Ce基催化剂对2LiBH_4/MgH_2放氢性能的影响

Effects of Ce-Based Catalysts on Hydrogen Storage Properties of 2LiBH_4/MgH_2 Composite

采用球磨方法制备了2LiBH4/MgH2复合储氢材料体系,用XRD、FTIR和储氢性能测试手段等对复合体系结构和储氢性能进行表征,研究了不同Ce基催化剂对复合体系放氢性能的影响,分析了催化剂的催化机理。结果表明:2LiBH4/MgH2复合物加热过程为明显的两步放氢,第1步主要发生MgH2的分解放氢;第2步为第1步生成的Mg与LiBH4发生放氢反应;添加Ce和CeF3都能提高2LiBH4/MgH2体系的放氢性能。Ce主要改善体系第2步放氢特性,CeF3对体系两步放氢反应均产生显著效果。添加5mol%CeF3使2LiBH4/MgH2体系起始放氢温度降低约100℃,体系最大放氢量达到10.6%(质量分数,下同);F-取代部分H-形成LiBH1-xFx,改善了LiBH4的分解特性,从而显著改善了2LiBH4/MgH2体系的放氢性能。

2LiBH4/MgH2 hydrogen storage composite was prepared by ball-milling technology,and its microstructures and hydrogen storage properties were characterized by X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FTIR） and hydrogen storage measurements.The effects of Ce-based catalysts on the hydrogen storage properties of the composite were studied.The results show that hydrogen release of 2LiBH4/MgH2 composite is a two-step process,i.e.,the first is the decomposition of MgH2 and the second is the reaction between LiBH4 and Mg just produced.Ce or CeF3 addition can improve the dehydrogenation of 2LiBH4/MgH2 composite.Ce mainly improves the behavior of the second step reaction while CeF3 influences the behavior of the two steps greatly.For the 2LiBH4/MgH2 composite with addition of 5 mol% CeF3,the total hydrogen capacity reaches 10.6 wt% at 450 oC and the initial hydrogen release temperature is decreased by around 100 oC.LiBH1-xFx is formed by partial substitution of F-for H-,which decreases the decomposition temperature of LiBH4.