络合氢化物Ti-NaAlH_4的制备与储氢特性

Preparation and Hydrogen Storage Characteristics of Ti-NaAlH_4 Complex Hydride

采用Ti粉为催化剂前驱体、预处理Al粉和NaH为合成原料,通过机械球磨-加氢方法合成出络合氢化物Ti-NaAlH4,系统研究了球磨保护气氛、球磨时间和氢化加氢压力等制备参数对其储氢性能的影响.结果表明,制备方法对Ti-NaAlH4储氢特性有很大影响.与氩气保护气氛相比,在氢气气氛中球磨制备的复合物具有更高的吸放氢性能.在氢气保护气氛下,随着球磨时间从6h增至24h,复合物的吸氢容量和吸氢速率先增后减,12h时达到最佳值,而复合物的放氢容量和放氢速率则逐渐增高;进一步延长球磨时间会使颗粒发生团聚,从而导致吸氢性能下降.随着氢化加氢压力从7.5MPa升至13.5MPa,复合物的吸氢容量(质量分数)由2.83%逐渐增至4.21%.复合物球磨后出现的Na3AlH6中间氢化物相表明,在氢气下掺Ti球磨对NaH和Al的氢化反应起到很好的促进作用.

Ti-doped NaAlH4 complex hydride can be prepared by hydrogenation of the ball-milled （NaH/Al＋Ti） composite using NaH and preltreated Al powder as raw materials, and Ti powder as a dopant. The influence of preparation parameters （ball-milling atmosphere, milling time, and hydrogenation pressure） on its hydrogen storage characteristic has been investigated. It is found that the hydrogen storage properties are affected greatly by the preparation methods. The hydrogen storage properties of the composite ball-milled under hydrogen atmosphere are better than that of the composite ball-milled under argon atmosphere. With extending the milling time from 6 h to 24 h under hydrogen atmosphere, the hydrogen absorption capacity and rate increase first and then decrease, and the maximum values am obtained at 12 h, while the hydrogen desorption capacity and speed increase gradually. The particles of the composite will agglomerate when prolonging the milling-time over 12 h, which deteriorates the hydrogen absorption properties. As the hydrogenation pressure increases from 7.5 MPa to 13.5 MPa, the hydrogen absorption storage capacity （mass fraction） increases from 2.83% to 4.21%. The appearance of intermediate Na3AlH6 hydride phase in the ball-milled composite indicates that the Ti-doped （NaH/Al） composites ball-milled under hydrogen atmosphere can catalyze the hydrogenation reaction of Nail and AI.