Remarkably fast low-temperature hydrogen storage into aromatic benzyltoluenes over MgO-supported Ru nanoparticles with homolytic and heterolytic H2 adsorption

Abstract Hydrogen storage into aromatic compounds under mild conditions is a stringent issue in liquid organic hydrogen carrier (LOHC) systems. Herein, we report a highly active Ru/MgO catalyst in the hydrogenation of monobenzyltoluene and dibenzyltoluene at low temperatures. When MgO with basic surface oxygen was employed as a support, Ru/MgO showed a faster H2 storage rate and superior kinetic parameters than the other supported Ru catalysts. The better catalytic performance of Ru/MgO was explained by the results of characterization and control experiments. Ru/MgO could adsorb the large amounts of monobenzyltoluene and hydrogen with higher strength. Particularly, homolytic and heterolytic hydrogen adsorption modes were identified in Ru/MgO, unlike Ru/Al2O3 showing homolytic H2 adsorption. Density functional theory calculations confirmed heterolytic H2 dissociation near the Ru-MgO interface, which assured the hydrogenation efficiency of Ru/MgO. Consequently, Ru/MgO is highly recommended for fast hydrogen storage into aromatic LOHC compounds at low temperatures.