Dual-cation K2TaF7 catalyst improves high-capacity hydrogen storage behavior of MgH2

MgH 2 has been extensively regarded as a low-cost hydrogen storage material with high gravimetric hydrogen capacity of approximately 7.6 wt%. However, the hydrogen release and absorption kinetics in MgH 2 still needs further improving. For the first time, the catalytic impacts of a new dual-cation metal fluoride K 2 TaF 7 upon the hydrogen storage characteristics of MgH 2 have been investigated in this work. With only 1 wt% K 2 TaF 7 dopant , the initial dehydrogenation temperature of MgH 2 was lowered by about 130 °C, releasing more than 7.3 wt% hydrogen totally. The desorption activation energy of MgH 2 + 1 wt% K 2 TaF 7 composite was decreased to 107.2 ± 1.2 kJ mol −1 . Besides, at 190 °C, the dehydrogenated MgH 2 + 1 wt% K 2 TaF 7 sample could absorb 6.56 wt% H 2 , while pristine MgH 2 re-absorbed only 3.45 wt% H 2 . Further studies revealed that K 2 TaF 7 could react with MgH 2 during dehydrogenation and produce symbiotic hydrides KMgH 3 and TaH 0.8 , which could play the role of hydrogen pumps during hydrogen release and uptake. The cooperative catalysis between the hydrogen pump effect and the active interface in the multi-hydride area significantly enhanced the reversible hydrogen storage in the MgH 2 +1 wt% K 2 TaF 7 composite. This study provides new thinking for novel catalysts to elevate the hydrogen storage performance of MgH 2 .