Mechanism of improving hydrogenation of Mg by in-situ formation of Al* in hydriding combustion synthesis
Mechanism of improving hydrogenation of Mg by in-situ formation of Al* in hydriding combustion synthesis
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DOI：
10.1016/j.jallcom.2022.164969
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发表时间：
2022-04
影响因子：
6.2
通讯作者：
Shujing Li;Lili Yang;Yunfeng Zhu;Yana Liu;Jiguang Zhang;Liquan Li
中科院分区：
文献类型：
--
作者：
Shujing Li;Lili Yang;Yunfeng Zhu;Yana Liu;Jiguang Zhang;Liquan Li
氢化镁（MgH 2）是一种理想的固体储氢材料和在线水解氢源。但MgH 2的合成通常需要高温、高压和长时间的苛刻条件，给生产成本和安全性带来了极大的挑战。本文采用间歇燃烧合成法（HCS）制备了MgH 2，并揭示了原位生成Al* 改善Mg加氢性能的机理。在1 MPa的低氢压下，加入10mol%Al，可使Mg的氢化度由纯Mg的9.6%提高到90.5%。在激活阶段，Al与Mg反应生成Mg 17 Al 12，这带来了丰富的晶界，为氢提供了快速扩散通道。随后，在氢化阶段，Mg 17 Al 12与H2反应以原位生成Al*，其均匀分布并充当MgH 2的形核位点。氢分子沿着Mg/MgH 2与Al* 的界面迅速扩散，容易在纳米Al* 表面吸附和解离。原位形成高活性金属物质作为优良催化剂的独特的加氢反应为镁基储氢材料的改性提供了新的思路。
Magnesium hydride (MgH2) is an ideal solid hydrogen storage material and on-line hydrolysis hydrogen source. However, the synthesis of MgH2usually requires harsh conditions of high temperature, high pressure and long duration, bringing great challenges to production cost and safety. In this paper, MgH2is prepared by hydriding combustion synthesis (HCS) and the mechanism of improving Mg hydrogenation properties by the in-situ formation of Al* is revealed. Under low hydrogen pressure of 1 MPa, the hydrogenation degree of Mg can be greatly increased from 9.6% of pure Mg to 90.5% with 10 mol% Al added. In the activation stage, Al reacts with Mg to form Mg17Al12, which brings rich grain boundaries and provides rapid diffusion channels for hydrogen. Subsequently, in the hydrogenation stage, Mg17Al12reacts with H2to generate Al* in-situ, which are evenly distributed and act as nucleation sites for MgH2. Hydrogen molecules diffuse rapidly along the interface between Mg/MgH2and Al* and are easily adsorbed and dissociated on the surface of nano-scale Al* . The unique disproportionation hydrogenation reaction of in-situ forming highly active metallic substances as excellent catalysts provides a new idea for the modification of Mg-based hydrogen storage materials.