Enhancement of hydrogen-storage performance of MgH2 by Mg2Ni formation and hydride-forming Ti addition

• Published in: International journal of hydrogen energy 2012-12, Vol.37 (23), p.18133-18139
• Main Authors: Song, Myoung Youp, Kwak, Young Jun, Lee, Seong Ho, Song, Jiyoung, Mumm, Daniel R.
• Format: Article
• Language: English
• Subjects: Activated; Activation; Alternative fuels. Production and utilization; Applied sciences; Chemical reactions; Energy; Exact sciences and technology; Fuels; Hydrides; Hydrogen; Hydrogen storage; Inverse; Mg2Ni formation; Ni and Ti addition; Performance enhancement; Reactive mechanical grinding; Starting material MgH2; Titanium
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2012.09.041

MgH2, rather than Mg, was used as a starting material in this work. A sample with a composition of MgH2–10Ni–4Ti was prepared by reactive mechanical grinding. Activation of the sample was completed after the first hydriding cycle. At n = 1, the sample desorbed 2.53 wt% H for 10 min, 3.99 wt% H for 20 min, 4.58 wt% H for 30 min, and 4.68 wt% H for 60 min at 593 K under 1.0 bar H2. At n = 2, the sample absorbed 3.59 wt% H for 5 min, 4.55 wt% H for 25 min, and 4.60 wt% H for 45 min at 593 K under 12 bar H2. The inverse dependence of the hydriding rate on the temperature in the initial stage and the normal dependence of the hydriding rate on the temperature in the later stage were discussed. The rate-controlling step for the dehydriding reaction of activated MgH2–10Ni–4Ti was analyzed as the chemical reaction at the hydride/α-solid solution interface. Desorbed hydrogen quantity Hd versus time t curves at 593 K under 1.0 bar H2 for activated MgH2 (at 593 K), MgH2–15Ni after RMG (at 573 K), and MgH2–10Ni–4Ti (at 593 K). [Display omitted] ► Preparation of MgH2–10Ni–4Ti by reactive mechanical grinding. ► Completion of activation after the first hydriding cycle. ► At n = 1, desorption of hydrogen of 4.68 wt% at 593 K under 1.0 bar H2 for 60 min ► Inverse dependence of hydriding rate on temperature in the initial stage. ► Analysis of rate-controlling step for dehydriding reaction of MgH2–10Ni–4Ti.