Prediction of Experimental Methanol Decomposition Rates on Platinum from First Principles |
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Authors: | Shampa Kandoi Jeff Greeley Marco A Sanchez-Castillo Steven T Evans Amit A Gokhale James A Dumesic Manos Mavrikakis |
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Affiliation: | (1) Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA |
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Abstract: | A microkinetic model for methanol decomposition on platinum is presented. The model incorporates competitive decomposition
pathways, beginning with both O–H and C–H bond scission in methanol, and uses results from density functional theory (DFT)
calculations Greeley and Mavrikakis, J. Am. Chem. Soc. 124 (2002) 7193, Greeley and Mavrikakis, J. Am. Chem. Soc. 126 (2004)
3910]. Results from reaction kinetics experiments show that the rate of H2 production increases with increasing temperature and methanol concentration in the feed and is only nominally affected by
the presence of CO or H2 with methanol. The model, based on the values of binding energies, pre-exponential factors and activation energy barriers
derived from first principles calculations, accurately predicts experimental reaction rates and orders. The model also gives
insight into the most favorable reaction pathway, the rate-limiting step, the apparent activation energy, coverages, and the
effects of pressure. It is found that the pathway beginning with the C–H bond scission (CH3OH→H2COH→HCOH→CO) is dominant compared with the path beginning with O–H bond scission. The cleavage of the first C–H bond in methanol
is the rate-controlling step. The surface is highly poisoned by CO, whereas COH appears to be a spectator species. |
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Keywords: | microkinetic density functional theory direct methanol fuel cells catalysis platinum methanol decomposition reaction kinetics hydrogen production methanol reforming |
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