Simultaneous Electrochemical Measurement of Oxygen Reduction and Pt Oxide Formation/Reduction on Pt Nanoparticle Surface

Using a rotating ring-disk electrode with shielding technique, oxygen reduction reaction (ORR) and surface oxide formation/reduction on Pt nanoparticles were successfully measured at the same time. The surface oxide coverage in presence of oxygen dissolved in electrolyte was found to be affected by concentration of the oxygen, indicating that the coverage measured using conventional voltammetric method under deaerated condition is not necessarily consistent with that when ORR proceeds. Analyses of relationship between the oxide coverage and the ORR kinetics revealed that the Pt oxide has little effect on the ORR kinetic on bare Pt surface. Hence, the oxide does not alter the adsorption energy of reaction intermediates very much whereas that blocks active sites for ORR.