Temperature-programmed desorption study on NO on Pt particles supported on. alpha. -Al sub 2 O sub 3 (0001)

Journal Article · Thu Mar 09 00:00:00 EST 1989 · Journal of Physical Chemistry; (USA)

DOI:https://doi.org/10.1021/j100342a057· OSTI ID:7167336

Altman, E I; Gorte, R J ^[1]

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1. Univ. of Pennsylvania, Philadelphia (USA)

The adsorption and dissociation of NO on Pt/{alpha}-Al{sub 2}O{sub 3}(0001) were studied as a function of Pt particle size by using temperature-programmed desorption (TPD). Samples were prepared by vapor depositing varying amounts of Pt onto the substrate at 300 K in vacuum, and the average Pt particle size was estimated from the surface area measured by using the CO adsorption uptake and the amount of metal deposited as measured by a quartz crystal film thickness monitor. On Pt particles larger than 4.0 nm, the results were similar to those obtained on Pt foils and some stepped crystals. More than 80% of the NO that was adsorbed at 300 K dissociated during TPD, with N{sub 2} desorbing in a sharp peak at 460 K. As the particle size decreased, the fraction of NO that dissociated decreased, and a second N{sub 2} peak was observed in TPD at 540 K. This peak at 540 K was the only N{sub 2} desorption feature observed on the smallest particles (<2.0 nm), and only 45% of the NO dissociated during TPD on these samples. Using coadsorption of {sup 15}NO with low coverages of CO followed by monitoring CO{sub 2} formation during TPD, we found that the N{sub 2} desorption peaks at both 460 and 540 K are dissociation-rate limited. Therefore, smaller particles appear to be much less active for NO dissociation than larger particles. An additional conclusion of this study is that, although all of the desorption features that were observed are in the temperature range typically observed for bulk Pt metals, the desorption behavior cannot be related to that observed on any simple single-crystal surfaces.

• OSTI ID: 7167336
• Journal Information: Journal of Physical Chemistry; (USA), Vol. 93:5; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
NITRIC OXIDE
DESORPTION
DISSOCIATION
PLATINUM
CATALYTIC EFFECTS
ALUMINIUM OXIDES
CATALYSIS
CATALYSTS
EXPERIMENTAL DATA
PARTICLES
TEMPERATURE DEPENDENCE
ALUMINIUM COMPOUNDS
CHALCOGENIDES
DATA
ELEMENTS
INFORMATION
METALS
NITROGEN COMPOUNDS
NITROGEN OXIDES
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
TRANSITION ELEMENTS
400201* - Chemical &amp; Physicochemical Properties