Base-Metal Nanoparticle-Catalyzed Hydrogen Release from Ammine Yttrium and Lanthanum Borohydrides
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- 作者：Mehdi Mostajeran ; Eric Ye ; Serge Desgreniers ; R. Tom Baker
- 刊名：Chemistry of Materials
- 出版年：2017
- 出版时间：January 24, 2017
- 年：2017
- 卷：29
- 期：2
- 页码：742-751
- 全文大小：575K
- ISSN：1520-5002
文摘
Solid ammine metal borohydrides [M(BH4)m(NH3)n, AMBs] are promising materials for low temperature, high capacity hydrogen generation. Retention of metal halide co-products, arising from typical mechanochemical synthetic methods, is shown to have negative impacts on dehydrogenation properties of yttrium AMB. Halide-free yttrium and lanthanum AMBs, M(BH4)3(NH3)4, have been synthesized directly by treatment of MCl3 with 3 equiv of NaBH4 in thf followed by filtration, cooling, and exposure to liquid ammonia. The peak dehydrogenation temperature of the Y analog decreased from previously reported 179 to 160 °C while the ammonia peak temperature increased from 86 to 165 °C. To enhance the dehydrogenation properties and increase the selectivity of gas formation from these AMBs, base-metal nanoparticle catalysts, M′NPs; M′ = Fe, Co, Ni, and Cu) were employed. Preparation of the M′NPs from M′Cl2 and liquid hexylamine–borane allowed for separation of the B–Cl byproducts by subsequent solvent washing. Sonification of the M′NPs in toluene followed by addition of the solid AMB afforded composite AMB–M′NP–BN solids. Thermolysis data indicated a threefold reduction in ammonia release from the Y–Co and fourfold for the La–Fe composite. The purity of the released hydrogen was estimated to be 97.9 mol % for Y–Co and 98.9 mol % for La–Fe.