Nonstoichiometric Yttrium Hydride-Promoted Reversible Hydrogen Storage in a Liquid Organic Hydrogen Carrier

N-Ethylcarbazole (NEC) is one of the most promising liquid organic hydrogen carriers (LOHCs), but its application is limited by sluggish kinetics due to lack of high-efficiency, low-cost catalysts. This work reports a cobalt (Co)-based catalyst promoted by nonstoichiometric yttrium hydride (YH3-x) to achieve high-efficiency, reversible hydrogen storage in NEC, with >5.5 wt % reversible hydrogen storage capacity could be achieved below 473 K, and with good kinetics. The YH3-x-promoted Co-based catalyst is the first non-noble metal catalyst with high activity for NEC hydrogenation and 12H-NEC dehydrogenation reactions. A mechanistic study suggests that YH3- x facilitates the reversible hydrogen transfer both in the hydrogenation and the dehydrogenation reactions. The nonstoichiometric YH3- x contained both lattice H and H vacancies with tunable H chemical potential serve as the H donor and H acceptor for reversible hydrogen transfer. Our results support the practical application of LOHCs and inspire new approaches for the utilization of conventional metal hydrides to promote versatile H transfer reactions.

Automated summary

A novel cobalt-based catalyst promoted by nonstoichiometric yttrium hydride was developed to achieve high-efficiency, reversible hydrogen storage in NEC, with good kinetics. This catalyst is the first non-noble metal catalyst with high activity for NEC hydrogenation and dehydrogenation reactions, suggesting new approaches for versatile hydrogen transfer reactions using conventional metal hydrides.