title: Adsorption of CO2 and coadsorption of H and CO2 on potassium-promoted Cu(115).
abstract: The influence of potassium, in the submonolayer regime, on the adsorption and coadsorption of CO2 and H on a stepped copper surface, Cu(115), has been studied by photoelectron spectroscopy, temperature-programmed desorption, and work-function measurements. Based on the fast recording of C 1s and O 1s core-level spectra, the uptake of CO2 on K/Cu(115) surfaces at 120 K has been followed in real time, and the different reaction products have been identified. The K 2p3/2 peak exhibits a chemical shift of -0.4 eV with CO2 saturation, the C 1s peaks of the CO3 and the CO species show shifts of -0.8 and -0.5 eV, respectively, and the C 1s peak of the physisorbed CO2 exhibits no shift. The effects of gradually heating the CO2/K/Cu(115) surface include the desorption of physisorbed CO2 at 143 K; the desorption of CO at 193 K; the ordering of the CO3 species, and subsequently the dissociation of the carbonate with desorption at 520-700 K. Formate, HCOO-, was synthesized by the coadsorption of H and CO2 on the K/Cu(115) surface at 125 K. Formate formed exclusively for potassium coverages of less than 0.4 monolayer, whereas both formate and carbonate were formed at higher coverages. The desorption of formate-derived CO2 took place in the temperature range 410-425 K and carbonate-derived CO2 desorbed at 645-660 K, depending on the potassium coverage.
authors.affiliation: Institute of Physics, Aalborg University, 9220 Aalborg Øst, Denmark. jenson@physics.auc.dk
authors.forename: Jens
authors.initials: J
authors.lastname: Onsgaard
authors.forename: Søren V
authors.initials: SV
authors.lastname: Hoffmann
authors.forename: Palle
authors.initials: P
authors.lastname: Møller
authors.forename: P Jan
authors.initials: PJ
authors.lastname: Godowski
authors.forename: Jacob B
authors.initials: JB
authors.lastname: Wagner
authors.forename: Giorgio
authors.initials: G
authors.lastname: Paolucci
authors.forename: Alessandro
authors.initials: A
authors.lastname: Baraldi
authors.forename: Giovanni
authors.initials: G
authors.lastname: Comelli
authors.forename: Amela
authors.initials: A
authors.lastname: Groso