Hydrogen spillover onto the rare-earth intermetallic compound SmMg3

Abstract

In the absorption of hydrogen by the rare-earth intermetallic compound SmMg₃ we have found that the process of hydrogen spillover is available as a means of improving its sorption properties. Active sites capable of activating hydrogen and then transferring to the adjoining intermetallic phase as hydrogen acceptors were formed when SmMg₃ was treated with various condensed-ring compounds (anthracene, phenanthrene, chrysene and perylene). These sites, in which the occurrence of charge-transfer to form electron donor–acceptor (EDA) complexes is established, seem to be effectively operative for hydrogen spillover. E.s.r. studies combined with hydrogen sorption measurements strongly suggest that the migrating hydrogen species are essentially monatomic in nature. To elucidate the characteristics of the migrating hydrogen the reaction of ethylene hydrogenation has been carried out. The present systems exhibited an accelerated formation of ethane in comparison with SmMg₃ alone. However, it is concluded that spilt-over hydrogen is only slightly responsible for the enhancement of catalytic activity.