Adsorption of atomic hydrogen on alumina by hydrogen spillover

Journal Article · Sat Jun 30 00:00:00 EDT 1979 · J. Catal.; (United States)

DOI:https://doi.org/10.1016/0021-9517(79)90266-5· OSTI ID:7141319

Kramer, R; Andre, M

Thermal desorption peaks were obtained of hydrogen adsorbed under various conditions on alumina, 1Vertical Bar3< platinum on alumina (A), 0.5Vertical Bar3< platinum on alumina (B), 1Vertical Bar3< nickel on alumina (C), and platinum foil. All samples desorbed hydrogen as a large or two unresolved peaks at approx. 130/sup 0/C attributed to dissociatively adsorbed H/sub 2/. Hydrogen adsorbed at 710 mm Hg and 400/sup 0/C on A or C desorbed at approx. 460/sup 0/C as well as at approx. 130/sup 0/C. Alumina in contact with atomic hydrogen generated in an electric discharge showed only the 460/sup 0/C desorption peak, which suggests that this peak is due to spillover hydrogen. Further experiments revealed that hydrogen spillover occurs by fast dissociative adsorption on platinum, fast spillover over the phase boundary, and rate-limiting diffusion on alumina. The saturation coverage of atomic hydrogen at 400/sup 0/C and 710 mm Hg was 1.44 trillion/sq cm on A and 2.2 trillion/sq cm on B, and the activation energy of diffusion was 28 kcal/mole on A and 29 kcal/mole on B; this indicates that the active site density is low compared with the number of possible surface hydroxyl groups, but that the sites hold the atomic hydrogen very strongly.

• Research Organization: University of Innsbruck
• OSTI ID: 7141319
• Journal Information: J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 58:2; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical &amp; Physicochemical Properties
ACTIVATION ENERGY
ADSORPTION
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CHALCOGENIDES
DESORPTION
ELEMENTS
ENERGY
HIGH TEMPERATURE
HYDROGEN
METALS
NICKEL
NONMETALS
OXIDES
OXYGEN COMPOUNDS
PLATINUM
PLATINUM METALS
SORPTION
SORPTIVE PROPERTIES
SURFACE PROPERTIES
TRANSITION ELEMENTS