Electrocatalytic oxidation of methanol and carbon monoxide at platinum in protic ionic liquids

Abstract

Oxidation of H2O, CO and CH3OH was investigated at Pt as a function of temperature in the protic ionic liquid diethylmethylammonium trifluoromethanesulfonate. Trace H2O oxidation in the ionic liquid results in coverage of the Pt with adsorbed oxides. Increasing the temperature significantly reduces the potential at which this reaction occurs. CH3OH and CO oxidation kinetics increased significantly with increasing temperature and oxidation of each species coincided with coverage of the Pt surface by the oxide. These observations indicate that surface oxides are required for complete oxidation of CH3OH to CO2 in the protic ionic liquid, in a similar way to that observed in conventional aqueous electrolytes. While the overpotential for CH3OH oxidation was drastically higher than that observed in purely aqueous electrolytes, it decreased with increasing water content of the ionic liquid. The results described here have implications for the development of protic ionic liquid electrolyte fuel cells and these implications are discussed. Keywords: Direct methanol fuel cells, Electrocatalysis, Protic ionic liqui