(1. 湖南大學(xué) 汽車車身先進(jìn)設(shè)計制造國家重點實驗室，長沙 410082；
2. 張家界航空工業(yè)職業(yè)技術(shù)學(xué)院 航空維修系，張家界 427000)
摘 要: 基于TiF3作為催化劑提高M(jìn)gH2解氫性能的實驗結(jié)果，采用基于密度泛函理論的Dmol3程序包，計算從MgH2體系中移走H原子所需能量及幾何、電子結(jié)構(gòu)的改變，探討TiF3對MgH2體系解氫熱力學(xué)影響及提高其解氫性能的機理。結(jié)果表明:Ti替代Mg，體系中Ti—H的成鍵作用比Mg-H強，Ti將MgH2中的H吸附到其周圍，導(dǎo)致MgH2中Mg周圍的H減少；創(chuàng)造Mg空位，隨著溫度的提高，體系中H—H之間的鍵長變短，兩者情形均利于提高M(jìn)gH2體系的熱力學(xué)行為。創(chuàng)造Mg空位所需能量(6.65 eV)高于Ti替代Mg的能量(2.34 eV)，表明低溫下，Ti替代Mg對MgH2體系解氫更為有利，至此TiF3中的Ti替代MgH2中的Mg，利于加快化學(xué)反應(yīng)的進(jìn)行，使結(jié)構(gòu)穩(wěn)定的MgH2發(fā)生轉(zhuǎn)變，生成結(jié)構(gòu)不穩(wěn)定的TiH2，這樣體系解氫過程不是通過MgH2，而是轉(zhuǎn)化為TiH2進(jìn)行，因此TiF3可提高M(jìn)gH2體系的解氫性能。
關(guān)鍵字: MgH2；TiF3；密度泛函理論；解氫性能
（1. State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body,
Hunan University, Changsha 410082, China;
2. Zhangjiajie Aviation Industry Vocational Technical College of
Aviation Maintenance Department, Zhangjiajie 427000, China）
Abstract:Based on experimental results in which the dehydrogenating properties of MgH2 systems was improved by the addition of TiF3 as the catalyst, the energy to remove H atoms, geometry and electronic structure of MgH2 systems were calculated by using Dmol3 program based on the density functional theory. Solutions for MgH2 hydrogen doping TiF3 thermodynamic effects were studied.The results show that the role of Ti—H bond is stronger than the effect of Mg—H bond, thus the H atoms around Mg atoms in MgH2 phase diffuse to the Ti atom around, resulting in reduction of the H atoms around Mg. The formation of Mg vacancy can improve the thermodynamic behavior of MgH2 system. At low temperatures, the Ti atoms of TiF3 can substitution some Mg atoms of MgH2 system, which occupy the larger advantage for the formation of Mg vacancies. The dehydrogenating properties of MgH2 systems is improved with TiF3 because of the Ti atoms of TiF3 substitution the Mg atoms of MgH2 system formed TiH2, the reaction of 2TiF3+3MgH2→3MgF2+2TiH2+H2 during mill process is accelerated, and a stable structure MgH2 shift, generating unstable structure TiH2, this system is not the solution process by MgH2, but converts to TiH2, so TiF3 can improve the performance of hydrogen.
Key words: MgH2; TiF3; density functional theory; dehydrogenating property
