Influence of K(2)NbF(7) Catalyst on the Desorption Behavior of LiAlH(4)

In this study, the modification of the desorption behavior of LiAlH(4) by the addition of K(2)NbF(7) was explored for the first time. The addition of K(2)NbF(7) causes a notable improvement in the desorption behavior of LiAlH(4). Upon the addition of 10 wt.% of K(2)NbF(7), the desorption temperature of LiAlH(4) was significantly lowered. The desorption temperature of the LiAlH(4) + 10 wt.% K(2)NbF(7) sample was lowered to 90°C (first-stage reaction) and 149°C (second-stage reaction). Enhancement of the desorption kinetics performance with the LiAlH(4) + 10 wt.% K(2)NbF(7) sample was substantiated, with the composite sample being able to desorb hydrogen 30 times faster than did pure LiAlH(4). Furthermore, with the presence of 10 wt.% K(2)NbF(7), 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 LiAlH(4). After analysis of the X-ray diffraction result, it is believed that the in situ formation of NbF(4), LiF, and K or K-containing phases that appeared during the heating process promoted the amelioration of the desorption behavior of LiAlH(4) with the addition of K(2)NbF(7).