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Density functional study on the activation of methane over Pd 2 , PdO, and Pd 2 O clusters
Author(s) -
Broclawik Ewa,
Yamauchi Ryo,
Endou Akira,
Kubo Momoji,
Miyamoto Akira
Publication year - 1997
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/(sici)1097-461x(1997)61:4<673::aid-qua9>3.0.co;2-t
Subject(s) - chemistry , palladium , density functional theory , dimer , catalysis , activation energy , adsorption , oxidative addition , diatomic molecule , cluster (spacecraft) , methane , bond cleavage , hydrogen , moiety , computational chemistry , photochemistry , molecule , stereochemistry , organic chemistry , computer science , programming language
Simple functional models for elementary steps in the total oxidation of methane over supported palladium catalysts were investigated using density functional theory. Three simple cluster models were proposed, namely, the palladium dimer and PdO diatomic and linear Pd 2 O, to probe the mechanism of the methane activation on metallic and oxidized palladium phases, respectively. The strongest adsorption was found on Pd 2 , where also the C(SINGLE BOND)H bond became easily activated; however, no stable product of the C(SINGLE BOND)H bond scission was indicated. Similar hydrogen activation took place on Pd 2 O and, in addition, adsorbed methyl and OH species formed the most stable system after crossing a moderate energy barrier. The same product was previously found stable also in the case of PdO dimer but the activation barrier was high. On the Pd 2 O cluster, the process of energy barrier crossing was accomplished in two steps: easy formation of a free hydrogen moiety and actual oxidation, which made the overall process less demanding energetically. © 1997 John Wiley & Sons, Inc.