Journal
JOURNAL OF CATALYSIS
Volume 263, Issue 2, Pages 220-227Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.jcat.2009.02.006
Keywords
SOFC; DFT; Steam reforming kinetics; Carbon deactivation; Ni alloys; Isotopic labeling
Categories
Funding
- US Department of Energy DOE-BES
- Division of Chemical Sciences [FG-0205ER15686]
- NSF [CBET 0756255]
- ONR [N00014-08-1-0122]
- DOENETL [FC26-05-NT-42516]
- National Automotive Center (NAC)
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We report the results of detailed kinetic studies for methane steam reforming on supported Ni and Sn/Ni surface alloy catalysts. The kinetic data were interpreted in terms of mechanism-based overall rate expression. We show that the activation of C-H bonds in methane is the rate-controlling step on both catalysts. Isotopic CH4/CD4 labeling studies were performed to independently verify the proposed mechanism. The role of Sri is to displace Ni atoms from under-coordinated sites on Ni particles and to move the critical reaction channels to more abundant well-coordinated sites. We show that previously observed increased resistance to carbon deactivation of Sn/Ni compared to monometallic Ni in hydrocarbon reforming reactions can be attributed to the Sn-induced lowering in the binding energy of carbon on low-coordinate sites, which serve as carbon nucleation centers, and to an enhanced propensity of Sn/Ni to oxidize carbon surface species. The conclusions derived from the experimental studies are in agreement with DFT calculations. (C) 2009 Elsevier Inc. All rights reserved.
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