Photoemission Study of CO<sub>2</sub>adsorbed on K/Cu(110). Analysis of Adsorbate Induced Structures

Godowski, P. J.; Onsgaard, J.; Hoffmann, S. V.; Nerlov, Jesper

doi:10.12693/aphyspola.95.423

Cited by 5 publications

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References 17 publications

(28 reference statements)

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“…During the adsorption of CO 2 on the interface, the carbonate-derived peaks grew in intensity much more than those of CO. Increasing the exposure to 1 L led to the appearance of new, additional features at 8.8 eV, 13.0 eV, and 14.7 eV that can be attributed to the linear CO 2 molecules, CO 2 (lin) (the 1p g , 1p u /3s u and 4s g orbitals, respectively). [33] Peak identifications, binding energies, and the assignments of the features in the photoemission valence band spectra are collected in Table 1. An increase in the K 3p intensity at 18.1 eV and a shift of the BE by À 0.3 eV were found, as is often observed in connection with the coadsorption of an alkali metal and simple molecular gases (O 2 , CO, CO 2 ).…”

Section: à2mentioning

confidence: 99%

Adsorption of CO₂ and Coadsorption of H and CO₂ on Potassium‐Promoted Cu(115)

et al. 2003

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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.

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Section: à2mentioning

confidence: 99%

Adsorption of CO₂ and Coadsorption of H and CO₂ on Potassium‐Promoted Cu(115)

et al. 2003

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“…While CO 2 interaction with clean metal surfaces leads to physisorption, a strong chemisorption interaction occurs when these promoting species are present, 3 and may, via follow-up reactions, give rise to carbonate or oxalate formation, thus reducing the CO 2 amount in air and, at the same time, obtaining a useful product. Several experimental studies of co-deposition of CO 2 and alkali metals on the (011) surface of various substrates have been reported involving CO 2 adsorption on K/Cu, [4][5][6][7][8] Cs/Cu, 9 K/Fe, 6,10,11 Cs/Fe, 11 Na/TiO 2 [12][13][14] and Cs/Ag. 15 Most of these previous works focus on methanol synthesis from activated CO 2 , but the molecular aspects of CO 2 activations are not fully understood.…”

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confidence: 99%

The interaction of CO2 with sodium-promoted W(011)

Viñes

Borodin

Höfft

et al. 2005

Phys. Chem. Chem. Phys.

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The activation of CO2 by interaction with Na atoms on tungsten was studied in a joint experimental/theoretical effort combining MIES, UPS (HeII) and first principles calculations. Experimentally, both the adsorption of Na on tungsten, followed by CO2 exposure to the Na-modified surface at 80 K, and the adsorption of CO2 on tungsten, followed by Na exposure to the CO2 covered substrate, were studied. Below about 120 K CO2 physisorbs on pure W(011), and the distance between the three main spectral features is as for gas phase CO2 (E(B) = 8.4, 12.1, 14.1 eV). When offered to a Na monolayer (ML) deposited onto W, CO2 is converted into a chemisorbed species. The spectral pattern is different from physisorbed CO2, and the three spectral features are shifted towards lower binding energies (E(B) = 6.3, 10.7, 13.9 eV). The chemisorption continues until all available Na species are converted into Na+ species. Additional CO2 offered to the system becomes physisorbed on top of the chemisorbed species. When a CO2 monolayer, physisorbed on tungsten at 80 K, is exposed to Na, the interaction leads initially to a decrease of the surface work function and to a rigid, global shift of all CO2 induced features towards larger binding energies by about 2 eV. Only beyond a minimum Na coverage of about 0.5 ML, chemisorbed species can be detected. We conclude that, initially, transfer of the Na(3s) electron to the tungsten substrate takes place. Above 0.5 ML Na coverage, back donation of charge to CO2 takes place whereby the physisorbed carbon dioxide species become converted into chemisorbed ones. The experimental results are interpreted with the help of first principle calculations carried out on suitable slab models. The structures and surface binding mode of the chemisorbed CO2 species are described. The calculated density of states for the most stable situations is in qualitative agreement with experimental data.

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