In Situ Infrared Spectroscopy Analysis of Dehydrogenation of Perhydro‐ N ‐ethylcarbazole

ABSTRACT The dehydrogenation mechanism of perhydro‐ N ‐ethylcarbazole (12H‐NEC), a promising liquid organic hydrogen carrier (LOHC), on Pd/Al 2 O 3 catalyst was studied by in situ FT‐IR analysis. Spectra were collected in transmission mode using a 12H‐NEC/catalyst/KBr mixture pellet to overcome the difficulty of introducing low‐volatility 12H‐NEC. A peak‐deconvolution, assignment, and normalization protocol was developed to interpret the complex C─H stretching region from 3100 to 2750 cm −1 . The results indicate that dehydrogenation begins at the five‐membered ring and that species spectroscopically consistent with 8H‐NEC accumulate at approximately 100°C. A transient spectral state observed before this accumulation is consistent with an earlier partially dehydrogenated intermediate, for which 10H‐NEC is one possible structural assignment. This work provides experimental insight into the dehydrogenation mechanism of 12H‐NEC under mild conditions and may guide further efforts to improve the hydrogen‐storage performance of 12H‐NEC‐based LOHC systems.