Methylbenzyl Naphthalene: Liquid Organic Hydrogen Carrier for Facile Hydrogen Storage and Release

A new homocyclic methylbenzyl naphthalene (MBN) compound has been developed as a novel liquid organic hydrogen carrier (LOHC) medium with a high gravimetric hydrogen storage capacity of 6.44 wt % and good dehydrogenation ability. According to the results of theoretical calculations of designed MBN, MBN media possesses one of the lowest dehydrogenation enthalpies (<56 kJ molH2–1) among homocyclic LOHC media. The Friedel–Craft alkylation reaction allows the formation of an MBN regioisomeric mixture, which minimizes the production cost for practical applications. This mixture exists as a liquid with a high boiling point (>623 K) at ambient temperature. The H2 storage efficiency of MBN was optimized to achieve a yield of greater than 99% using a new Ru-based catalyst. The reaction monitoring study suggests the stepwise hydrogenation reaction of aromatic rings, which allows the proposed hydrogenation mechanism. The extraction of H2 from hydrogen-rich H16–MBN was conducted via a dehydrogenation reaction (yield > 99%) using a Pt/CeO2 catalyst, which enabled fast H2 release. The faster and facile dehydrogenation of MBN compared to the other reported homocyclic LOHC media coincides with the theoretical calculation results.