The bonding, structure and reactions of CO2 adsorbed on clean and promoted metal surfaces

Abstract

The characteristics of the adsorption and reactions of CO2 on Rh, Pd, Pt, Ni, Fe, Cu, Re, Al, Mg and Ag metals are discussed with particular emphasis on the activation of the CO2 molecule. Strong spectroscopic evidence is presented for the formation of negatively charged COa-, which-depending on the nature of the metal-may dissociate into CO and 0, or transform into CO3 + CO. The presence of surface adatoms dramatically influences the adsorption and reactivity of COz. Alkali adatoms increase the binding energy of adsorbed COa, promote the dissociation and/or the transformation of CO2 into CO,+O. In the presence of preadsorbed oxygen the formation of carbonate of different structures predominates.

Supported Catalysts for CO2 Methanation: A Review

“…Transition metals were deeply investigated as active catalysts for CO2 hydrogenation [18][19][20], and affect the CO2 activation and reduction steps. Iron, cobalt, nickel, and copper show high catalytic properties for CO2 activation.…”

CO2 activation and dissociation on the low miller index surfaces of pure and Ni-coated iron metal: a DFT study

“…From the early 1980s onwards, several experimental studies have been undertaken to understand the behavior of CO2 on transition metal surfaces; these studies have been compiled in two reviews 9,10 . In general, except for a few late transition metals such as Fe, Ni, and Cu, CO2 was found not to be activated on clean transition metal surfaces, except when promoted by alkali metals.…”

Models for heterogeneous catalysts: studies at the atomic level

“…It should be noted, that thermal desorption studies on the system reveal that the formed oxalate may be desorbed as CO 2 upon heating the adsorbate to a temperature larger than 340 K. This is interesting, since there is also the possibility to form CO and carbonate (CO 3 2-) upon heating, an observation made for oxalates formed in the presence of alkali co-adsorbates (Freund and Roberts 1996;Solymosi 1991;Paul et al 1988;Toomes and King 1996). It seems, that the low oxophilicity of Au prevents the formation of carbonate thus rendering the formation and decomposition of oxalate reversible in this system.…”

“…This knowledge may now be used to proceed to a situation where molecules at the rim are actually involved in a chemical reaction. Here we combine the above discussed ability of the Au particles to accumulate negative charge and consider a reaction of carbondioxide (Freund and Roberts 1996;Solymosi 1991). To transfer an electron to an isolated CO 2 molecule affords 0.6 eV and is thermodynamically unfavorable (Compton et al 1975).…”