Hydrogenation and electrochemical studies of LaeMgeNi alloys M. Balcerzak * , M. Nowak, M. Jurczyk Pozna n University of Technology, Institute of Materials Science and Engineering, Jana Pawla II No 24, 61-138 Poznan, Poland article info Article history: Received 22 February 2016 Received in revised form 2 April 2016 Accepted 25 May 2016 Available online xxx Keywords: Hydrogen storage NieMH x Mechanical alloying LaeMgeNi alloys abstract LaeMgeNi alloys are potential candidates for hydrogen storage materials. In this study, mechanical alloying with subsequent annealing under an argon atmosphere at 973 K for 0.5 h, were used to produce La 2-x Mg x Ni 7 alloys (x ¼ 0, 0.25, 0.5, 0.75, 1). Shaker type ball mill was used. An objective of the present study was to investigate an influence of amount of Mg in alloy on electrochemical, hydrogenation and dehydrogenation properties of LaeMg eNi materials. X-ray diffraction analyses revealed formation of material with multi-phase structure. Obtained materials were studied by a conventional Sievert's type device at 303 K. It was observed that electrochemical discharge capacity and gaseous hydrogen storage capacity of LaeMgeNi alloys increases with Mg content to reach maximum for La 1.5 Mg 0.5 Ni 7 alloy. Moreover, all of LaeMgeNi alloys were characterized by improved hydrogen sorption kinetics in comparison to LaeNi alloy. © 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Introduction Metal LaeMgeNi-type hydrides are attractive class of mate- rials for hydrogen storage, due to their advantages such as: low price, low weight, high volumetric hydrogen storage density, good reversibility and fast sorption/desorption ki- netics [1]. Among many studied metal hydrides, LaeNi-based alloys paid much attention in recent years as they are candidates for hydrogen storage materials and also for negative electrode materials of NieMH x secondary batteries. LaeNi binary sys- tem contains of seven intermetallic phases. The most studied was so far LaNi 5 phase [2]. However, due to the limited hydrogen storage capacity of LaNi 5 phase, La-richer com- pounds like La 2 Ni 7 have been investigated as they are characterized by larger H-uptake [2e4]. However, La 2 Ni 7 alloy is characterized by poor cycle stability. Up to now, several methods have been applied to improve hydrogen storage properties of LaeNi-based alloys [4]. One of them is chemical modification. In the past, in order to improve the electrochemical properties of LaeNi alloys, La or Ni element was partially substituted by other transition metals [4e8]. Partial substitution of La by Mg was used to stabilize a large reversible plateau pressure and to reduce the molar mass, which leads to improved weight capacities [2,8]. More- over, the price of Mg element is lower than of La. There are many methods of hydrogen storage materials production, but so far, most of the LaeNi-based materials were obtained by vacuum induction melting [3,4,6]. In the literature, there is no data on production of La 2 Ni 7 -based al- loys directly from mechanical alloying (MA) process. This * Corresponding author. Tel.: þ48 61 665 3779; fax: þ48 61 665 3576. E-mail address: mateusz.balcerzak@put.poznan.pl (M. Balcerzak). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy xxx (2016) 1 e8 http://dx.doi.org/10.1016/j.ijhydene.2016.05.220 0360-3199/© 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Please cite this article in press as: Balcerzak M, et al., Hydrogenation and electrochemical studies of LaeMgeNi alloys, International Journal of Hydrogen Energy (2016), http://dx.doi.org/10.1016/j.ijhydene.2016.05.220