Dehydrogenation mechanism of liquid organic hydrogen carriers: Dodecahydro-N-ethylcarbazole on Pd(111)

Amende M, Schernich S, Sobota M, Nikiforidis I, Hieringer W, Assenbaum D, Gleichweit C, Drescher HJ, Papp C, Steinrück HP, Görling A, Wasserscheid P, Laurin M, Libuda J (2013)

Publication Type: Journal article, Original article

Publication year: 2013


Original Authors: Amende M., Schernich S., Sobota M., Nikiforidis I., Hieringer W., Assenbaum D., Gleichweit C., Drescher H.-J., Papp C., Steinrück H.-P., Görling A., Wasserscheid P., Laurin M., Libuda J.

Publisher: Wiley-VCH Verlag

Book Volume: 19

Pages Range: 10854-10865

Journal Issue: 33

DOI: 10.1002/chem.201301323


Dodecahydro-N-ethylcarbazole (H-NEC) has been proposed as a potential liquid organic hydrogen carrier (LOHC) for chemical energy storage, as it combines both favourable physicochemical and thermodynamic properties. The design of optimised dehydrogenation catalysts for LOHC technology requires a detailed understanding of the reaction pathways and the microkinetics. Here, we investigate the dehydrogenation mechanism of H-NEC on Pd(111) by using a surface-science approach under ultrahigh vacuum conditions. By combining infrared reflection-absorption spectroscopy, density functional theory calculations and X-ray photoelectron spectroscopy, surface intermediates and their stability are identified. We show that H-NEC adsorbs molecularly up to 173 K. Above this temperature (223 K), activation of C-H bonds is observed within the five-membered ring. Rapid dehydrogenation occurs to octahydro-N-ethylcarbazole (H-NEC), which is identified as a stable surface intermediate at 223 K. Above 273 K, further dehydrogenation of H -NEC proceeds within the six-membered rings. Starting from clean Pd(111), C-N bond scission, an undesired side reaction, is observed above 350 K. By complementing surface spectroscopy, we present a temperature-programmed molecular beam experiment, which permits direct observation of dehydrogenation products in the gas phase during continuous dosing of the LOHC. We identify H-NEC as the main product desorbing from Pd(111). The onset temperature for H-NEC desorption is 330 K, the maximum reaction rate is reached around 550 K. The fact that preferential desorption of H -NEC is observed even above the temperature threshold for H -NEC dehydrogenation on the clean surface is attributed to the presence of surface dehydrogenation and decomposition products during continuous reactant exposure. © 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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Amende, M., Schernich, S., Sobota, M., Nikiforidis, I., Hieringer, W., Assenbaum, D.,... Libuda, J. (2013). Dehydrogenation mechanism of liquid organic hydrogen carriers: Dodecahydro-N-ethylcarbazole on Pd(111). Chemistry - A European Journal, 19(33), 10854-10865.


Amende, Maximilian, et al. "Dehydrogenation mechanism of liquid organic hydrogen carriers: Dodecahydro-N-ethylcarbazole on Pd(111)." Chemistry - A European Journal 19.33 (2013): 10854-10865.

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