Available online at www.sciencedirect.com ScienceDirect Materials Today: Proceedings 5 (2018) 23235–23241 www.materialstoday.com/proceedings 2214-7853 © 2018 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of the Conference Committee Members of International Conference on Advances in Energy Research 2015 (ICAER-2015). ICAER-2015 Hydrogen Sorption Mechanism of Magnesium (Hydride) Sweta Shriniwasan a,* , Nikhil Gor a , Sankara Sarma V Tatiparti a a Department of Energy Science and Engineering, Indian Institute of Technology Bombay, Mumbai-400076, India Abstract Hydrogenation mechanism of magnesium involves hydride nucleation and growth by interfacial movement followed by H-atom diffusion limited hydride growth. Using the Johnson-Mehl-Avrami-Kolmogrov (JMAK) equation, the transition from interfacial to diffusional growth is studied during hydrogenation at several temperatures. The growth dimensionality (n) decreases with time from n>0.50 to n<0.50. Constant interface velocity (U) suggests interfacial growth in the n>0.50 regime. Diffusional growth in the n<0.50 regime is supported by decreasing U, core-shell (Mg-MgH 2 ) structure and the estimated diffusion coefficient (D). Hydride growth transits from interfacial to diffusional growth at n ≈ 0.50. © 2018 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of the Conference Committee Members of International Conference on Advances in Energy Research 2015 (ICAER-2015). Keywords: MgH 2 ; hydrogen sorption; JMAK; interfacial growth; diffusional growth 1. Introduction Magnesium is a promising candidate for on-board hydrogen storage [1,2]. However, its practical use is limited by its slow kinetics of (de)hydrogenation [1,3]. Hydrogenation of Mg involves chemisorption, nucleation and growth of the hydride phase [4]. Hydride phase growth can occur by interface movement followed by diffusion limited growth [5]. However, these mechanisms of growth are not easily distinguishable due to variations in experimental conditions, particle size/shape irregularities, different catalyst additions etc. E.g. In a study, hydrogenation of Mg at 300 °C suggests that 3D diffusion is the governing mechanism [6]. In another study, dehydrogenation of MgH 2 -Ni exhibiting different morphologies were investigated using in-situ ultra-high voltage transmission electron * Corresponding author. Tel.: +91 22 2576 7672 E-mail: sweta_s@iitb.ac.in