Effect of O2 on the Adsorption of SO2 on Carbon-Supported Pt Electrocatalysts

• Published in: Langmuir 2011-06, Vol.27 (12), p.7524-7530
• Main Authors: Punyawudho, K, Ma, S, Van Zee, J. W, Monnier, J. R
• Format: Article
• Language: English
• Subjects: Catalysis; Chemistry; Electrochemistry; Exact sciences and technology; General and physical chemistry; Interfaces: Adsorption, Reactions, Films, Forces; Kinetics and mechanism of reactions; Surface physical chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la2000377

Adsorption of SO2 in the presence of O2 on Pt/C catalysts often used as electrocatalysts has been investigated by temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). The amounts of SO2 adsorption on Pt/C in the presence of O2 were much higher than those in the absence of O2 (SO2–N2) and from the carbon support (Vulcan XC-72) alone. Adsorption is dependent on oxygen concentration over the range 0–20% but reaches saturation at 20% O2. The spillover of SO2 from Pt to the carbon support has been proposed for 10, 20, and 40% Pt loadings, characterized by desorption temperatures of approximately 150 and 260 °C for SO2 adsorbed on Pt and carbon, respectively. Adsorbed Pt–S, C–S, C–SO x , and Pt–SO4 species were identified by XPS as S-containing species on both Pt and carbon. Both TPD and XPS indicate that the carbon support plays a major role in SO2 adsorption, primarily as SO x (x = 3, 4). The bonding of S and SO x on the carbon support was strong enough that back diffusion to the Pt surface did not occur.