SO2 adsorption products on Pt nanoparticles as a function of electrode potential and oxidative properties of carrier gas: In situ sulfur K-edge XANES approach

• DOI: 10.1016/j.cattod.2012.08.024
• Publication Date: 2012-10-25T18:32:26Z
• Authors: Olga A. Baturina; Benjamin D. Gould; Paul A. Northrup; Karen E. Swider-L...
• Keywords: XANES; Reversible hydrogen electrode

Abstract In situ sulfur K-edge X-ray absorption near-edge structure spectroscopy is used to determine the nature of adsorbed SO 2 species from a SO 2 /O 2 gas mixture on carbon-supported Pt nanoparticles (Pt/VC). SO 2 was adsorbed onto electrodes held at 0.1, 0.5, 0.7 and 0.9 V vs. a reversible hydrogen electrode while flowing 1000 ppm SO 2 in O 2 through the working electrode (WE) compartment. SO 2 adsorption products from SO 2 /O 2 are compared to those from SO 2 /N 2 gas mixtures [Baturina, et al., Langmuir, 27 (2011) 14930]. The SO 2 adsorption products are found to be essentially the same at electrodes held at 0.5, 0.7 and 0.9 V. A major difference is observed at 0.1 V, where (bi)sulfate ions are generated in the presence of SO 2 in O 2 likely due to a reaction between SO 2 and H 2 O 2 formed as a byproduct of the oxygen reduction reaction in the hydrogen adsorption region. (Bi)sulfate generation on Pt/VC catalysts held at 0.1 V suggests that SO 2 may act as a peroxide radical scavenger at the PEM fuel cell cathode. Although impurities such as SO 2 and H 2 S usually promote hydrogen peroxide generation at the fuel cell cathodes, their detrimental effect may be diminished by their reaction with H 2 O 2 .