The Retardation of Methanol Oxidation at a Platinum Electrode in an Acid Solution

Article abstract of DOI:10.1246/bcsj.61.3295

The rate retardation of the oxidation of methanol at the potential range of about 0.65-0.8 V vs. a reversible hydrogen electrode on a platinum electrode in 0.5 mol dm^-3 H2SO4 was studied.The rate retardation of the overall oxidation was caused by that of the oxidation, Reaction D, not via CO_ad.From the relationship among the rate of Reaction D, the CO_ad coverage, and the potentials, three types of rate retardation were found out: Type 1-Reaction D is not accelerated by the potential, and the rate of the reaction is determined by the CO_ad coverage and the methanol concentration.Type 2- the rate of Reaction D decreases at stationary CO_ad coverages as the oxidation is prolonged.Type 3- the rate decreases at CO_ad coverages close to the limiting value.It is proposed that Types 1 and 2 of the rate retardations take place when the adsorption of methanol molecules is rate-determining, and when the formaldehyde and formic acid formed from methanol are accumulated in the vicinity of the electrode, respectively.Type 3 of the rate retardation has been explained in a preceding paper in terms of the aggregate damaging effect of CO_ad.