Contribution of metal-hydride species on the catalysts to catalytic performances

Metal-hydride (M-H) species typically exhibit high reactivities and distinctive chemical properties, which have prompted extensive investigations within the field of catalysis. Metal hydrides possess abundant M-H species within their structural composition, which can serve as extra hydrogen sources for chemical reactions in many cases. Additionally, they exhibit distinctive hydrogen absorption and desorption properties, making them a promising class of catalysts for hydrogenation and dehydrogenation reactions. In this Review, the mechanism and characterization of M-H species in catalytic reactions for M-H particles, molecular metal hydrides and hydride-doped metal nanoclusters were reviewed and compared. When metal oxides are used as catalysts, H2 can generally crack at the surface to produce highly M-H species to promote the reaction. Nevertheless, the intricate surface configuration of the catalyst and the transient nature of M-H intermediates have presented significant challenges in terms of detecting and characterizing them. A fundamental understanding of the reaction mechanisms and dynamic changes of M-H species could help design highly efficient catalysts for chemical reactions involving hydrogen.