Self-Catalyzing Hydrogen-Storage Material Yang, Jun; Sudik, Andrea; Siegel, Donald J ...
Angewandte Chemie (International ed.),
01/2008, Letnik:
47, Številka:
5
Journal Article
Recenzirano
Greater than the sum of its parts: Hydrogen storage in complex hydrides is accelerated by using the ternary composite 2 LiNH2/LiBH4/MgH2, which exhibits a “self‐catalyzing” reaction pathway that ...results in faster H2 desorption, lower desorption temperatures, and suppression of NH3 release in comparison to the constituent binary composites (see diagram). The enhanced properties arise from the incorporation of an ionic liquid phase (Li4BH3H10) and from ancillary‐reaction seeding of a reversible H2 storage reaction.
We recently reported (Yang, J.; et al. Angew. Chem., Int. Ed. 2008, 47, 882) a novel hydrogen storage composite involving a 2:1:1 LiNH2:LiBH4:MgH2 ratio. On the basis of in-depth experimental and ...computational analysis, this composite was found to release hydrogen via a complex multistep reaction cascade, which seeded the products of a subsequent reversible hydrogen storage reaction. This so-called autocatalytic reaction sequence was found to result in favorable kinetics, ammonia attenuation, and partial low-temperature reversibility. Here, we extend our original study by examining the effects of reactant stoichiometry on the ensuing hydrogen storage desorption pathway and properties. In particular, we examine four (LiNH2) X −(LiBH4) Y −(MgH2) Z composites, where X:Y:Z = 2:1:2, 1:1:1, 2:0.5:1, and 2:1:1 (original stoichiometry). For each sample, we characterize the postmilled mixtures using powder X-ray diffraction (PXRD) and infrared spectroscopy (IR) analyses and observe differences in the relative extent of two spontaneous milling-induced reactions. Variable-temperature hydrogen desorption data subsequently reveal that all composites exhibit a hydrogen release event at rather low temperature, liberating between 2.3 (1:1:1) and 3.6 (2:0.5:1) wt % by 200 °C. At higher temperatures (200−370 °C), the hydrogen release profiles differ considerably between composites and release a total of 5.7 (1:1:1) to 8.6 (2:0.5:1) wt %. Utilizing variable-temperature IR and PXRD data coupled with first-principles calculations, we propose a reaction pathway that is consistent with the observed phase progression and hydrogen desorption properties. From these data, we conclude that premilled reactant stoichiometry has a profound impact on reaction kinetics and high-temperature reaction evolution because of reactant availability. From this enhanced understanding of the desorption process, we recommend and test a stoichiometrically optimal ratio (3:1:1.5) which releases a total of 9.1 wt % hydrogen. Finally, we assess the reversibility (at 180 °C) of the four primary composites over two desorption cycles and find that only the 2:1:1 and 2:0.5:1 are reversible (3.5 wt % for 2:0.5:1).
We have investigated the ternary mixture of complex hydrides with stoichiometry 2LiNH2+LiBH4+MgH2, and have identified a set of novel hydrogen storage reactions. One of these reactions involves the ...known reversible reaction Mg(NH2)2+2LiH{left-right arrow}Li2Mg(NH)2+2H2. Previous studies have shown that initiating this reaction from the binary mixture 2LiNH2+MgH2 results in poor hydrogen desorption kinetics and a small amount of NH3 release. In contrast to this behavior, here we demonstrate that by starting from the ternary mixture 2LiNH2+LiBH4+MgH2, the above reaction can proceed at lower temperatures and with improved kinetics, while maintaining reversibility. The advantage of starting with the ternary mixture can be traced to the subsequent formation, melting, and reaction of Li4BH4(NH2)3 with MgH2 to form the mixed imide phase Li2Mg(NH)2, which acts as a seed for the reversible reaction, and is at least partly responsible for the improved kinetic response.
Mehr als die Summe der Teile: Das ternäre Komposit 2 LiNH2/LiBH4/MgH2 unterstützt einen „selbstkatalysierenden“ Reaktionspfad, der eine schnellere H2‐Desorption, niedrigere Desorptionstemperaturen ...und eine effektivere Unterdrückung der NH3‐Freisetzung als bei den binären Komponenten bewirkt (siehe Diagramm). Die verbesserten Eigenschaften werden auf die Entstehung einer ionischen Flüssigphase (Li4BH3H10) zurückgeführt, die die Bildung von Impfkeimen für eine zusätzliche reversible Wasserstoffspeicherreaktion vermittelt.
Retroviral gene transfer of the glucocerebrosidase gene to hematopoietic progenitor and stem cells has shown promising results in animal models and corrected the enzyme deficiency in cells from ...Gaucher patients in vitro. Therefore, a clinical protocol was initiated to explore the safety and feasibility of retroviral transduction of peripheral blood (PB) or bone marrow (BM) CD34+ cells with the G1Gc vector. This vector uses the viral LTR promoter to express the human glucocerebrosidase cDNA. Three adult patients have been entered with follow-up of 6-15 months. Target cells were G-CSF-mobilized and CD34-enriched PB cells or CD34-enriched steady state BM cells, and were transduced ex vivo for 72 hr. Patient 1 had PB cells transduced in the presence of autologous stromal marrow cells. Patient 2 had PB cells transduced in the presence of autologous stroma, IL-3, IL-6, and SCF. Patient 3 had BM cells transduced in the presence of autologous stroma, IL-3, IL-6, and SCF. At the end of transduction, the cells were collected and infused immediately without any preparative treatment of the patients. The transduction efficiency of the CD34+ cells at the end of transduction was approximately 1, 10, and 1 for patients 1, 2, and 3, respectively, as estimated by semiquantitative PCR on bulk samples and PCR analysis of individual hematopoietic colonies. Gene marking in vivo was demonstrated in patients 2 and 3. Patient 2 had vector-positive PB granulocytes and mononuclear bone marrow cells at 1 month postinfusion and positive PB mononuclear cells at 2 and 3 months postinfusion. Patient 3 had a positive BM sample at 1 month postinfusion but was negative thereafter. These results indicate that gene-marked cells can engraft and persist for at least 3 months postinfusion, even without myeloablation. However, the level of corrected cells (<0.02%) is too low to result in any clinical benefit, and glucocerebrosidase enzyme activity did not increase in any patient following infusion of transduced cells. Modifications of vector systems and transduction conditions, along with partial myeloablation to allow higher levels of engraftment, may be necessary to achieve beneficial levels of correction in patients with Gaucher disease.
We have investigated the ternary mixture of complex hydrides with stoichiometry 2LiNH
2
+
LiBH
4
+
MgH
2, and have identified a set of novel hydrogen storage reactions. One of these reactions ...involves the known reversible reaction Mg(NH
2)
2
+
2LiH
↔
Li
2Mg(NH)
2
+
2H
2. Previous studies have shown that initiating this reaction from the binary mixture 2LiNH
2
+
MgH
2 results in poor hydrogen desorption kinetics and a small amount of NH
3 release. In contrast to this behavior, here we demonstrate that by starting from the
ternary mixture 2LiNH
2
+
LiBH
4
+
MgH
2, the above reaction can proceed at lower temperatures
and with improved kinetics, while maintaining reversibility. The advantage of starting with the ternary mixture can be traced to the subsequent formation, melting, and reaction of Li
4BH
4(NH
2)
3 with MgH
2 to form the mixed imide phase Li
2Mg(NH)
2, which acts as a seed for the reversible reaction, and is at least partly responsible for the improved kinetic response.
