Effect of Magnesium Fluoride on Hydrogenation Properties of Magnesium Hydride

Abstract

Abstract:A cost effective catalyst is of great importance for consideration of MgH 2 as potential hydrogen storage material. In this regard, we investigated the catalytic role of alkaline metal fluoride on the hydrogen storage behavior of MgH 2 . Samples were synthesized by admixing 5 mol % MgF 2 into MgH 2 powder using planetary ball mill. Hydrogenation measurements made at 335˝C showed that in comparison to only 70% absorption by pure MgH 2 , catalyzed material absorbed 92% of theoretical capacity in less than 20 min and desorbed completely in almost the same time. Sorption studies done at lower temperatures revealed that complete absorption at temperature as low as 145˝C is possible. This is due to uniform distribution of MgF 2 nano particles within the MgH 2 powder. X-ray diffraction patterns also showed the presence of stable MgF 2 phase that does not decompose upon hydrogen absorption-desorption. Cyclic measurements done at 310˝C showed negligible loss in the overall storage capacity with cycling. These results reveal that the presence of the chemically inert and stable MgF 2 phase is responsible for good reversible characteristic and improved kinetics.

Simultaneous improvement of kinetics and thermodynamics based on SrF2 and SrF2@Gr additives on hydrogen sorption in MgH2

“…However, they have found significant decrease in achievable hydrogen storage capacity. Contrary to the studies of Santiago et al 17 , Jain et al 23 have found that when MgH 2 and MgF 2 are milled together, MgF 2 remains entact and doesn't dissociate and persists throughout the hydrogen sorption cycling. In these studies, MgH 2 -MgF 2 is shown to exhibit better hydrogen sorption than stand-alone MgH 2 .…”

Catalytic Tuning of Sorption Kinetics of Lightweight Hydrides: A Review of the Materials and Mechanism

“…This additional Mg-Ti-F species was found responsible for better catalytic activity of TiF 3 . Since in-situ formed MgF 2 has been suggested as one of the responsible component for catalytic enhancement, Jain et al [128] reported the effect of direct addition of MgF 2 and found that it is beneficial for kinetic enhancement as well as cyclic stability, with low sensitivity to atmospheric conditions and easy handling. Inspired by the merits of F ions, several researchers have developed different fluoride materials such as CeF 4 , NbF 5 , ZrF 4 , TiF 3 , TiF 4 etc.…”

Mechanical alloys Mg-Me (Me: Ti, Fe, Ni, Al) & Mg-Me1-Me2(Ме1:Al, Me2: Ti, Fe, Ni) with low resistance and improved kinetics of hydrogenation/dehydrogenation for hydrogen storage applications

“…These shortcomings authors try to solve by commercial MgH2 mechanical dispersion in the presence of various kinds of catalytic additives: transition 3d-, 4d-metals [1][2][3][4][5][6][7][8][9][10][11] and their oxides [12][13][14][15][16][17][18][19][20][21][22][23][24], fluorides [25], intermetallic compounds and additives of Al, Cu, Zn, In, Sn nontransition metals, graphite and others [26][27][28][29][30][31][32][33][34][35][36][37][38].…”