An in situ attenuated total reflection-surface enhanced infrared absorption spectroscopic study of enhanced methanol electro-oxidation activity on carbon-supported Pt nanoparticles by poly(vinylpyrrolidone) of different molecular weights

The effect of the commonly used 55,000 Mw (PVP55) and a heavier chain of 360,000 Mw (PVP360) on commercial 40 wt% Pt/C were probed using electrochemical methods and in situ SEIRAS experiments during the MOR and related gaseous CO oxidation. The polymer-modified samples exhibited an enhanced long-term CO tolerance with a small hindrance to the intrinsic activity of Pt/C. Increased water adsorption in the presence of polymer was observed to coincide with the oxidation of adsorbed CO and was related to the desorption of the surface-bound carbonyl of PVP via in situ SEIRAS. The notable differences between the adsorbate trends are indicative of adsorbed polymer interactions with the surface, but more interestingly is the strong dependence of the polymer molecular weight Mw that led to qualitatively different behavior. Understanding the effects of adsorbed PVP on electrocatalytic reactions is of fundamental and practical importance due to its widespread use in synthesized NPs targeted for fuel cell applications.