SO2 Adsorption on Carbon-Supported Pt Electrocatalysts

Abstract

Adsorption of SO2 on Pt/C catalysts was investigated by temperature programmed desorption (TPD). SO2 concentrations were varied from 5 ppm to 1% (vol) and adsorption isotherms were determined at 25, 50, and 80{degree sign}C. Desorption temperatures of SO2 increased as adsorption temperatures of adsorption were increased, and SO2 concentrations were lowered. TPD experiments following exposure to room temperature O2 (after the first TPD event) gave an additional SO2 peak at temperatures higher than the initial SO2 peak, thus identifying two different types of SO2 adsorption. Two adsorption energies were indentified as weak and strong adsorption. 18O2 isotope was introduced during oxygen titration to verify adsorption mechanism and dissociative species. Langmuir isotherms were plotted and led to isosteric adsorption of SO2 for weak and strong adsorption.