Synergistic catalysis of Ru single-atoms and zeolite boosts high-efficiency hydrogen storage

Abstract

Liquid organic hydrogen carriers (LOHCs) are promising hydrogen carriers that play an important role in the hydrogen economy. However, designing an efficient catalyst for realizing hydrogen storage with cost-effective and low-temperature is still a great challenge. Herein, we report a Ru single-atoms supported on *BEA zeolite catalyst (Ru(Na)/Beta), with the assistance of hydrogen spillover, which can remarkably enhance the hydrogenation of N-ethylcarbazole(NEC), N-propylcarbazole(NPC) and 2-methylindole (2-MID) at lower temperatures with lower Ru content (0.5 wt%). Notably, the obtained Ru(Na)/Beta catalyst exhibits excellent activity in the hydrogenation of NEC with the hydrogen uptake of 5.69 wt% and a conversion rate of > 99% within 1.5 h for the 6 MPa H2 at 100 °C, whereas the hydrogen uptake on traditional Ru/Al2O3 is only 2.97 wt% with the conversion rate of 67 % under the same conditions. It is found that highly dispersed Ru single-atoms boost hydrogen activation and the strong acid sites (Brønsted and Lewis) of zeolites promote the hydrogen spillover on the hydrogenation with N-heterocycles. Moreover, the synergistic effect of Ru single atoms and *BEA zeolite is crucial for accelerating the hydrogenation rate and lowering the activation energy (45.7 vs. 88.3 kJ/mol) compared with traditional Ru-based catalysts.