title: SO2 adsorption on carbon-supported Pt electrocatalysts.
abstract: Adsorption of SO2 on a Pt/C catalyst typically used in proton exchange- membrane fuel cells (PEMFCs) has been investigated by temperature programmed desorption (TPD). SO2 concentrations in N2 were varied from 5 ppm to 1% (vol) and adsorption isotherms were determined at 25, 50, and 80 °C. Oxygen assisted (O-assisted) desorption experiments (i.e., successive TPD experiments following exposure to room temperature O2 after the first TPD event) produced an additional SO2 peak at a temperature higher than the initial SO2 peak. These two types of SO2 adsorption were identified as weakly adsorbed SO2 species desorbed between 140 and 200 °C, depending on concentration, and a strongly adsorbed, dissociated species. For the strongly adsorbed, dissociative species, (18)O2 isotope introduction during O-assisted desorption yielded ratios of 50%, 36%, and 14% for SO2 masses of 64, 66, and 68, respectively. The activation energy and kinetic constant of desorption are reported for weakly adsorbed SO2 at 1% and 20 ppm SO2 using the Polanyi-Wigner equation.
authors.affiliation: Department of Industrial Chemistry, Chiang Mai University, Thailand 50200.
authors.forename: K
authors.initials: K
authors.lastname: Punyawudho
authors.forename: J R
authors.initials: JR
authors.lastname: Monnier
authors.forename: J W
authors.initials: JW
authors.lastname: Van Zee