Wang Jianhui, Chen Ping, Pan Hongge, Xiong Zhitao, Gao Mingxia, Wu Guotao, Liang Chu, Li Cao, Li Bo, Wang Jieru
State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (PR China), Fax: (+86) 411-84685940; Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (PR China).
ChemSusChem. 2013 Nov;6(11):2181-9. doi: 10.1002/cssc.201200885. Epub 2013 Jul 31.
Considerable efforts have been devoted to the catalytic modification of hydrogen storage materials. The K-modified Mg(NH2 )2 /2 LiH composite is a typical model for such studies. In this work, we analyze the origin of the kinetic barrier in the first step of the dehydrogenation and investigate how K catalyzes this heterogeneous solid-state reaction. Our results indicate that the interface reaction of Mg(NH2 )2 and LiH is the main source of the kinetic barrier at the early stage of the dehydrogenation for the intensively ball-milled Mg(NH2 )2 /2 LiH sample. K can effectively activate Mg(NH2 )2 as well as promote LiH to participate in the dehydrogenation. Three K species of KH, K2 Mg(NH2 )4 , and Li3 K(NH2 )4 likely transform circularly in the dehydrogenation (KH↔K2 Mg(NH2 )4 ↔KLi3 (NH2 )4 ), which creates a more energy-favorable pathway and thus leads to the overall kinetic enhancement. This catalytic role of K in the amide/hydride system is different from the conventional catalysis of transition metals in the alanate system.
人们已在储氢材料的催化改性方面付出了巨大努力。钾改性的Mg(NH₂)₂/2LiH复合材料就是此类研究的典型范例。在这项工作中，我们分析了脱氢第一步中动力学势垒的来源，并研究了钾如何催化这种多相固态反应。我们的结果表明，对于经过强烈球磨的Mg(NH₂)₂/2LiH样品，Mg(NH₂)₂与LiH的界面反应是脱氢早期动力学势垒的主要来源。钾可以有效活化Mg(NH₂)₂，并促进LiH参与脱氢反应。三种钾物种KH、K₂Mg(NH₂)₄和Li₃K(NH₂)₄可能在脱氢过程中循环转化（KH↔K₂Mg(NH₂)₄↔KLi₃(NH₂)₄），这创造了一条能量更有利的途径，从而导致整体动力学增强。钾在酰胺/氢化物体系中的这种催化作用不同于过渡金属在铝酸盐体系中的传统催化作用。
