐Transfer Reactions: Application of an Electrochemical Quartz Crystal Microbalance to a Study of Pure and Bismuth‐Doped Beta‐Lead Dioxide Film Electrodes
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1990
Year
Materials ScienceOxygen Reduction ReactionEngineeringBattery Electrode MaterialsSurface ElectrochemistrySurface ScienceCatalysisAu‐film ElectrodesChemistryThin FilmsAnodic Oxygen‐transfer ReactionsElectrochemical ProcessElectrode Reaction MechanismTheoretical ElectrochemistrySurface MassElectrochemistryElectrochemical Surface Science
Ratios of the change in surface mass corresponding to a change in charge were determined for the electrodeposition of thin films of pure and Bi‐doped at Au‐film electrodes in , using an electrochemical quartz microbalance. The value obtained for pure films is in good agreement with the theoretical value of 1.24 mg C−1. A larger value, , obtained for the Bi‐doped films, is concluded to result from the co‐deposition of some with Bi(V) in the mixed‐oxide film. Bismuth(III) was determined to be anodically adsorbed as Bi(V) at pure surfaces for vs. with in and in . The electrodes with adsorbed Bi(V) are active for various anodic oxygen‐transfer reactions, including the oxidations of Mn(II) to and DMSO to . Experimental results are interpreted to be consistent with a mechanism proposed previously, in which the Bi(V) sites have a lower overpotential for anodic discharge of to produce . It has been proposed that adsorbed hydroxyl radicals (.OHads) generated in the evolution mechanism are consumed by oxygen‐transfer steps, required in many oxidation processes.