Palladium Supported on Carbon Nanotubes as a High-Performance Catalyst for the Dehydrogenation of Dodecahydro-N-ethylcarbazole

Abstract

Hydrogen storage in the form of liquid organic hydrides, especially N-ethylcarbazole, has been regarded as a promising technology for substituting traditional fossil fuels owing to its unique merits such as high volumetric, gravimetric hydrogen capacity and safe transportation. However, unsatisfactory dehydrogenation has impeded the widespread application of N-ethylcarbazole as ideal hydrogen storage materials in hydrogen energy. Therefore, designing catalysts with outstanding performance is of importance to address this problem. In the present work, for the first time, we have synthesized Pd nanoparticles immobilized on carbon nanotubes (Pd/CNTs) with different palladium loading through an alcohol reduction technique. A series of characterization technologies, such as X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectrometer (ICP-AES), X-ray photoelectron spectroscopy (XPS) and transmission electron spectroscopy (TEM) were adopted to systematically explore the structure, composition, surface properties and morphology of the catalysts. The results reveal that the Pd NPs with a mean diameter of 2.6 ± 0.6 nm could be dispersed uniformly on the surface of CNTs. Furthermore, Pd/CNTs with different Pd contents were applied in the hydrogen release of dodecahydro-N-ethylcarbazole. Among all of the catalysts tested, 3.0 wt% Pd/CNTs exhibited excellent catalytic performance with the conversion of 99.6% producing 5.8 wt% hydrogen at 533 K, low activation energy of 43.8 ± 0.2 kJ/mol and a high recycling stability (>96.4% conversion at 5th reuse).