Improvement of hydrogen storage properties in MgH2 catalysed by K2NbF7. (2nd August 2018)

• Record Type: Journal Article
• Authors: Yahya, M.S.; Sulaiman, N.N.; Mustafa, N.S.; Halim Yap, F.A.; Ismail, M.
• Is Part Of: International journal of hydrogen energy. Volume 43:Number 31(2018)
• Page Start: 14532
• Page End: 14540
• Publication Date: 2018-08-02
• Subjects: Hydrogen storage -- Magnesium hydride -- Catalytic effect -- Sorption properties; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2018.05.157
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: The catalytic effects of K2 NbF7 on the hydrogen storage properties of MgH2 have been studied for the first time. MgH2 + 5 wt% K2 NbF7 has reduced the onset dehydrogenation temperature to 255 °C, which is 75 °C lower than the as-milled MgH2 . For the rehydrogenation kinetic, at 150 °C, MgH2 + 5 wt% K2 NbF7 absorbs 4.7 wt% of hydrogen in 30 min whereas the as-milled MgH2 only absorbs 0.7 wt% of hydrogen under similar condition. For the dehydrogenation kinetic, at 320 °C, the MgH2 + 5 wt% K2 NbF7 is able to release 5.2 wt% of hydrogen in 5.6 min as compared to 0.3 wt% by the as-milled MgH2 under similar condition. Comparatively, the E a value of MgH2 + 5 wt% K2 NbF7 is 96.3 kJ/mol, which is 39 kJ/mol lower compared to the as-milled MgH2 . The MgF2, the KH and the Nb that are found after the heating process are believed to be the active species that have improved the system properties. It is concluded that the K2 NbF7 is a good catalyst to improve the hydrogen storage properties of MgH2 . Highlights: Hydrogen storage properties of K2 NbF7 -doped MgH2 were investigated. The onset dehydrogenation temperature of K2 NbF7 -doped MgH2 reduced to 255 °C. Sorption properties of MgH2 is also improved after adding with K2 NbF7 . The in - situ formation of the MgF2, KH and Nb species play a synergetic role.