How Oxygen Vacancies Activate CO₂ Dissociation on TiO₂ Anatase (001)

Abstract

The adsorption, dissociation and diffusion of CO 2 on the anatase (001) surface was studied using DFT by means of the generalized gradient approximation using the Perdew-Burcke-Ernzerhof (PBE)-functional and applying corrections for long-range dispersion interactions. Different stable adsorption configurations were identified for the fully oxidized surface. The most stable adsorption configuration is the monodentated carbonate-like structure. Small energy barriers were identified for the conversion of a physisorbed to a chemisorbed configuration. CO 2 dissociation is found to be unfeasible on the stoichiometric surface. The introduction of oxygen vacancy defects gives rise to new highly stable adsorption configurations with a stronger activation of the C-O bonds. This leads to the possibility of exothermic dissociation of CO 2 with barriers up to 22.2 kcal/mol, corresponding to chemical lifetimes of less than 4 s at 300 K. These reactions cause a CO molecule to be formed, which will easily desorb, and the reduced surface to become oxidized. It is clear that oxygen vacancy defects play a key role in the catalytic activity of an anatase (001) surface. Oxygen vacancies play an important role in the dissociation of CO 2 on the anatase (001) surface, and will play a significant role in complex problems, such as the catalytic conversion of CO 2 to value-added chemicals.

Quantum-mechanical process of carbonate complex formation and large-scale anisotropy in the adsorption energy of CO2 on anatase TiO2Mishra1, Choudhary2, Roy3 et al. 2018Phys. Rev. Materials11190View full textAdd to dashboardCite

“…Concurrently, the C -O bond in CO 2 dilutes as their bond length increases from 1.18 to 1.28 Å. Finally, a carbonate complex is formed [32,35,46] which resembles an ideal carbonate anion where the O -C -O bond angle is 120° and the C -O bond length is 1.28 Å. Understanding the bonding mechanism will enable us to develop a phenomenology on adsorption as a function of both coverage and spatial distribution of the CO 2 molecule in a microscopic scale.…”

“…It suggests that CO 2 in this case is physisorbed where both surface 3 and adsorbate are negligibly deformed. On the other hand, the density functional theory (DFT) calculations for adsorption on (001) surface, using clusters [32,45] and slabs [35,46], yield stronger BE (-1.1 to -1.4 eV). In this case, the formation of a carbonate complex and the deformed surface suggests chemisorption of CO 2 molecule.…”

Defect engineering: A versatile tool for tuning the activation of key molecules in photocatalytic reactions

“…Thereby, the induced vacancies and CUS sites can efficaciously strengthen CO 2 chemisorption and deliver electrons for CO 2 activation [62][63][64][65] . Taking typical TiO 2 photocatalysts as an example, the adsorption and activation of CO 2 on defect sites have been comprehensively investigated by both theoretical simulations [66][67][68] and experimental techniques [69,70] . On anatase (001) surface, carbonate-like structure was identified as the most stable adsorption configuration of CO 2 molecule through density functional theory (DFT) calculations [71] .…”

“…On anatase (001) surface, carbonate-like structure was identified as the most stable adsorption configuration of CO 2 molecule through density functional theory (DFT) calculations [71] . Although CO 2 dissociation was infeasible on stoichiometric surface, the creation of OVs could give rise to new highly stable adsorption configurations with a stronger activation of C = O bond, causing the dissociation of C −O bond to form CO molecule [66] . The adsorption of CO 2 and dissociation of C = O bond at OVs on rutile (110) surface were experimentally investigated by scanning tunneling microscopy (STM) ( Fig.…”

Study on the Adsorption and Activation Behaviours of Carbon Dioxide over Copper Cluster (Cu4) and Alumina-Supported Copper Catalyst (Cu4/Al2O3) by means of Density Functional Theory

“…erefore, adsorption and activation of CO 2 have been extensively theoretically studied using the DFT method on many simple catalytic models such as flat transition metal surfaces [4][5][6][7][8][9] and oxide single crystals [10][11][12][13][14][15][16]. For example, in the work of Liu et al [6], adsorption and decomposition of CO 2 on the face (100) of four metals (Fe, Co, Ni, and Cu) in the 3d group element were investigated to understand the intrinsic chemical properties of the 3d elements.…”