Mechanochemical assisted hydrogenation of Mg-CNTs-Ni:kinetics modeling and reaction mechanism

Abstract

MgH2, as one of the most potential hydrogen storage materials, has received considerable attention. However, its development has been plagued by its slow hydriding kinetics. Mechanochemical milling is an effective and convenient method for producing MgH2@CNTs-Ni through a solid–gas reaction between Mg-CNTs-Ni and H2. However, the hydriding kinetics and the corresponding mechanism during the milling have not been mentioned. Thus, hydriding kinetics of Mg-CNTs-Ni was researched for the purpose of gaining insights into the reaction mechanism and obtaining the best milling parameters. Also, phase transition during the milling was analyzed using XRD and TEM. It is apparent that the Avrami-Erofeev (AE) model can well describe the mechanochemical process, which contains solid solution, phase transition and growth-controlled regime. Besides, kinetics of hydrogenation is limited by nucleation and growth of MgH2. By fitting with the Arrhenius equation, average apparent activation energy for the hydrogenation of Mg-CNTs-Ni is estimated to be 47.8 kJ mol−1.