Thermal Conversion of Unsolvated Mg(B3H8)2 to BH4– in the Presence of MgH2

Gigante, Angelina; Leick, Noémi; Lipton, Andrew S.; Tran, Ba L.; Strange, Nicholas A.; Bowden, Mark E.; Martinez, Madison B.; Moury, Romain; Gennett, Thomas; Hagemann, Hans‐Rudolf; Autrey, Tom

doi:10.1021/acsaem.1c00159

Cited by 18 publications

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“…Thermogravimetry (TG) experiments [59] revealed a 30 wt % mass loss setting in above ca 80 • C corresponding to the evolution of B 2 H 6 , B 5 H 9 and H 2 . The residual solid after heating to 200 • C was a mixture of mainly Mg(BH 4 ) 2 , Mg(B 10 H 10 ), and Mg(B 12 H 12 ), and the combined evolution of H 2 , B 2 H 6 , and B 5 H 9 was confirmed by mass spectrometry [60]. The addition of activated (ball-milled) MgH 2 to Mg(B 3 H 8 ) 2 results in a strong reduction in borane evolution and up to 88% conversion back to Mg(BH 4 ) 2 at 100 • C. The presence of activated MgH 2 thus substantially decreases the formation of (closo-hydro)borates and provides the necessary hydrogen for the conversion of B 3 H 8 − back into BH 4 − .…”

Section: Magnesium Borohydridementioning

confidence: 88%

Boron Hydrogen Compounds: Hydrogen Storage and Battery Applications

Hagemann

2021

Molecules

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About 25 years ago, Bogdanovic and Schwickardi (B. Bogdanovic, M. Schwickardi: J. Alloys Compd. 1–9, 253 (1997) discovered the catalyzed release of hydrogen from NaAlH4. This discovery stimulated a vast research effort on light hydrides as hydrogen storage materials, in particular boron hydrogen compounds. Mg(BH4)2, with a hydrogen content of 14.9 wt %, has been extensively studied, and recent results shed new light on intermediate species formed during dehydrogenation. The chemistry of B3H8−, which is an important intermediate between BH4− and B12H122−, is presented in detail. The discovery of high ionic conductivity in the high-temperature phases of LiBH4 and Na2B12H12 opened a new research direction. The high chemical and electrochemical stability of closo-hydroborates has stimulated new research for their applications in batteries. Very recently, an all-solid-state 4 V Na battery prototype using a Na4(CB11H12)2(B12H12) solid electrolyte has been demonstrated. In this review, we present the current knowledge of possible reaction pathways involved in the successive hydrogen release reactions from BH4− to B12H122−, and a discussion of relevant necessary properties for high-ionic-conduction materials.

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Section: Magnesium Borohydridementioning

confidence: 88%

Boron Hydrogen Compounds: Hydrogen Storage and Battery Applications

Hagemann

2021

Molecules

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“…The dynamics and lack of three-dimensional crystallinity are likely reasons why B 3 H − 8 forms during dehydrogenation of Mg(BH 4 ) 2 , despite unfavourable thermodynamic predictions [222]. Similarly, another recent DFT study confirmed that the solid-state reactive environment provides a unique energy landscape that can stabilize formation of B 6) [224]. This is surprising given that the reverse reaction, formation of Mg(B 3 H 8 ) 2 , is observed during the decomposition of Mg(BH 4 ) 2 .…”

Section: Boratesmentioning

confidence: 99%

“…B 3 H − 8 has not been observed during KBH 4 dehydrogenation because the decomposition occurs at temperatures above which KB 3 H 8 is stable.The thermal decomposition of KB 3 H 8 and Mg(B 3 H 8 ) 2 shows some similarities, but their reaction with hydrogen and metal hydrides is noticeably different, as shown in figure6. Mg(B 3 H 8 ) 2 begins to lose H 2 at ≈100 • C[224], while for KB 3 H 8 it initiates at ≈150 • C-200 • C[220]. Both disproportionate into the corresponding borohydride and some combination of closo-borates B 10 H 10 2− and B 12 H 12 2− .…”

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confidence: 99%

Hydrogen storage in complex hydrides: past activities and new trends

et al. 2022

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Intense literature and research efforts have focussed on the exploration of complex hydrides for energy storage applications over the past decades. A focus was dedicated to the determination of their thermodynamic and hydrogen storage properties, due to their high gravimetric and volumetric hydrogen storage capacities, but their application has been limited because of harsh working conditions for reversible hydrogen release and uptake. The present review aims at appraising the recent advances on different complex hydride systems, coming from the proficient collaborative activities in the past years from the research groups led by the experts of the Task 40 “Energy Storage and Conversion Based on Hydrogen” of the Hydrogen Technology Collaboration Programme of the International Energy Agency. An overview of materials design, synthesis, tailoring and modelling approaches, hydrogen release and uptake mechanisms and thermodynamic aspects are reviewed to define new trends and suggest new possible applications for these highly tuneable materials.

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“…Notably, the weak features at 2130 and 2075 cm −1 not present in the pristine Mg(BH 4 ) 2 or H 3 BO 3 / Mg(BO 2 ) 2 are suggesting that the boranes with bridged hydrogen atoms in the structure are formed at this stage. These could be (B 2 H 7 ) − , (B 3 H 7 ) 2− [22], (B 3 H 8 ) − [22,35,36], (B 4 H 10 ) 2− [18], etc. These peaks are accompanied by the peaks at > 2300 cm −1 , which are characteristic for the stretching of terminal hydrogen atoms of such boron hydride anions and Mg-H-B stretching [37].…”

Section: Groupmentioning

confidence: 99%

X-ray and Synchrotron FTIR Studies of Partially Decomposed Magnesium Borohydride

et al. 2022

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Magnesium borohydride (Mg(BH4)2) is an attractive compound for solid-state hydrogen storage due to its lucratively high hydrogen densities and theoretically low operational temperature. Hydrogen release from Mg(BH4)2 occurs through several steps. The reaction intermediates formed at these steps have been extensively studied for a decade. In this work, we apply spectroscopic methods that have rarely been used in such studies to provide alternative insights into the nature of the reaction intermediates. The commercially obtained sample was decomposed in argon flow during thermogravimetric analysis combined with differential scanning calorimetry (TGA-DSC) to differentiate between the H2-desorption reaction steps. The reaction products were analyzed by powder X-ray diffraction (PXRD), near edge soft X-ray absorption spectroscopy at boron K-edge (NEXAFS), and synchrotron infrared (IR) spectroscopy in mid- and far-IR ranges (SR-FTIR). Up to 12 wt% of H2 desorption was observed in the gravimetric measurements. PXRD showed no crystalline decomposition products when heated at 260–280 °C, the formation of MgH2 above 300 °C, and Mg above 320 °C. The qualitative analysis of the NEXAFS data showed the presence of boron in lower oxidation states than in (BH4)−. The NEXAFS data also indicated the presence of amorphous boron at and above 340 °C. This study provides additional insights into the decomposition reaction of Mg(BH4)2.

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Thermal Conversion of Unsolvated Mg(B₃H₈)₂ to BH₄^– in the Presence of MgH₂

Cited by 18 publications

References 78 publications

Boron Hydrogen Compounds: Hydrogen Storage and Battery Applications

Boron Hydrogen Compounds: Hydrogen Storage and Battery Applications

Hydrogen storage in complex hydrides: past activities and new trends

X-ray and Synchrotron FTIR Studies of Partially Decomposed Magnesium Borohydride

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