Products of SO2 Adsorption on Fuel Cell Electrocatalysts by Combination of Sulfur K-Edge XANES and Electrochemistry

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• 作者：Olga A. Baturina ; Benjamin D. Gould ; Anna Korovina ; Yannick Garsany ; Richard Stroman ; Paul A. Northrup
• 刊名：Langmuir
• 出版年：2011
• 出版时间：December 20, 2011
• 年：2011
• 卷：27
• 期：24
• 页码：14930-14939
• 全文大小：1052K
• 年卷期：v.27,no.24(December 20, 2011)
• ISSN：1520-5827

文摘

Electrochemical adsorption of SO₂ on platinum is complicated by the change in sulfur oxidation state with potential. Here, we attempt to identify SO₂ adsorption products on catalyst coated membranes (CCMs) at different electrode potentials using a combination of in situ sulfur K-edge XANES (X-ray absorption near-edge structure) spectroscopy and electrochemical techniques. CCMs employed platinum nanoparticles supported on Vulcan carbon (Pt/VC). SO₂ was adsorbed from a SO₂/N₂ gas mixture while holding the Pt/VC-electrode potential at 0.1, 0.5, 0.7, and 0.9 V vs a reversible hydrogen electrode (RHE). Sulfur adatoms (S⁰) are identified as the SO₂ adsorption products at 0.1 V, while mixtures of S⁰, SO₂, and sulfate/bisulfate ((bi)sulfate) ions are suggested as SO₂ adsorption products at 0.5 and 0.7 V. At 0.9 V, SO₂ is completely oxidized to (bi)sulfate ions. The identity of adsorbed SO₂ species on Pt/VC catalysts at different electrode potentials is confirmed by modeling of XANES spectra using FEFF8 and a linear combination of experimental spectra from sulfur standards. Results on SO₂ speciation gained from XANES are used to compare platinum鈥搒ulfur electronic interactions for Pt₃Co/VC versus Pt/VC catalysts in order to understand the difference between the two catalysts in terms of SO₂ contamination.