The Interaction of Carbon Monoxide With Nitric Oxide and Hydrogen on Platinum
Park, Young Oun
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Permalink
https://hdl.handle.net/2142/69751
Description
Title
The Interaction of Carbon Monoxide With Nitric Oxide and Hydrogen on Platinum
Author(s)
Park, Young Oun
Issue Date
1985
Department of Study
Chemical Engineering
Discipline
Chemical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Date of Ingest
2014-12-15T19:54:22Z
Keyword(s)
Engineering, Chemical
Abstract
Reaction of NO, CO, and H(,2), and interaction between NO and CO and between CO and H(,2) on Pt(410) have been investigated using Temperature Programmed Desorption. Pt(410) is found to be unusually reactive in decomposition of NO even at 120 K, as evidenced by desorption of N(,2)O below 150 K. At low exposures of NO, only the formation of N(,2) is observed. The formation of N(,2)O if found to take place via a precursor mechanism, i.e. reaction between adsorbed nitrogen atoms and weakly bound NO molecules. Annealing experiment indicates that a surface reconstruction takes place during heating cycle of an NO adlayer at 120 K. Pt(410) is also found to be unusually reactive in decomposition of CO. This decomposition process complicates the desorption spectra of CO in room temperature study. Adsorption of CO at 120 K is almost identical to the room temperature study, except the appearance of the (alpha)(,0) and (alpha)(,1) peaks.
Interaction of NO and CO on Pt(410) at 120 K provides additional evidence for the unusual reactivity of Pt(410). Coadsorption of NO and CO on Pt(410) at 120 K produces mainly two products, N(,2)O and CO(,2), as well as some desorption of (alpha)(,0)-CO and (alpha)(,1)-CO. Desorption of CO(,2) exhibits the behavior of a surface explosion, whose peak width at half maximum (PWHM) is as narrow as 10 K. The surface explosion is postulated to be associated with a surface reconstruction which is initialized by the reaction between the atomic oxygen and adsorbed CO.
In the study of adsorption of hydrogen on Pt(410), the behavior of hydrogen at 120 K is markedly different from that of hydrogen at 273 K. In the 120 K study, Pt(410) appears to undergo a phase transition into a more open phase upon adsorption of hydrogen, which traps tremendously large amount of hydrogen forming a "subsurface" hydrogen layer. Desorption of hydrogen after adsorption at 273 K follows a second order process with an activation energy of 18.2 kcal/mole and a preexponential of 3.4 x 10('15)/sec.
In coadsorption of CO and H(,2) both at 300 K and 120 K, CO blocks H(,2) adsorption and replaces preadsorbed H(,2). CO is also found to weaken the binding state of chemisorbed H(,2). Behavior of coadsorbed CO and H(,2) is found to be similar to that of coadsorbed CO and NO.
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