Electrochemical hydriding performance of MgaTMaMm (TM=transition metals, Mm=mischmetal) alloys for hydrogen storage

• Published in: Transactions of Nonferrous Metals Society of China 2013-07, Vol.23 (7), p.2047-2059
• Main Authors: Knotek, V, VOJTACH, D
• Format: Article
• Language: English
• Subjects: Alloys; China; Diffraction; Glow discharges; Hydrides; Hydrogen storage; Spectrometry; Spectroscopy
• ISSN: 1003-6326
• DOI: 10.1016/S1003-6326(13)62695-3

Eighteen as-cast binary MgaNi, MgaMm and ternary MgaNiaMm and MgaNiaTM (TM=transition metals (Cu, Zn, Mn and Co); Mm = mischmetal containing Ce, La, Nd and Pr) alloys were hydrided by an electrochemical process to determine the alloys with the most potential for electrochemical hydrogen storage. The alloys were hydrided in a 6 mol/L KOH solution at 80 degree C for 480 min and at 100 A/m2. To assess the electrochemical hydriding performance of alloys, maximum hydrogen concentrations, hydrogen penetration depths and total mass of absorbed hydrogen in the alloys were measured by glow discharge spectrometry. In addition, the structures and phase compositions of the alloys both before and after hydriding were studied by optical and scanning electron microscopy, energy dispersive spectrometry and X-ray diffraction. It was determined that the highest total amount of hydrogen was absorbed by the Mga25Nia12Mm and Mga26Ni (mass fraction, %) alloys. The maximum hydrogen concentrations in the Mga25Nia12Mm and Mga26Ni alloys were 1.0% and 1.6%, respectively. The main hydriding product was the binary MgH2 hydride, and the ternary Mg2NiH4 hydride was also detected in the Mga25Nia12Mm alloy. The electrochemical hydriding parameters achieved are discussed in relation to the structures of alloys, alloying elements and hydriding mechanisms.