Preferential CO oxidation in a large excess of hydrogen on Pt₃Sn surfaces

• Published in: Journal of catalysis 2011-03, Vol.278 (2), p.239-245
• Main Authors: Dupont, C, Delbecq, F, Loffreda, D, Jugnet, Y
• Format: Article
• Language: English
• Subjects: absorption; active sites; alloys; Carbon monoxide; carbonates; Catalysis; catalysts; catalytic activity; Chemical Sciences; Chemistry; Environment and Society; Environmental Sciences; Exact sciences and technology; General and physical chemistry; Hydrogen; infrared spectroscopy; mass spectrometry; Oxidation; temperature; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; tin
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2010.12.012

An experimental evaluation, under realistic conditions, of the catalytic properties of a Pt₃Sn(111) model catalyst in CO oxidation under excess of hydrogen is reported in this study. From a structural point of view, two different surface terminations are available in this alloy, viz. (2×2) and (3×3)R30°, differing by their tin concentration and Pt–Sn local structural arrangements in the uppermost layers, thus offering specific active sites for the reaction to proceed. In this study, mass spectrometry and polarization modulation infrared reflection absorption spectroscopy measurements (PM-IRRAS) have been performed at near ambient pressure on both surfaces of the alloy and compared to those obtained on Pt(111) used as a reference. The presence of hydrogen promotes the rate of CO oxidation on the three surfaces. The influence of tin is remarkable, increasing the catalytic activity of Pt atoms by one order of magnitude. With the exception of CO, no other species such as formyls or carbonates are observed on the surface by IR spectroscopy in the range of temperature (293–425K) investigated.