Zhongxuan Lin,Zhenluo Yuan,Huanhuan Zhang,Shuyan Guan,Xiaojiao Wang,Shiqian Zhao,Guangxin Fan,Yanping Fan,Baozhong Liu
Lowering the dehydrogenation temperature and maintaining high dehydrogenation capacity are greatly hindering the practical application of α-AlH 3 for the hydrogen fuel cell industry. Herein, the layered accordion-like V 2 C MXene is synthesized and doped into α-AlH 3 by mild ball milling . The 1 wt.% V 2 C-catalyzed α-AlH 3 possesses excellent dehydrogenation performance with a low initial decomposition temperature of 70.5 °C and a high hydrogen release capacity of 8.1 wt.%. Furthermore, 7.8 wt.% of hydrogen could be quickly released from α-AlH 3 -1 wt.% V 2 C composite within 15 min at 120 °C, with a lower activation energy of 69.5 kJ/mol than that of as-received sample. The excellent dehydrogenation performance is attributed to the high activity of the zero valence V catalyst which is transformed from the multivalent V during ball milling and to promote dissociation and reorganization of hydrogen. This effective approach significantly enhances the dehydrogenation of α-AlH 3 , providing a hopeful approach for modifying metal hydrides .
A comparative study was performed on four LiBH 4 -based hydrogen storage composites 2LiBH 4 + MgX 2 and 6LiBH 4 + CaX 2 (X = H and F). The composites with fluorides and those with corresponding hydrides exhibited similar hydrogen storage properties. The dehydrogenation of 2LiBH 4 + MgF 2 demonstrated a strong dependence on the hydrogen back pressure , similar to that of 2LiBH 4 + MgH 2 . The reversible hydrogen storage of 2LiBH 4 + MgF 2 was achieved under a back pressure of 5 bar at 450 °C. Dehydrogenation under lower H 2 pressures resulted in the production of Mg and thus a partial reversibility. In contrast, both 6LiBH 4 + CaH 2 and 6LiBH 4 + CaF 2 revealed reversible hydrogen storage properties regardless of the hydrogen back pressure. The structural difference between MgB 2 and CaB 6 may account for the observed differences in hydrogen storage properties of the Mg- and Ca-containing LiBH 4 reactive composites.
Jie Shao,Xuezhang Xiao,Lixin Chen,Xiulin Fan,Leyuan Han,Shouquan Li,Hongwei Ge,Qidong Wang
A system of 2LiH–MgB2 and its hydrogenated 2LiBH4–MgH2 is an attractive candidate for hydrogen storage. However, its hydriding–dehydriding kinetics have to be further improved for practical application. In the present work, three kinds of Ni–B nanoparticles with different crystalline states and particle sizes were prepared by wet-chemical reduction and mechanochemical methods, and then introduced into a 2LiH–MgB2 composite for catalytic enhancement. The catalytic roles of Ni–B nanoparticles on the hydriding–dehydriding properties were investigated systematically. The results show that all of the Ni–B nanoparticles can significantly enhance the hydriding–dehydriding kinetics of the 2LiH–MgB2 composite, resulting in no incubation period for the formation of MgB2 during dehydrogenation. The more disordered the amorphous structure and the smaller sized the Ni–B particles are, the better the catalytic effect that is obtained. Microstructure analyses clearly reveal the formation of the MgNi3B2 phase in the dehydriding process, which acts as the nucleation agent for MgB2 formation determined by an edge-to-edge model. Directly doping with Ni–B nanoparticles in the 2LiH–MgB2 system shows a higher hydrogen desorption capacity of 9.4 wt% and obtains a better catalytic efficiency than doping with NiCl2.
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