Effect of different transition metal fluorides TMFx (TM=Nb, Co, Ti) on hydrogen storage properties of the 3NaBH4-GdF3 system

Three kinds of transition metal fluorides TMF x (TM = Nb, Co, Ti) were introduced into the 3NaBH 4 -GdF 3 hydrogen storage system via mechanical milling. Their effects on the hydrogen storage behaviors of 3NaBH 4 -GdF 3 were systematically investigated by means of DSC and volumetric methods. All TMF x exhibited promoting effect on hydrogen desorption properties of 3NaBH 4 -GdF 3 to different degrees, especially when NbF 5 or TiF 3 was added. For example, the hydrogen desorption peak temperature was decreased by 17 °C with doping 3 mol% of NbF 5 . Besides, TiF 3 improved also the hydrogen absorption capacity and reversibility of 3NaBH 4 -GdF 3 . Based on XRD analyses, the role of TMF x on the dehydrogenation and the promoting effect of TiF 3 on the reversibility of 3NaBH 4 -GdF 3 were clarified. This work helped to understand the combination effect of rare earth metal fluoride (GdF 3 ) and transition metal fluorides on the reversible hydrogen storage properties of NaBH 4 .