Dehydrogenation of Dodecahydro‐N‐ethylcarbazole on Pt(111)

Abstract

Sloshing hydrogen: Liquid organic hydrogen carriers are high-boiling organic molecules, which can be reversibly hydrogenated and dehydrogenated in catalytic processes and are, therefore, a promising chemical hydrogen storage material. One of the promising candidates is the pair N-ethylcarbazole/perhydro-N-ethylcarbazole (NEC/H₁₂-NEC). The dehydrogenation and possible side reactions on a Pt(111) surface are evaluated in unprecedented detail.

Hydrogenation and dehydrogenation of nitrogen-doped graphene investigated by X-ray photoelectron spectroscopy

“…On average in all experiments a binding energy difference of 1.2 ± 0.1 eV is observed between the hydrogenated and unhydrogenated nitrogen species. The magnitude of this difference and its direction towards higher binding energy are in line with differences observed for other systems with hydrogenated and dehydrogenated (substituted/unsubstituted) nitrogen species, e.g., pyrrole [35], dodecahydro-N-ethylcarbazole on Pt(111) [36] and metalloporphyrins on Ag(111) [37]. The smaller value for this binding energy difference in our case might be due to different substrate or due to the very confined conjugated π-system in the case of pyrrole.…”

Alkyl chain length-dependent surface reaction of dodecahydro-N-alkylcarbazoles on Pt model catalysts

“…In the N 1s region, one Doniach-Sunjic was used (see, for example, the supplementary material of Ref. 10).…”

“…From these observations, we conclude that the behavior of H 12 -NPC and H 12 -NBC during adsorption is similar to the one of H 12 -NEC that was already addressed in great detail in our previous studies. [10][11][12][13]15 Next, we discuss the reactions occurring during heating of the adsorbed layers. To eliminate any contributions of the multilayer signal, which are difficult to separate from peaks of the chemisorbed species, for these experiments adsorption was performed at ∼250 K (except for the C 1s experiment for H 12 -NPC, where the molecule was adsorbed at 140 K and then heated to 250 K).…”

“…Concerning the dehydrogenation reaction, one specifically relevant aspect is the avoidance of unwanted side reactions during unloading, such as dealkylation of the N-alkyl substituent that would lead to an unfavorable change in the liquidus range of the LOHC system. In this context, we extensively studied H 12 -NEC regarding its dehydrogenation mechanism on various model catalysts including Pt(111), 10 Pd(111), 11 and on both Al 2 O 3 -supported Pt 12 and Pd 13 nanoparticles in ultrahigh vacuum (UHV) using high-resolution X-ray photoelectron spectroscopy (HR-XPS), infrared reflection-absorption spectroscopy (IRAS), and temperature-programmed molecular beam methods (TPMB). The N 1s spectrum of the nitrogen atom of NEC and H 12 -NEC is very suitable to monitor the C-N bond scission in HR-XPS.…”

“…On the single crystal surface, we obtain a detailed quantitative analysis of the reaction due to the highly defined nature of the substrate. 10,11,15 On the other hand, the investigation of supported model catalysts provides a more realistic picture of reactions taking place on the complex surface of an industrial heterogeneous catalyst. Note that for the hydrogenlean compounds, the abbreviations NEC, NPC, and NBC will be used (equivalent to H 0 -NEC, H 0 -NPC, H 0 -NBC, respectively).…”