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SO2 adsorption on carbon-supported Pt electrocatalysts
K Punyawudho1, J R Monnier, J W Van Zee
1Department of Industrial Chemistry, Chiang Mai University, Thailand 50200.
Langmuir : the ACS Journal of Surfaces and Colloids
|February 8, 2011
Summary
Sulfur dioxide (SO2) adsorption on platinum/carbon (Pt/C) catalysts in proton exchange-membrane fuel cells (PEMFCs) reveals two species: weakly adsorbed SO2 and strongly adsorbed, dissociated SO2. Oxygen-assisted desorption helps differentiate these adsorption behaviors.
Area of Science:
- Catalysis
- Electrochemistry
- Surface Science
Background:
- Proton exchange-membrane fuel cells (PEMFCs) are crucial for clean energy conversion.
- Sulfur dioxide (SO2) is a common contaminant that can poison fuel cell catalysts.
- Understanding SO2 adsorption on platinum/carbon (Pt/C) catalysts is vital for improving PEMFC durability.
Purpose of the Study:
- To investigate the adsorption mechanisms of SO2 on Pt/C catalysts.
- To differentiate between various SO2 adsorption states.
- To quantify the kinetics and thermodynamics of SO2 desorption.
Main Methods:
- Temperature Programmed Desorption (TPD) was employed to study SO2 adsorption.
- SO2 concentrations were varied from 5 ppm to 1% (vol) at different temperatures (25, 50, 80 °C).
- Oxygen-assisted (O-assisted) desorption and (18)O2 isotope tracing were used to identify adsorption species.
Main Results:
- Two distinct SO2 adsorption states were identified: weakly adsorbed SO2 (140-200 °C) and a strongly adsorbed, dissociated species.
- O-assisted desorption revealed a higher temperature SO2 peak, indicating stronger adsorption.
- (18)O2 isotope experiments confirmed the dissociative nature of the strong adsorption state.
Conclusions:
- Pt/C catalysts exhibit complex SO2 adsorption behavior with both reversible and dissociative pathways.
- The presence of strongly adsorbed, dissociated SO2 can significantly impact catalyst performance in PEMFCs.
- Kinetic parameters for weakly adsorbed SO2 were determined, providing insights for catalyst design and operation.
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