Other version: http://jcp.aip.org/resource/1/jcpsa6/v124/i5/p054717_s1?view=fulltext
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Titles listSimultaneous in situ monitoring of surface and gas species and surface properties by modulation excitation...
Titles listSimultaneous in situ monitoring of surface and gas species and surface properties by modulation excitation...
Scientific Article
unige:14673 
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Simultaneous in situ monitoring of surface and gas species and surface properties by modulation excitation polarization-modulation infrared reflection-absorption spectroscopy: CO oxidation over Pt film |
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| Published in | Journal of Chemical Physics. 2006, vol. 124, no. 5, p. 54717-11 | |
| Abstract | A method for in situ monitoring of surface and gas species utilizing separately the difference and sum reflectivity of two polarizations, normal and parallel to the surface, measured by polarization-modulation infrared reflection-absorption spectroscopy is presented. Surface and gas-phase spectra were separately but simultaneously obtained from the reflectivities. The technique is combined with modulation excitation spectroscopy to further enhance the sensitivity, and a small-volume cell was designed for this purpose. CO oxidation over a 40 nm Pt film on aluminum was investigated under moderate pressure (atmospheric pressure, 5% CO, and 5%–40% O2) at 373–433 K. The surface species involved in the oxidation process and the gas-phase species, both reactant (CO) and product (CO2), could be simultaneously monitored and analyzed quantitatively. In addition, the reflectivity change of the sample during the reaction was assigned to a near-surface bulk property change, that is, surface reconstruction to the oxide phase. Under an O2-rich atmosphere, two reactive phases, denoted as low- and high-activity phases, were identified. A large amount of atop CO was observed during the low-activity phase, while the adsorbed CO completely disappeared during the high-activity phase. The presence of an infrared-inactive CO2 precursor formed by the reaction between surface oxide and gaseous CO during the high-activity phase was inferred. The desorption of the CO2 precursor is facilitated under a CO-rich atmosphere, most likely, by surface reconstruction to metallic Pt and a competitive adsorption of CO on the surface. | |
| Identifiers | DOI: 10.1063/1.2159484 | |
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| Citation (ISO format) | URAKAWA, Atsushi et al. Simultaneous in situ monitoring of surface and gas species and surface properties by modulation excitation polarization-modulation infrared reflection-absorption spectroscopy: CO oxidation over Pt film. In: Journal of Chemical Physics, 2006, vol. 124, n° 5, p. 54717-11. doi: 10.1063/1.2159484 https://archive-ouverte.unige.ch/unige:14673 |
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