The dehydrogenation mechanism during the incubation period in nanocrystalline MgH2Electronic supplementary information (ESI) available. See DOI: 10.1039/c6cp07926a

• Main Authors: Shantilal Gangrade, Apurva, Aditya Varma, Akhil, Kishor Gor, Nikhil, Shriniwasan, Sweta, Tatiparti, Sankara Sarma V
• Format: Article
• Language: English
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c6cp07926a

The dehydrogenation mechanism during the incubation period in nanocrystalline MgH 2 (low α : converted metal fraction and d α /d t ) and the reasons for the occurrence of the incubation period at 320, 350, and 400 °C were investigated. Pre-existing Mg crystallites can enhance Mg nucleation during the incubation period, as suggested by the estimated activation energy for nucleation (12 ± 2 kJ per mol H). The released H-atoms enter MgH 2 as interstitials, as indicated by the MgH 2 unit-cell contraction, resulting in increased equatorial Mg-H bond length, decreased charge-density distribution in the interstitial region, as observed from the charge-density maps, and decreased H-H distance in the {001} plane up to the midway of the incubation period. Eventually, hydrogen vacancies are created, as indicated by the red shift in the E g and A 1g peaks of Raman spectra. The high estimated activation energy for the growth of Mg (209 ± 8 kJ per mol H) renders it difficult and explains the reason for the presence of an incubation period. The dehydrogenation mechanism during the incubation period in nanocrystalline MgH 2 (low α : converted metal fraction and d α /d t ) and the reasons for the occurrence of the incubation period at 320, 350, and 400 °C were investigated.