AVS 46th International Symposium
    Surface Science Division Wednesday Sessions
       Session SS-WeP

Paper SS-WeP3
Microkinetics of Formate Synthesis on Cu Catalysts

Wednesday, October 27, 1999, 5:30 pm, Room 4C

Session: Poster Session
Presenter: T. Fujitani, National Institute for Resources and Environment, Japan
Authors: T. Fujitani, National Institute for Resources and Environment, Japan
I. Nakamura, University of Tsukuba, Japan
H. Nishimura, University of Tsukuba, Japan
H. Nakano, University of Tsukuba, Japan
J. Nakamura, University of Tsukuba, Japan
Correspondent: Click to Email
The kinetics of formate synthesis by hydrogenation of CO@sub 2@ and formate decomposition has been studied on Cu(111) and Cu(110) surfaces using in-situ IRAS and STM apparatuses combined with a reactor (1 atm). It has been found that the formate synthesis does not depend on the surface structure of copper between Cu(111) and Cu(110). The activation energy of formate synthesis on Cu(111) and Cu(110) have been determined to be 68.3 and 69.7 kJ/mol, respectively. The microkinetics of the formate synthesis can be explained by that assuming an Eley-Rideal mechanism. On the other hand, the activation energy and the pre-exponential factor for formate decomposition on Cu(111) were different from those on Cu(110), indicating that the decomposition of formate species depend on the Cu surface structure. Furthermore, the decomposition rate of formate on Cu(111) is very different depending on the preparation method, the synthesis from CO@sub 2@ and H@sub 2@ at atmospheric pressure and the preparation by adsorption of HCOOH in UHV. However, the activation energy of the decomposition for both cases is close to each other, meaning that the frequency factor of the rate constant is different for the two cases. The difference can be explained by the different structures of formate observed by STM. In the presence of atomic hydrogen, the decomposition rate of the formate synthesized from CO@sub 2@ and H@sub 2@ increases and becomes equal to the decomposition rate of the formate prepared by the adsorption of HCOOH. The activation energies and the pre-exponential factors for both the formate synthesis and the formate decomposition on Cu/SiO@sub 2@ were in good agreement with those on Cu(111), suggesting that the surface structure of Cu for the Cu/SiO@sub 2@ catalyst is identical with the Cu(111) surface.