Carbon dioxide activation and dissociation on ceria (110): A density functional theory study

Abstract

Ceria (CeO(2)) is a promising catalyst for the reduction of carbon dioxide (CO(2)) to liquid fuels and commodity chemicals, in part because of its high oxygen storage capacity, yet the fundamentals of CO(2) adsorption, activation, and reduction on ceria surfaces remain largely unknown. We use density functional theory, corrected for onsite Coulombic interactions (GGA+U), to explore various adsorption sites and configurations for CO(2) on stoichiometric and reduced ceria (110), the latter with either an in-plane oxygen vacancy or a split oxygen vacancy. We find that CO(2) adsorption on both reduced ceria (110) surfaces is thermodynamically favored over the corresponding adsorption on stoichiometric ceria (110), but the most stable adsorption configuration consists of CO(2) adsorbed parallel to the reduced ceria (110) surface at a split oxygen vacancy. Structural changes in the CO(2) molecule are also observed upon adsorption. At the split vacancy, the molecule bends out of plane to form a unidentate carbonate with the remaining oxygen anion at the surface; this is in stark contrast to the bridged carbonate observed for CO(2) adsorption at the in-plane vacancy. Also, we analyze the pathways for CO(2) conversion to CO on reduced ceria (110). The subtle difference in the energies of activation for the elementary steps suggest that CO(2) dissociation is favored on the split vacancy, while the reverse process of CO oxidation may favor the formation of the in-plane vacancy. We thus show how the structure and properties of the ceria catalyst govern the mechanism of CO(2) activation and reduction.

Catalytic activities of CeO2(110)–2 × 1 reconstructed surface

“…In this transition state (TS1), the distance of OC-O A was determined to be 1.700 Å and the O A atom was found to raise by~0.13 Å. Then, O A atom continued to raise by~0.40 Å to bind with CO and give rise to a bent CO 2 complex with O-C-O A angel of 139.2°as the intermediate state (IM1), which is similar to the calculated configuration of the CO 2 adsorbed species (136.9°) reported in the theoretical work by Cheng et al [55]. After its formation at top surface, the intermediate CO 2 may undergo direct desorption from the surface.…”

Comparative studies of porous carbon nanofibers by various activation methods

“…Over P/P 0 (0.1), the adsorbed volume was increased predominantly, which means that there are also mesopores on CNFs. quent activation at high temperature in CO 2 or H 2 O vapor [17][18][19][20]. The chemical activation method involves the carbonization of a raw material previously impregnated with a chemical agent.…”

Isothermal reverse water gas shift chemical looping on La0.75Sr0.25Co(1−)Fe O3 perovskite-type oxides

“…Amongst these various possibilities of carbon dioxide adsorption, the monodentate carbonate-type adsorption (Fig. 8a) is a prominent way of stable adsorption [51]. Comparing the different stable adsorption possibilities that can ultimately pave the way for carbon dioxide dissociation is a matter of further study.…”

“…In the model, one carbon dioxide molecule rested on the surface of the perovskite. Carbon dioxide can bind to the surface in a number of different ways in various sites [49][50][51]. Amongst these various possibilities of carbon dioxide adsorption, the monodentate carbonate-type adsorption (Fig.…”