固溶体MAX相(Ti_(0.5)V_(0.5))_3AlC_2的制备及其对MgH_2储氢性能的催化影响

Synthesis and Catalytic Effects of Solid-Solution MAX-phase(Ti_(0.5)V_(0.5))_3AlC_2 on Hydrogen Storage Performance of MgH_2

通过无压烧结法制备了固溶体MAX相(Ti_(0.5)V_(0.5))_3AlC_2,研究了其添加对MgH_2储氢性能的影响。结果发现,固溶体MAX相(Ti_(0.5)V_(0.5))_3AlC_2中的Ti和V元素通过协同作用,呈现出更高的催化活性。添加质量分数10%(Ti_(0.5)V_(0.5))_3AlC_2的MgH_2样品的起始放氢温度为230℃,较原始MgH_2降低了60℃。在275℃下等温放氢,(Ti_(0.5)V_(0.5))_3AlC_2添加样品的放氢速率可达0.35%·min^(-1),是原始MgH_2样品的4倍左右。此外,完全放氢后的MgH_2-10%(Ti_(0.5)V_(0.5))_3AlC_2样品在150℃、5 MPa氢压下,可在60 s内吸收4.7%的氢。计算显示,MgH_2-10%(Ti_(0.5)V_(0.5))_3AlC_2样品的表观活化能为79.6 kJ·mol^(-1),较原始MgH_2(153.8 kJ·mol^(-1))降低了48%,这是MgH_2放氢性能得到改善的主要原因。

A solid-solution MAX phase (Ti0.5V0.5)3AlC2 was successfully synthesized with a pressureless sintering method, and its catalytic effect on hydrogen storage reaction of MgH2 was systematically investigated. The solid solution MAX phase (Ti0.5V0.5)3AlC2 exhibited superior catalytic activity, thanks to the synergistic catalysis effect of Ti and V. The on-set dehydrogenation temperature of MgH2-10%(Ti0.5V0.5)3AlC2 samples was only 230 ℃(mass fraction of (Ti0.5V0.5)3AlC2 was 10%), which was 60 ℃ lower than that of pristine MgH2. The desorption rate of MgH2-10%(Ti0.5V0.5)3AlC2 sample at 217 ℃ was calculated to be 0.35%·min^-1, which was 4 times faster than that of the pristine sample. At 150 ℃, the dehydrogenated MgH2-10%(Ti0.5V0.5)3AlC2 sample absorbs 4.7% of H2 within 60 s under 5 MPa H2. The apparent activation energy of the MgH2-10%(Ti0.5V0.5)3AlC2 sample was determined to be 79.6 kJ·mol^-1, representing a 48% reduction in the reaction barrier, compared with pristine MgH2 (153.8 kJ·mol^-1). This reasonably explains the significant improvement in dehydrogenation performance.