CATHODIC REDUCTION OF OXYGEN AND HYDROGEN PEROXIDE ON PLATINUM, PALLADIUM AND IRIDIUM SMOOTH ELECTRODES

TL;DRAbstract

Polarization curves in acid, neutral and alkaline solutions were drawn by potentiostatic method, for O and H2O2 reduction processes and for H2O2 oxidation process, on Pt, Ir and Pd electrodes. These curves could be classified as follows: those whose slopes are 0.030 to 0.12, and those with slopes higher than 0.12. The former can be explained through already proposed mechanisms (addition of one electron or one atom of H to an adsorbed O molecule; or addition of one electron to an HO2 adsorbed radical). The slopes higher than 0. 12 involve a slow O or HO2 radical adsorption which becomes kinetically determining first of all for Ir in both acid and neutral solutions. For Pd in H2SO4 solution and for Pt in HCl solution the O adsorption process is very slow, essentially due to the complexing action of the solution with resulting formation of surface complexes which engage the metal atoms, thus preventing or reducing the formation of adsorbed oxide.

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