The influences of Nb-containing oxides and ternary compound in hydrogen sorption performance were investigated. As faster desorption kinetic and lower activation energy were reported by addition of a ternary compound catalyst such as K 2 NiF 6 , the influence of KNbO 3 on hydrogen storage properties of MgH 2 has been investigated for the first time. The MgH 2 - KNbO 3 composite desorbed 3.9 wt% of hydrogen within 10 min, while MgH 2 and MgH 2 -Nb₂O₅ composites desorbed 0.66 wt% and 3.2 wt% respectively under similar condition. For MgH 2 with other Nb-contained catalysts such as Nb, NbO and Nb₂O 3 , the desorption rate was almost the same as the one registered for as-milled MgH 2 . The analysis of differential scanning calorimetry (DSC) showed that MgH 2 -KNbO 3 composite started to release hydrogen at ∼335 °C which is 50 °C lower compared to as-milled MgH 2 without any additives. The activation energy for the hydrogen desorption was estimated to be about 104 ± 6.8 kJ mol −1 for this material, while for the as-milled MgH 2 was about 165 ± 2.0 kJ mol −1 . It is believed that Nb-ternary oxide catalyst (KNbO 3 ) showed a good catalytic effect and enhance the sorption kinetics of MgH 2 .
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