Hydrogen energy is considered to be a desired energy storage carrier because of its high-energy density, extensive sources, and is environmentally friendly. The development of hydrogen storage material, especially liquid organic hydrogen carrier (LOHC), has drawn intensive attention to address the problem of hydrogen utilization. Hydrogen carrier is a material that can reversibly absorb and release hydrogen using catalysts at elevated temperature, in which LOHC mainly relies on the covalent bonding of hydrogen during storage to facilitate long-distance transportation and treatment. In this review, the chemical properties and state-of-the-art of LOHCs were investigated and discussed. It reviews the latest research progress with regard to liquid organic hydrogen storage materials, namely N-ethylcarbazole, and the recent progress in the preparation of efficient catalysts for N-ethylcarbazole dehydrogenation by using metal multiphase catalysts supported by carbon–nitrogen materials is expounded. Several approaches have been considered to obtain efficient catalysts such as increasing the surface area of the support, optimizing particle size, and enhancing the porous structure of the support. This review provides a new direction for the research of hydrogen storage materials and considerations for follow-up research.

In this study, a series of amine-functionalized SBA-15-supported bimetallic Au–Pd nanoparticles (Au–Pd/SBA-15-Amine) as catalysts are successfully synthesized by surface functionalization and co-reduction and characterized by inductively coupled plasma-atomic emission spectroscopy, XRD, XPS, and TEM. The Au–Pd/SBA-15-Amine catalysts thus obtained are tested for the dehydrogenation of formic acid (FA)–sodium formate (SF). Among the tested Au–Pd/SBA-15-Amine catalysts, as-synthesized Au₂Pd₈/SBA-15-Amine exhibits 100% H₂ selectivity and outstanding catalytic activity with an initial turnover frequency (TOF) of 1786 h⁻¹ at 323 K; this superior catalytic activity is attributed to synergy between Au–Pd and SBA-15-Amine and the promotion effect of SF. At SF concentrations of greater than 0.5 mol L⁻¹, SF can partially participate in dehydrogenation. The facile synthesis of the Au–Pd/SBA-15-Amine catalyst is imperative for accelerating the widespread application of FA–SF mixtures as a promising hydrogen carrier.

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).

Bimetallic AgPd nanoparticles were successfully immobilized on graphitic carbon nitride (g-C₃N₄) functionalized SBA-15 for the first time by a facile co-reduction method.