Influence of K₂NbF₇ Catalyst on the Desorption Behavior of LiAlH₄

In this study, the modification of the desorption behavior of LiAlH₄ by the addition of K₂NbF₇ was explored for the first time. The addition of K₂NbF₇ causes a notable improvement in the desorption behavior of LiAlH₄. Upon the addition of 10 wt.% of K₂NbF₇, the desorption temperature of LiAlH₄ was significantly lowered. The desorption temperature of the LiAlH₄ + 10 wt.% K₂NbF₇ sample was lowered to 90°C (first-stage reaction) and 149°C (second-stage reaction). Enhancement of the desorption kinetics performance with the LiAlH₄ + 10 wt.% K₂NbF₇ sample was substantiated, with the composite sample being able to desorb hydrogen 30 times faster than did pure LiAlH₄. Furthermore, with the presence of 10 wt.% K₂NbF₇, the calculated activation energy values for the first two desorption stages were significantly reduced to 80 and 86 kJ/mol; 24 and 26 kJ/mol lower than the as-milled LiAlH₄. After analysis of the X-ray diffraction result, it is believed that the in situ formation of NbF₄, LiF, and K or K-containing phases that appeared during the heating process promoted the amelioration of the desorption behavior of LiAlH₄ with the addition of K₂NbF₇.