Mechanochemical synthesis and effect of various additives on the hydrogen absorption–desorption behavior of Na3AlH6

Abstract

Sodium aluminum hydride has been extensively investigated for hydrogen storage applications whereas its intermediate decomposition compound Na 3 AlH 6 received much less attention, despite having a lower dissociation pressure and a reasonable hydrogen storage capacity of 3.0 wt%. In this work, Na 3 AlH 6 is synthesized through ball milling, starting from NaAlH 4 and 2 NaH in the presence of TiCl 3 catalyst precursor, and evaluated on its hydrogen sorption properties and cycle stability. Further addition of 8 mol% Al and 8 mol% activated carbon (AC) and their effect on both the hydrogen sorption properties and cycle stability have been investigated. In order to explore whether the introduction of the Al and AC additives would be more beneficial (in terms of hydrogen sorption behavior and cycle stability) after the Na 3 AlH 6 synthesis or during its synthesis, pre-synthesized Na 3 AlH 6-based measurements were also included in this work. TiCl 3-catalyzed NaAlH 4 ? 2 NaH sample showed a stable reversible hydrogen storage capacity of 1.7 wt%, which was further increased to 2.1 wt% with the addition of Al-powder and activated carbon AC.

Sustainable NaAlH4 production from recycled automotive Al alloy

“…The formation of Na 3 AlH 6 as an intermediate phase in the formation of NaAlH 4 was also previously mentioned in the literature. 24,47,54,55 Besides the previously mentioned phases, in the diffraction pattern of less pure NaAlH 4 , reflections of Si are also visible. of released hydrogen equal to 3.6 wt% is achieved.…”

Influence of Synthesis Gas Components on Hydrogen Storage Properties of Sodium Aluminum Hexahydride

“…The detailed description of the synthesis of TiCl 3 -doped Na 3 AlH 6 was reported in our previous publication [25]. NaH (60% dispersion in mineral oil, Sigma-Aldrich, St. Louis, MO, USA) and NaAlH 4 (95% technical grade, Sigma-Aldrich) both after purification, aluminum powder (99%, Sigma-Aldrich), activated carbon, and TiCl 3 (Sigma-Aldrich) were used.…”

“…The other reason for addition of aluminum is that the forming of Ti-Al alloy during doping processes would consume part of Al from Na 3 AlH 6 . To replace this consumed Al metal and as the result to maintain the reversibility of the system, the amount of 8 mol% Al is added [25].…”

Preface

“…Papers dealing with different aspects of mechanochemistry in organic systems are next, including a solvent-free process for the nitration of toluene [33], the synthesis of polymer blends [34], functionalizing protein materials with luminescent dyes and anticancer drugs [35] and synthesizing metal (Ce) phosphonates including products which can be only reached using ball milling [36]. Peinecke et al [37] and Romero and Huot [38] analyze the effect of high-energy milling in the hydrogen absorption-desorption properties of, respectively, a metal hydride Na 3 AlH 6 and a TiFe alloy, both doped with different additives. Finally, the last group of papers deals with the milling effect in the characteristics and properties of different materials with potential technological applications including antifungal calcium zinc hydroxide dihydrate [39], the sintering of commercial PZT powders [40] and the activation of natural zeolite powders [41] as well as for the recovery of Co and Li, from spent lithium ion batteries [42] and aluminum from natural pyrophyllite ore [43].…”