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Identifying Active Functionalities on Few‐Layered Graphene Catalysts for Oxidative Dehydrogenation of Isobutane
Author(s) -
Dathar Gopi Krishna Phani,
Tsai YuTung,
Gierszal Kamil,
Xu Ye,
Liang Chengdu,
Rondi Adam J.,
Overbury Steven H.,
Schwartz Viviane
Publication year - 2014
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201301006
Subject(s) - dehydrogenation , isobutane , catalysis , graphene , chemistry , oxide , density functional theory , oxygen , adsorption , thermal stability , heterogeneous catalysis , chemical engineering , photochemistry , materials science , inorganic chemistry , nanotechnology , organic chemistry , computational chemistry , engineering
The general consensus in the studies of nanostructured carbon catalysts for oxidative dehydrogenation (ODH) of alkanes to olefins is that the oxygen functionalities generated during synthesis and reaction are responsible for the catalytic activity of these nanostructured carbons. Identification of the highly active oxygen functionalities would enable engineering of nanocarbons for ODH of alkanes. Few‐layered graphenes were used as model catalysts in experiments to synthesize reduced graphene oxide samples with varying oxygen concentrations, to characterize oxygen functionalities, and to measure the activation energies for ODH of isobutane. Periodic density functional theory calculations were performed on graphene nanoribbon models with a variety of oxygen functionalities at the edges to calculate their thermal stability and to model reaction mechanisms for ODH of isobutane. Comparing measured and calculated thermal stability and activation energies leads to the conclusion that dicarbonyls at the zigzag edges and quinones at armchair edges are appropriately balanced for high activity, relative to other model functionalities considered herein. In the ODH of isobutane, both dehydrogenation and regeneration of catalytic sites are relevant at the dicarbonyls, whereas regeneration is facile compared with dehydrogenation at quinones. The catalytic mechanism involves weakly adsorbed isobutane reducing functional oxygen and leaving as isobutene, and O 2 in the feed, weakly adsorbed on the hydrogenated functionality, reacting with that hydrogen and regenerating the catalytic sites.