A dual borohydride (Li and Na borohydride) catalyst/additive together with intermetallic FeTi for the optimization of the hydrogen sorption characteristics of Mg(NH)/2LiH.

The present study deals with the material tailoring of Mg(NH)-2LiH through dual borohydrides: the reactive LiBH and the non-reactive NaBH. Furthermore, a pulverizer, as well as a catalyst FeTi, has been added in order to facilitate hydrogen sorption. Addition of LiBH to LiNH in a 1 : 3 molar ratio leads to the formation of Li(BH)(NH) which also acts as a catalyst. However, the addition of NaBH doesn't lead to any compound formation but shows a catalytic effect. The onset dehydrogenation temperature of thermally treated Mg(NH)-2LiH/(Li(BH)(NH)-NaBH) is 142 °C as against 196 °C for the basic material Mg(NH)-2LiH. However, with the FeTi catalyzed Mg(NH)-2LiH/(Li(BH)(NH)-NaBH, it has been reduced to 120 °C. This is better than other similar amide/hydride composites where it is 149 °C (when the basic material is catalyzed with LiBH). The FeTi catalyzed Mg(NH)-2LiH/(Li(BH)(NH)-NaBH sample shows better de/re-hydrogenation kinetics as it desorbs 3.9 ± 0.04 wt% and absorbs nearly 4.1 ± 0.04 wt% both within 30 min at 170 °C (with the H pressure being 0.1 MPa for desorption and 7 MPa for absorption). The eventual hydrogen storage capacity of Mg(NH)-2LiH/(Li(BH)(NH)-NaBH together with FeTi has been found to be ∼5.0 wt%. To make the effect of catalysts intelligible, we have put forward in a schematic way the role of Li and Na borohydrides with FeTi for improving the hydrogen sorption properties of Mg(NH)-2LiH.