Remarkable hydrogen properties of MgH2 via combination of an in-situ formed amorphous carbon

Carbon-based materials have been proposed as an ideal medium to reduce the reaction energy barriers and improve the (de)hydrogenation kinetics of magnesium-based hydrogen storage material (MgH 2 ) in term of their excellent dispersion. However, tedious preparation process and uneven distribution of carbon restrict the application. Therefore, in this paper, we cover MgH 2 by in-situ formed amorphous carbon via a facile approach of co-sintering Mg with fluorene followed by hydriding combustion and ball milling processes, named as MgH 2 -carbonization product of fluorene (MgH 2 -CPF). As a result, the MgH 2 -CPF composite prepared at 823 K initially dehydrogenates at 557 K, 94 K lower than the as-milled MgH 2 (651 K). Meanwhile, the composite can release 5.67 wt% H 2 within 1000 s at 623 K. Even at a lower temperature of 423 K, the MgH 2 -CPF composite still reabsorbs 5.62 wt% H 2 within 3600 s, while the as-milled Mg can hardly absorb hydrogen under a same condition. Furthermore, by addition of CPF, the apparent activation energy of the system is decreased from 161.2 kJ/mol to 87.2 kJ/mol. Our finding suggests that the carbon layer can keep the MgH 2 from aggregation, promote hydrogen transport and improve the efficiency of hydrogen absorption and desorption. The dehydrogenation performance of MgH 2 has been significantly improved via covered an in-situ formed amorphous carbon from fluorene. • The MgH 2 covered by an in-situ formed amorphous carbon has been synthesized. • The in-situ formed amorphous carbon improves hydrogen storage performance of MgH 2 . • The MgH 2 -CPF composite can absorb 4.93 wt% H 2 within 60 s at 473 K. • The MgH 2 -CPF composite can release 5.67 wt% H 2 within 1000 s at 623 K.