Dehydrogenation of Mg-Fe-Ni-H based hydrogen storage tank under different operating temperatures and hydrogen flow rates

Effects of setting temperatures (Tset = 310-350 degrees C) and hydrogen flow rates (H2-FR = 0.2-0.6 standard L/min, SLM) on kinetics and reaction mechanisms during dehydrogenation of Mg-Fe-Ni-H based tank are investigated. Mg2FeH6-Mg2NiH4 composite under 1:1 mol ratio (-60 g) is packed in a small hydrogen storage tank with a packing volume of -96 mL. The experiment with high operating temperature, resulting in the enhanced decomposition rate requires fast H2-FR to reach the best dehydrogenation kinetics. In the case of de/rehydrogenation mechanisms, dehydrogenation under fast H2-FR leads to individual decomposition and reversibility of Mg2FeH6 and Mg2NiH4. The experiment under slow H2-FR hinders the decomposition of Mg2FeH6 and favors the formation of Mg2Fe(1-x)NixH6 via the reaction between Mg2FeH6 and Mg2Ni during dehydrogenation. The reversibility of Mg2Fe(1-x)NixH6 is accomplished by hydrogenation of Mg2Ni + Fe + Mg, benefiting the utilization of unreacted Fe upon cycling.