NMR study of diffusion of CO on alumina-supported Pt clusters

• Published in: Journal of physical chemistry (1952) Vol. 97; no. 46; pp. 12014 - 12019
• Main Authors: BECERRA, L. R, KLUG, C. A, SLICHTER, C. P, SINFELT, J. H
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 18.11.1993
• Subjects: 400102 > Chemical & Spectral Procedures; ACTIVATION ENERGY; CARBON COMPOUNDS; CARBON MONOXIDE; CARBON OXIDES; CHALCOGENIDES; Chemistry; DIFFUSION; ELEMENTS; ENERGY; Exact sciences and technology; General and physical chemistry; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; MAGNETIC RESONANCE; METALS; NUCLEAR MAGNETIC RESONANCE; OXIDES; OXYGEN COMPOUNDS; PLATINUM; PLATINUM METALS; RESONANCE; Solid-gas interface; Surface physical chemistry; SURFACE PROPERTIES; TRANSITION ELEMENTS 400201 > Chemical & Physicochemical Properties; Inorganic adsorbate; Binary compound; Particle size; Temperature; Atomic cluster; Activation parameter; Transition metal; NMR spectrometry; Surface diffusion; Experimental study; Gas solid adsorption; Medium effect; Platinum; Spectral line profile; Gas solid interface; Metallic adsorbent; Carbon monoxide; Kinetics; Platinoid; Activation energy
• ISSN: 0022-3654; 1541-5740
• DOI: 10.1021/j100148a029

The authors report an NMR study of carbon monoxide diffusion on surfaces of supported Pt clusters. They have implemented an NMR technique complementary to the other ones used in NMR to measure diffusion. They found that the rate of diffusion of CO on Pt depends on cluster size. For the large clusters (average diameter 100 A), the activation energy is about 6.5 [+-] 0.5 kcal/mol, in agreement with the value obtained by other methods for CO on Pt(111). For the small clusters (diameter about 12 A), the activation energy is about 10.5 [+-] 1 kcal/mol. The authors also found that CO is more mobile on a partially covered surface than on a saturated one. They found that, in the temperature range investigated, only about 50% of the molecules are moving. The authors explain the data by a model in which only bridge-bonded CO molecules are capable of moving, by jumping to other bridge sites, while CO molecules linearly bonded are immobile. 21 refs., 7 figs., 1 tab.