Reactive Hydride Composite of Mg2NiH4 with Borohydrides Eutectic Mixtures

Abstract

Abstract:The development of materials showing hydrogen sorption reactions close to room temperature and ambient pressure will promote the use of hydrogen as energy carrier for mobile and stationary large-scale applications. In the present study, in order to reduce the thermodynamic stability of MgH 2 , Ni has been added to form Mg 2 NiH 4 , which has been mixed with various borohydrides to further tune hydrogen release reactions. De-hydrogenation/re-hydrogenation properties of Mg 2 NiH 4 -LiBH 4 -M(BH 4 ) x (M = Na, K, Mg, Ca) systems have been investigated. Mixtures of borohydrides have been selected to form eutectics, which provide a liquid phase at low temperatures, from 110 • C up to 216 • C. The presence of a liquid borohydride phase decreases the temperature of hydrogen release of Mg 2 NiH 4 but only slight differences have been detected by changing the borohydrides in the eutectic mixture.

Exploring Ternary and Quaternary Mixtures in the LiBH4‐NaBH4‐KBH4‐Mg(BH4)2‐Ca(BH4)2 System

“…For instance, the occurrence of a liquid phase enable easy tailoring of the decomposition temperature of borohydrides by both nanoconfinement, and in mixture with reactive hydride composites ,. The presence of a liquid phase in reactive hydride composites, provides a synergic effect in improving hydrogen release and cyclability ,. Improvements in hydrogen release properties in these systems are usually related to interfaces and microstructures, where the liquid phase promotes local contact between boundaries of the complex hydrides in the mixture .…”

A Review of the MSCA ITN ECOSTORE—Novel Complex Metal Hydrides for Efficient and Compact Storage of Renewable Energy as Hydrogen and Electricity

“…The latter species are boron donors to reversibly form the borohydride during the re-hydrogenation process. Dematteis et al [191] also observed a lower decomposition temperature of the RHC mixture if LiBH 4 is in a eutectic mixture with borohydrides that contain stable single charged metal cation, while a leftover of the more stable borohydrides was detected after cycling. In the eutectic mixture, the presence of double charged metal cation (i.e., Ca(BH 4 ) 2 and Mg(BH 4 ) 2 ) leads to a complete decomposition of the borohydrides.…”

“…It has been evidenced that composite systems containing lithium borohydride (LiBH 4 ) [190], or mixture of borohydrides, or borohydrides and reactive hydride composites, have improved hydrogen storage properties, especially when a liquid phase is involved [191]. Furthermore, variating composition and crystal structure can lead to a fine-tuning of kinetics and thermodynamics of hydrogen storage properties as a function of temperature, pressure and phase stability.…”

“…Dematteis et al [191] investigated the hydrogen storage properties of eutectic borohydrides mixed with Mg 2 NiH 4 to form reactive hydride composites (RHC). This approach evidenced enhanced kinetic and thermodynamics, and reversible hydrogen release under moderate pressure and temperature conditions [180].…”

Hydrogen Desorption in Mg(BH4)2-Ca(BH4)2 System

“…Mixtures of borohydrides may have an easier release of hydrogen than that of the individual constituents. In fact, the formation of solid solutions can lead to a lowering of the decomposition temperatures and a change of reaction mechanisms [19][20][21]. According to the Density Functional Theory (DFT) calculations of Ozolins et al [2], mixtures of Mg(BH 4 ) 2 and Ca(BH 4 ) 2 have better thermodynamic properties with respect to pure components.…”