Structural characteristics and hydrogen storage properties of Sm2Co7

The structural characteristics and hydrogen-storage properties of the Ce2Ni7-type compound Sm2Co7 have been investigated for the first time. This alloy transforms to the β phase and then the γ phase upon hydrogenation. These two phases have been identified as Sm2Co7H2.9 and Sm2Co7H6.4, and their dehydrogenation enthalpies have been measured as 48.5 and 42.0 kJ/mol H2, respectively. Sm2Co7 shows excellent stability without obvious capacity loss after 50 cycles, and its hydrogenation process follows a three-dimensional-interface-controlled reaction at ambient temperature.