MgH2+20%(w)MgTiO3复合材料的吸/放氢性能

为了降低MgH₂的吸放氢温度, 提高其吸放氢动力学性能, 本文通过球磨方法制备了MgH₂+20%(w)MgTiO₃复合储氢材料, 并研究了其储氢性能. X射线衍射(XRD)结果表明, MgTiO₃在与MgH₂球磨过程中生成Mg₂TiO₄和TiO₂, 并且Mg₂TiO₄和TiO₂在体系的吸放氢过程中保持稳定, 能够对MgH₂的吸放氢过程产生催化作用. 程序升温脱附和吸/放氢动力学测试结果表明, 添加MgTiO₃后MgH₂的初始放氢温度从389 ℃降至249 ℃.150 ℃下的吸氢量从0.977%(w)提高到2.902%(w), 350 ℃下的放氢量从2.319%(w)提高到3.653%(w). 同时, MgH₂放氢反应的活化能从116 kJ·mol^-1降至95.7 kJ·mol^-1. 与MgH₂相比, MgH₂+20%(w) MgTiO₃复合材料的热力学与动力学性能均有显著提高, 这主要是由于球磨和放氢过程中原位生成的TiO₂和Mg₂TiO₄具有良好的催化活性.

Hydriding/Dehydriding Properties of an MgH2+20%(w) MgTiO3 Composite

With the aim of decreasing the dehydriding temperature and improving the hydriding/dehydriding kinetic properties of MgH₂, we prepared MgH₂+20%(w) MgTiO₃ composite via ball-milling, and investigated the hydrogen storage properties of the composite. X- ray diffraction (XRD) results showed that the MgTiO₃ decomposed into Mg₂TiO₄ and TiO₂ during the ball-milling. These two resulting compounds remained stable during the hydriding/dehydriding processes, working as catalysts for the hydriding/dehydriding. Temperatureprogrammed- desorption (TPD) and hydriding/dehydriding kinetics tests showed that doping MgH₂ with MgTiO₃ lowered the onset dehydrogenation temperature of MgH₂ from 389 to 249 ℃, as well as increasing the hydrogen absorption amount from 0.977%(w) to 2.902%(w) at 150 ℃, and increasing the desorption amount from 2.319% (w) to 3.653%(w) at 350 ℃. The MgTiO₃ additive decreased the dehydriding activation energy of MgH₂ from 116 to 95.7 kJ·mol^-1. The thermodynamic and kinetic performance of the MgH₂+20%(w) MgTiO₃ composite was significantly improved compared with pristine MgH₂, which was attributed to the high catalytic activity of the (insitu formed) TiO₂ and Mg₂TiO₄ during the ball-milling and dehydriding processes.