Theoretical and experimental study of reaction pathways for the interaction of CO{sub 2} with alkali-modified surfaces

Journal Article · Thu May 04 04:00:00 EDT 1995 · Journal of Physical Chemistry

DOI:https://doi.org/10.1021/j100018a040· OSTI ID:50475

Axelsson, O; Shao, Y; Paul, J ^[1]; Hoffmann, F M ^[2]

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1. KTH/Royal Inst. of Technology, Stockholm (Sweden)
2. EXXON Research and Engineering, Annandale, NJ (United States)

Previous work has shown that CO{sub 2} adsorption on bulk potassium leads to the formation of oxalate ions below room temperature. These C{sub 2}O{sub 4} groups decompose in vacuo to carbonates, CO{sub 3}, and CO around 300 K and the carbonates further to oxides and carbon dioxide above 700 K. The present work addresses reaction routes by calculations of adsorption coordinates in combination with spectroscopic data from time-resolved in situ infrared spectroscopy and analyses of desorbing species. Oxalate intermediates are formed by reactions between surface CO{sub 2} ions and adsorbed neutral molecules. Weakly adsorbed CO{sub 2} alone cannot follow this route. The energetics of oxalate formation is compared with CO{sub 2} adsorption on clean and oxidized potassium. Rearrangements between almost isoenergetic oxalates are discussed in connection with reaction routes and branching ratios. CO is released from one oxalate isomer, C{sub 2}O{sub 4}{sup 2-} - CO{sub 3}{sup 2-} + CO, with only a small activation barrier and bound as an entity in a K:CO complex at multilayer coverages. Desorption is only observed after annealing to around 650 K. Finally, CO and CO{sub 2} release as a result of carbonate decomposition and the reverse formation of CO{sub 3} are discussed, although these reactions are substrate dependent and not merely a rearrangement of an alkali compound. 40 refs., 9 figs.

• Sponsoring Organization: USDOE
• OSTI ID: 50475
• Journal Information: Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 18 Vol. 99; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
99 GENERAL AND MISCELLANEOUS
ADSORPTION
ALKALI METALS
BOND LENGTHS
CALCULATION METHODS
CARBON DIOXIDE
CHEMICAL REACTION KINETICS
DECOMPOSITION
HYDROGENATION
INFRARED SPECTRA
MOLECULAR ORBITAL METHOD
OXALATES
POTASSIUM
POTENTIALS
REACTION INTERMEDIATES
REDUCING AGENTS
SYNTHETIC FUELS