INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
·
2021
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IF 5.816
Xuancheng Wang,Xuezhang Xiao,Jiaguang Zheng,Zhouming Hang,Wenping Lin,Zhendong Yao,Meng Zhang,Lixin Chen
Magnesium borohydride , Mg(BH 4 ) 2 , is ball-milled with Ti nano-particles. Such catalyzed Mg(BH 4 ) 2 releases more hydrogen than pristine Mg(BH 4 ) 2 does during isothermal dehydrogenation at 270, 280, and 290 °C. The catalyzed Mg(BH 4 ) 2 also exhibits better dehydrogenation kinetics than the pristine Mg(BH 4 ) 2 . Based on kinetics model fitting, the activation energy ( E a ) of the catalyzed Mg(BH 4 ) 2 is calculated to be lower than pristine Mg(BH 4 ) 2 . During partial dehydrogenation , the catalyzed Mg(BH 4 ) 2 releases 4.23 wt % (wt%) H 2 for the second dehydrogenation at 270 °C, comparing to 4.05, and 3.75 wt% H 2 at 280, and 290 °C. The reversibility of 4.23 wt% capacity is also one of the highest for Mg(BH 4 ) 2 dehydrogenation under mild conditions such as 270 °C as reported. 4 cycles of Mg(BH 4 ) 2 dehydrogenation are conducted at 270 °C. The capacities degrade during 4 cycles and tend to be stable at about 3.0 wt% for the last two cycles. By analyzing the hydrogen de/absorption products of the catalyzed sample, Mg(BH 4 ) 2 is found to be regenerated after rehydrogenation according to Fourier Transform Infrared (FTIR) spectroscopy. Ti nano-particles can react with Mg(BH 4 ) 2 during ball-milling and de/rehydrogenation. The products include TiH 1.924 , TiB, and TiB 2 , which can improve the dehydrogenation properties of Mg(BH 4 ) 2 from a multiple aspect.
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DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2021
·
IF 13.273
Jiaguang Zheng,Xuancheng Wang,Xuezhang Xiao,Hao Cheng,Liuting Zhang,Lixin Chen
Two dual-cation transition metal fluorides K 2 TiF 6 and K 2 NbF 7 are introduced into Mg(BH 4 ) 2 by ball-milling to catalyze the dehydrogenation of Mg(BH 4 ) 2 . According to the DSC and TPD results, the onset dehydrogenation temperature of Mg(BH 4 ) 2 doped with K 2 TiF 6 and K 2 NbF 7 are remarkably reduced to 105.4 and 118.0 °C, respectively. Meanwhile, both the K 2 TiF 6 and K 2 NbF 7 catalyzed systems can release more than 6.4 wt% H 2 under 280 °C, showing an improvement in dehydrogenation kinetics. In addition, the reversible capacity of the Mg(BH 4 ) 2 –3%K 2 TiF 6 system is 2.7 wt% at 280 °C in 250 min, which is enhanced comparing to that of pristine Mg(BH 4 ) 2 . X-ray diffraction, Fourier-transformed infrared and 11 B nuclear magnetic resonance investigations reveal that the K 2 TiF 6 actually acts as a catalytic precursor to react with Mg(BH 4 ) 2 , forming active hydrides of KBH 4 and TiH 2 , which further serve as catalyzing agents to facilitate the re-generation of Mg(BH 4 ) 2 from intermediates under moderate conditions.
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DOI
高影响因子
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
·
2020
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IF 4.939
Jiaguang Zheng,Zhendong Yao,Xuezhang Xiao,Xuancheng Wang,Jiahuan He,Man Chen,Hao Cheng,Liuting Zhang,Lixin Chen
Novel porous hollow carbon nanospheres (HCNS) have been synthesized and utilized as scaffold for LiBH 4 –Mg(BH 4 ) 2 eutectic borohydride (LMBH). Large loading amounts of LMBH (33, 50 and 67 wt%) have been melt-infiltrated into HCNS, and the significantly improved dehydrogenation properties have been discovered. The LMBH@HCNS composites not only exhibit high actual dehydrogenation amounts and fast hydrogen desorption rates, but also an increased reversible hydrogen storage capacities after three cycles without obvious degradation. Further structural tests have revealed that the over-infiltrated LMBH covering the spherical surface of HCNS could also contribute to the improved hydrogen storage behaviors, due to a strong interfacial adhesion effect that avoid LMBH from aggregation during de/rehydrogenation cycles.
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DOI
高影响因子
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
·
2019
·
IF 4.084
Xuancheng Wang,Xuezhang Xiao,Jiaguang Zheng,Xu Huang,Man Chen,Lixin Chen
The solvent-free amorphous Mg(BH 4 ) 2 composite was in-situ synthesized by ball milling LiBH 4 and MgCl 2 . It is found that the onset dehydrogenation temperature of the as-synthesized composite is 126.9 °C, which is roughly 156 °C lower than that of pristine Mg(BH 4 ) 2 . The activation energy of the amorphous Mg(BH 4 ) 2 and pristine Mg(BH 4 ) 2 for the first dehydrogenation step was calculated as 120.01 kJ/mol and 487.99 kJ/mol, respectively. Hence the kinetics improvement is certified by the lower E a value of the dehydrogenation process. When adding NbF 5 into the composite, the catalyzed composite exhibits better hydrogen storage properties compared to pristine and amorphous Mg(BH 4 ) 2 . The catalyzed composite starts to release hydrogen at proximately 120 °C with a total capacity of 10.04 wt%. The reversibility of the catalyzed composite is also improved. The capacity of the catalyzed composite at the second cycle is 5.5 wt%. For the third and fourth cycles the catalyzed composite can still liberate 4 wt% H 2 . Besides, the onset hydrogen desorption temperature during four cycles are extremely lower than those of pristine and amorphous Mg(BH 4 ) 2 . The peaks of the intermediate MgB 12 H 12 is detected by FTIR as the regenerated hydrogenation product in the catalyzed composite. It can be speculated from the detailed analysis that there are mainly three reasons for the improved properties. Firstly, the additive NbF 5 is favorable to enhance the hydrogen storage properties by modifying the dehydrogenation path and producing MgF 2 and NbB 2 as new products. Secondly, the in-situ formation of amorphous Mg(BH 4 ) 2 is likely to improve the dehydrogenation properties of the samples due to its different reactivity comparing to crystal ones. Finally, LiCl can serve as buffer in the composite and thus improve the dehydrogenation properties.
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）