HYDROGEN ADSORPTION-DESORPTION AND OXIDE FORMATION-REDUCTION ON POLYCRYSTALLINE PLATINUM IN UNBUFFERED AQUEOUS-SOLUTIONS

The properties of microelectrodes are exploited to characterise hydrogen adsorption-desorption and oxide formation-reduction at polycrystalline platinum in several aqueous electrolytes, especially unbuffered aqueous media including water without the addition of electrolyte. In unbuffered solutions, the peaks for hydrogen adsorption-desorption on a cyclic voltammogram are separated by several hundred millivolts. This separation results principally from pH changes within the solution close to the electrode, induced by the surface reactions themselves, although there is also a contribution from the slow kinetics of the electron-transfer processes. The contribution from the irreversibility of the electron-transfer reactions has been estimated using rapid-scan voltammetry in both acid and alkaline solutions. The influence of the mass-transport regime on the response is also discussed.