Open AccessModel Catalytic Studies of Liquid Organic Hydrogen Carriers: Dehydrogenation and Decomposition Mechanisms of Dodecahydro-N-ethylcarbazole on Pt(111)
Author(s) -
Max Amende,
Christoph Gleichweit,
Kristin Werner,
Stefan Schernich,
Wei Zhao,
Michael Lorenz,
Oliver Höfert,
Christian Papp,
M. Koch,
Peter Wasserscheid,
Mathias Laurin,
HansPeter Steinrück,
Jörg Libuda
Publication year - 2014
Publication title -
acs catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.898
H-Index - 198
ISSN - 2155-5435
DOI - 10.1021/cs400946x
Subject(s) - dehydrogenation , catalysis , photochemistry , desorption , adsorption , chemistry , decomposition , hydrogen storage , thermal desorption spectroscopy , x ray photoelectron spectroscopy , carbazole , hydrogen , materials science , organic chemistry , chemical engineering , engineering
Liquid organic hydrogen carriers (LOHC) are compounds that enable chemical energy storage through reversible hydrogenation. They are considered a promising technology to decouple energy production and consumption by combining high-energy densities with easy handling. A prominent LOHC is N -ethylcarbazole (NEC), which is reversibly hydrogenated to dodecahydro- N -ethylcarbazole (H 12 -NEC). We studied the reaction of H 12 -NEC on Pt(111) under ultrahigh vacuum (UHV) conditions by applying infrared reflection-absorption spectroscopy, synchrotron radiation-based high resolution X-ray photoelectron spectroscopy, and temperature-programmed molecular beam methods. We show that molecular adsorption of H 12 -NEC on Pt(111) occurs at temperatures between 173 and 223 K, followed by initial C-H bond activation in direct proximity to the N atom. As the first stable dehydrogenation product, we identify octahydro- N -ethylcarbazole (H 8 -NEC). Dehydrogenation to H 8 -NEC occurs slowly between 223 and 273 K and much faster above 273 K. Stepwise dehydrogenation to NEC proceeds while heating to 380 K. An undesired side reaction, C-N bond scission, was observed above 390 K. H 8 -NEC and H 8 -carbazole are the dominant products desorbing from the surface. Desorption occurs at higher temperatures than H 8 -NEC formation. We show that desorption and dehydrogenation activity are directly linked to the number of adsorption sites being blocked by reaction intermediates.