Mixture of methylbiphenyls as potential liquid organic hydrogen carriers

It has been challenging to find liquid organic hydrogen carriers (LOHCs) that satisfy both technological and environmental standards. In this study, we performed a comprehensive database and experimental search for the best candidate material and suggested a mixture of <i>m</i>-methylbiphenyls (<i>m</i>MBPs; <i>m</i> = 2, 3, or 4) as a promising LOHC. The mixture of mMBPs has a hydrogen storage capacity of 6.7 wt% H₂ with a melting point lower than -20 °C. A simple and efficient method of synthesis is also suggested. The LOHC can be readily hydrogenated <i>via</i> a Ru/Al₂O₃ catalyst. A complete dehydrogenation reaction can occur at a low temperature of 250 °C when the palladium catalyst is used. Through a molecular simulation study, we examined the effect of the methyl group of <i>m</i>MPB. We found that 2MBP is more favorable than the other forms for the dehydrogenation reaction. The combined theoretical and experimental results revealed that the suggested mixture of <i>m</i>MPB with the proposed composition is a promising LOHC.