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Title: Methylene migration and coupling on a non-reducible metal oxide: The reaction of dichloromethane on stoichiometric α-Cr2O3(0001)

Abstract

The reaction of CH2Cl2 over the nearly-stoichiometric α-Cr2O3(0001) surface produces gas phase ethylene, methane and surface chlorine adatoms. The reaction is initiated by the decomposition of CH2Cl2 into surface methylene and chlorine. Photoemission indicates that surface cations are the preferred binding sites for both methylene and chlorine adatoms. Two reaction channels are observed for methylene coupling to ethylene in temperature-programmed desorption (TPD). A desorption-limited, low-temperature route is attributed to two methylenes bound at a single site. The majority of ethylene is produced by a reaction-limited process involving surface migration (diffusion) of methylene as the rate-limiting step. DFT calculations indicate the surface diffusion mechanism is mediated by surface oxygen anions. The source of hydrogen for methane formation is adsorbed background water. Chlorine adatoms produced by the dissociation of CH2Cl2 deactivate the surface by simple site-blocking of surface Cr3+ sites. Finally, a comparison of experiment and theory shows that DFT provides a better description of the surface chemistry of the carbene intermediate than DFT+U using reported parameters for a best representation of the bulk electronic properties of α-Cr2O3.

Authors:
 [1];  [1];  [2];  [2];  [1]
  1. Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States). Department of Chemical Engineering
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
OSTI Identifier:
1159417
Alternate Identifier(s):
OSTI ID: 1244764
Grant/Contract Number:  
FG02-97ER14751; AC05-00OR22725; AC02-98CH10886
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Surface Science
Additional Journal Information:
Journal Volume: 632; Journal ID: ISSN 0039-6028
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Temperature programmed desorption; XPS; Density functional calculations

Citation Formats

Dong, Yujung, Brooks, John D., Chen, Tsung-Liang, Mullins, David R., and Cox, David F. Methylene migration and coupling on a non-reducible metal oxide: The reaction of dichloromethane on stoichiometric α-Cr2O3(0001). United States: N. p., 2014. Web. doi:10.1016/j.susc.2014.09.008.
Dong, Yujung, Brooks, John D., Chen, Tsung-Liang, Mullins, David R., & Cox, David F. Methylene migration and coupling on a non-reducible metal oxide: The reaction of dichloromethane on stoichiometric α-Cr2O3(0001). United States. https://doi.org/10.1016/j.susc.2014.09.008
Dong, Yujung, Brooks, John D., Chen, Tsung-Liang, Mullins, David R., and Cox, David F. 2014. "Methylene migration and coupling on a non-reducible metal oxide: The reaction of dichloromethane on stoichiometric α-Cr2O3(0001)". United States. https://doi.org/10.1016/j.susc.2014.09.008. https://www.osti.gov/servlets/purl/1159417.
@article{osti_1159417,
title = {Methylene migration and coupling on a non-reducible metal oxide: The reaction of dichloromethane on stoichiometric α-Cr2O3(0001)},
author = {Dong, Yujung and Brooks, John D. and Chen, Tsung-Liang and Mullins, David R. and Cox, David F.},
abstractNote = {The reaction of CH2Cl2 over the nearly-stoichiometric α-Cr2O3(0001) surface produces gas phase ethylene, methane and surface chlorine adatoms. The reaction is initiated by the decomposition of CH2Cl2 into surface methylene and chlorine. Photoemission indicates that surface cations are the preferred binding sites for both methylene and chlorine adatoms. Two reaction channels are observed for methylene coupling to ethylene in temperature-programmed desorption (TPD). A desorption-limited, low-temperature route is attributed to two methylenes bound at a single site. The majority of ethylene is produced by a reaction-limited process involving surface migration (diffusion) of methylene as the rate-limiting step. DFT calculations indicate the surface diffusion mechanism is mediated by surface oxygen anions. The source of hydrogen for methane formation is adsorbed background water. Chlorine adatoms produced by the dissociation of CH2Cl2 deactivate the surface by simple site-blocking of surface Cr3+ sites. Finally, a comparison of experiment and theory shows that DFT provides a better description of the surface chemistry of the carbene intermediate than DFT+U using reported parameters for a best representation of the bulk electronic properties of α-Cr2O3.},
doi = {10.1016/j.susc.2014.09.008},
url = {https://www.osti.gov/biblio/1159417}, journal = {Surface Science},
issn = {0039-6028},
number = ,
volume = 632,
place = {United States},
year = {Wed Sep 17 00:00:00 EDT 2014},
month = {Wed Sep 17 00:00:00 EDT 2014}
}

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Cited by: 4 works
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