The behaviour of platinized-platinum and platinum-ruthenium electrodes in methanol solutions

Abstract

Measurements of the curves showing the dependence of the shift in the Pt/Pt electrode potential, after the introduction of methanol, upon pH of the solution and the potential at the moment of introduction of methanol, lead to the conclusion that the potentials of a Pt/Pt electrode, in methanol solutions, are determined by the adsorbed hydrogen. The presence of adsorbed hydrogen has been established from the charging curves and the potentiostatic curves of a platinum electrode measured after its contact with methanol. The analysis of these curves shows, also, that under definite conditions a predominant chemisorption of particles with the composition HCO occurs on platinized platinum in methanol solutions. The kinetics of methanol oxidation under non-steady-state and steady-state conditions have been studied and the difference in the mechanisms of the process on the bare platinum surface and on that covered with a stationary layer of chemisorbed substance, shown. The influence of pH of the solution, the dependence of the rate upon the potential and the kinetic characteristics of electro-oxidation of the chemisorption products, are used as possible criteria for the elucidation of the mechanism of the process. A hypothesis has been advanced, that on a bare surface the rate of the process is determined by dehydrogenation of the original alcohol molecules and under steadystate conditions-by the oxidation of the products of their chemisorption. In acid solutions the latter process may proceed by way of interaction with OH radicals. Some possible schemes of the oxidation process in alkaline solutions have been discussed. Composite electrolytic deposits of platinum and ruthenium, and of palladium and ruthenium with a small percentage of ruthenium, have been found to be extremely catalytically active in the reaction of methanol electro-oxidation.