Theoretical Study of Syngas Hydrogenation to Methanol on the Polar Zn-Terminated ZnO(0001) Surface

Methanol synthesis from syngas (CO/CO2/H2) hydrogenation on the perfect Zn-terminated polar ZnO(0001) surface has been investigated using periodic density functional theory calculations. Our results show that direct CO2 hydrogenation to methanol is unlikely because, in the presence of surface atomic...

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Bibliographic Details
Published in:Journal of physical chemistry. C 2012-08, Vol.116 (30), p.15952-15961
Main Authors: Zhao, Ya-Fan, Rousseau, Roger, Li, Jun, Mei, Donghai
Format: Article
Language:English
Subjects:
10 SYNTHETIC FUELS
CARBONATES
Condensed matter: electronic structure, electrical, magnetic, and optical properties
Electron states
Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures
Electronic transport phenomena in thin films and low-dimensional structures
Environmental Molecular Sciences Laboratory
Exact sciences and technology
FORMALDEHYDE
FORMATES
FUNCTIONALS
HYDROGENATION
METHANOL
Methods of electronic structure calculations
Physics
SYNTHESIS
WATER
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Summary:Methanol synthesis from syngas (CO/CO2/H2) hydrogenation on the perfect Zn-terminated polar ZnO(0001) surface has been investigated using periodic density functional theory calculations. Our results show that direct CO2 hydrogenation to methanol is unlikely because, in the presence of surface atomic H and O, the highly stable formate (HCOO) and carbonate (CO3) readily produced from CO2 with low barriers of 0.11 and 0.09 eV will eventually accumulate and block the active sites of the ZnO(0001) surface. In contrast, methanol synthesis from CO hydrogenation is thermodynamically and kinetically feasible on the perfect ZnO(0001) surface. CO can be consecutively hydrogenated into formyl (HCO), formaldehyde (H2CO), and methoxy (H3CO) intermediates, leading to the final formation of methanol (H3COH). The reaction route via hydroxymethyl (H2COH) intermediate, a previously proposed species on the defective O-terminated ZnO(0001̅) surface, is kinetically inhibited on the perfect ZnO(0001) surface. The rate-determining step in the consecutive CO hydrogenation route is the hydrogenation of H3CO to H3COH. We also find that this final hydrogenation step is pronouncedly facilitated in the presence of water by lowering the activation barrier from 1.02 to 0.55 eV.
ISSN:1932-7447
1932-7455
DOI:10.1021/jp211055s