Effect of temperature on the methanol oxidation at supported Pt and PtRu catalysts in alkaline solution

Abstract

The effect of temperature on the kinetics of methanol oxidation on supported 47.5 wt% Pt, 54 and 33.5 wt% Pt/Ru catalysts was studied in 0.1 M NaOH at 295, 313 and 333 K using thin-film rotating disk electrode (RDE) method. The catalysts were characterized by ex situ STM prior to the voltammetric studies. It was found that the activity of those catalysts for methanol oxidation was determined by a delicate balance between the surface coverage by COad and by OHad species. Significantly faster kinetics at higher temperatures clearly indicates that methanol oxidation at the catalysts studied is highly activated process. The highest effect of temperature is obtained at the least active Pt catalyst which has the highest activation energy. On the contrary, the smallest temperature effect is detected on the most active Pt3Ru2 catalyst having the lowest activation energy. These phenomena have been explained by the important role of the adsorption energies of both reactive intermediates (COad and OHad).