Density Functional Theory Study of Methanol Decomposition on the CeO2(110) Surface
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Southern Illinois Univ., Carbondale, IL (United States)
Methanol decomposition on the stoichiometric CeO2(110) surface has been investigated using density functional theory slab calculations. Three possible initial steps to decompose methanol by breaking one of three bonds (O-H, C-O and C-H) of methanol were examined. The relative order of thermodynamic stability for the three possible bond scission steps is: C-H > O-H > C-O. We further isolated transition state and determined activation energy for each bond-breaking mode using the nudged elastic method. The activation barrier for the most favorable dissociation mode, the O-H bond scission, is 0.3 eV on the (110) surface. An even lower activation barrier (< 0.1 eV) has been obtained on the CeO2(111) surface for the same bond-breaking mode. We aslo calculated the pre-exponential factors based on the harmonic approximation and obtained the overall rate constants at 300 and 500 K for all three initial decomposition steps. In contrast to the order of thermodynamic stability, the calculated bond breaking barriers indicated a different bond breaking order kinetically: O-H > C-O > C-H. Our results are consistent with the previous experimental observation that methoxy is the dominant surface species after a stoichiometric CeO2 surface was exposed to methanol. The experimentally observed methanol chemistry was determined by the kinetics of initial dissociation steps rather than the thermodynamic stability of product states. Surface coverage of methanol was found to affect the relative stability between molecular and dissociative adsorption modes. Dissociative adsorption modes are preferred thermodynamically for methanol coverage up to 0.5 ML but only molecular adsorption was stable at full monolayer coverage. This work was supported by a Laboratory Directed Research and Development (LDRD) project of the Pacific Northwest National Laboratory (PNNL). The computations were performed using the Molecular Science Computing Facility in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), which is a U.S. Department of Energy national scientific user facility located at PNNL in Richland, Washington. Computing time was made under a Computational Grand Challenge “Computational Catalysis”. Part of the computing time was also granted by the National Energy Research Scientific Computing Center (NERSC).
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 927971
- Report Number(s):
- PNNL-SA-58492; 20691; TRN: US200816%%963
- Journal Information:
- Journal of Physical Chemistry. C, Vol. 112, Issue 11; ISSN 1932-7447
- Publisher:
- American Chemical Society
- Country of Publication:
- United States
- Language:
- English
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