AVS 47th International Symposium
    Surface Science Wednesday Sessions
       Session SS-WeP

Paper SS-WeP30
Formate Synthesis on Cu(111) by an Eley-Rideal Mechanism

Wednesday, October 4, 2000, 11:00 am, Room Exhibit Hall C & D

Session: Poster Session
Presenter: M. Sano, University of Tsukuba, Japan
Authors: M. Sano, University of Tsukuba, Japan
T. Fujitani, National Institute for Resources and Environment, Japan
J. Nakamura, University of Tsukuba, Japan
Correspondent: Click to Email
We have studied the kinetics and the mechanism of the formate synthesis by the hydrogenation of CO@sub 2@ over a Cu(111) model catalyst. The pressure dependence of H@sub 2@ and CO@sub 2@ upon the formation rate of the formate suggested that this reaction proceeds by an Eley-Rideal (E-R) mechanism. We thus examined the formate synthesis by the reaction of gaseous CO@sub 2@ and adsorbed hydrogen on Cu(111), where the experiments were carried out by an in-situ IRAS apparatus with a closed high pressure (1 atm) reactor. The Cu(111) sample was first exposed to 380 Torr H@sub 2@ to prepare a H/Cu(111) surface. Then, the formate synthesis was performed by exposing H/Cu(111) to CO@sub 2@ (380 Torr), where the sample temperature was constant at 308 K while the gas temperature was varied from 310 to 328 K. It was clearly shown that the bidentate formate species was formed on Cu(111) from the reaction of gaseous CO@sub 2@ and adsorbed hydrogen by IRA spectra. Moreover, the initial formation rate of the formate species increased with the heating temperature of gaseous CO@sub 2@ , indicating that the gaseous CO@sub 2@ temperature affects the formation rate of the formate synthesis. The activation energy and the pre-exponential factor of the rate constant were in good agreement with those of formate synthesis from CO@sub 2@ and H@sub 2@ at 760 Torr (P@sub CO2@ /P@sub H2@ = 1). The results mean that the formation rate of the formate synthesis only depends on CO@sub 2@ temperature, further indicating that the formate synthesis proceeds by the direct reaction between gaseous CO@sub 2@ and adsorbed hydrogen. We thus concluded that formate synthesis proceeds by an E-R mechanism.