Hydrogen-oxygen reaction over the Pt(111) surface: transient titration of adsorbed oxygen with hydrogen

Journal Article · Wed Sep 01 04:00:00 EDT 1982 · J. Catal.; (United States)

DOI:https://doi.org/10.1016/0021-9517(82)90167-1· OSTI ID:6596895

Gland, J L; Fisher, G B; Kollin, E B

The kinetics of the hydrogen-oxygen reaction have been characterized on a Pt(111) surface over the 300 to 450/sup 0/K temperature range by titration of adsorbed atomic oxygen with hydrogen in the 1.3 x 10/sup -6/ to 1.3 x 10/sup -7/ Pa (10/sup 8/ to 10/sup -9/ Torr) pressure range. These experiments were performed in an apparatus equipped with Auger electron spectroscopy, low energy electron diffraction, and a multiplexed mass spectrometer used for titration and thermal desorption measurements. The hydrogen-oxygen reaction has been studied by monitoring the water formation rate as a function of time for various temperatures, hydrogen pressures, and initial adsorbed oxygen concentrations. Adsorbed atomic oxygen forms islands of ordered atomic oxygen with a (2 x 2) structure under the conditions used during these experiments. Hydrogen reacts rapidly with adsorbed atomic oxygen to form water above 300/sup 0/K. Typically reaction probabilities per incident hydrogen molecule were as high as 0.5 over the temperature range studied. Isotope exchange experiments indicate statistical amounts of HDO are formed during titration of adsorbed oxygen with H/sub 2/-D/sub 2/ mixtures. This isotope result coupled with low temperature spectroscopic studies: (1) suggests that water formation proceeds via sequential addition of hydrogen first to adsorbed atomic oxygen, then to adsorbed hydroxyl to form the product water. A simple reaction model is proposed based on the assumption that the island structure of the adsorbed atomic oxygen limits the availability of oxygen for reaction; this simple model rationalizes the qualitative features of the titration data obtained. The model suggests that the key parameters affecting the behavior of the water formation reaction are the size and shape of the oxygen islands and the availability of adsorbed atomic hydrogen in the reaction zone.

• Research Organization: General Motors Research Labs., Warren, MI
• OSTI ID: 6596895
• Journal Information: J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 77:1; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400202 -- Isotope Effects
Isotope Exchange
& Isotope Separation
ADSORPTION
CATALYTIC EFFECTS
CHEMICAL REACTIONS
DATA
DEUTERIUM
ELEMENTS
EXPERIMENTAL DATA
HYDROGEN
HYDROGEN ISOTOPES
INFORMATION
ISOTOPES
ISOTOPIC EXCHANGE
KINETICS
LIGHT NUCLEI
METALS
NONMETALS
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
OXYGEN
PLATINUM
PLATINUM METALS
REACTION KINETICS
SORPTION
STABLE ISOTOPES
TEMPERATURE EFFECTS
TRANSITION ELEMENTS