金属@二氧化硅核壳纳米结构合成及其催化氨硼烷制氢

发布时间：2018-05-16 04:11

本文选题：核壳纳米粒子 + 氨硼烷　；参考：《江西师范大学》2015年硕士论文

【摘要】：近年来,氢气作为全球公认的清洁能源载体,备受关注和重视。发展安全高效的储氢材料仍然是氢经济社会的最大挑战之一。氨硼烷由于高储氢量、环境友好性等优点成为极具潜在应用价值的储氢材料之一。目前,氨硼烷水解反应的催化剂大部分是单金属、双金属或者三金属,这些金属纳米催化剂由于直接裸露在反应体系中会出现聚集现象而导致其活性降低,甚至失活。因此,寻求一种高效稳定的催化剂成为目前研究的热点。本文主要围绕以二氧化硅为壳均匀包裹金属纳米粒子的制备、表征以及催化性能展开研究,主要内容如下:在非离子表面活性剂壬基酚聚氧乙烯醚(NP-5)/环己烷反胶束体系中,以K2PtCl4为前驱体,合成了嵌入二氧化硅纳米球中尺寸约为4 nm的超细Pt纳米粒子(Pt@SiO2)。与单金属Pt纳米粒子和负载型Pt/SiO2纳米粒子相比较,Pt@SiO2核壳纳米催化剂在催化氨硼烷水解制氢过程中表现出了更优的催化性能,其TOF值为158.6 mol H2(mol Pt min)-1,在已报道的Pt基催化剂中属于比较高的值。经过循环使用以及高温处理测试,Pt@SiO2核壳纳米结构的形貌和催化活性都没有明显变化,表现出优异的稳定性。在反胶束微乳液体系中,以Co(NH3)6Cl3为前驱体,制备Co@SiO2核壳纳米粒子。利用简单的化学浸渍法,采用氨硼烷作为还原剂,成功地一步原位还原制备Ag/Co@SiO2纳米复合催化剂,同时催化氨硼烷水解制氢。其催化性能优于单金属Ag纳米粒子,SiO2负载的Ag纳米粒子(Ag/SiO2),单独的Co@Si O2核壳纳米粒子以及物理混合的Ag和Co@SiO2纳米粒子。通过测试不同温度下的催化活性,得出其反应活化能为24.9 k J mol-1,较低于其他报道过的双金属催化剂的活化能值。常温常压下循环使用5次后,其催化性能没有明显的降低,表明了该催化剂具有较好的循环稳定性。
[Abstract]:In recent years, hydrogen, as a globally recognized carrier of clean energy, has attracted much attention. The development of safe and efficient hydrogen storage materials remains one of the biggest challenges of hydrogen economy and society. Because of its high hydrogen storage capacity and environmental friendliness, aminoborane has become one of the potential hydrogen storage materials. At present, the catalysts for hydrolysis of ammonium-borane are mostly monometallic, bimetallic or trimetallic, and these metal nanocatalysts decrease or even deactivate due to the aggregation phenomenon of direct exposure in the reaction system. Therefore, the search for a high-efficient and stable catalyst has become the focus of research. In this paper, the preparation, characterization and catalytic properties of metal nanoparticles coated with silicon dioxide as shell are studied. The main contents are as follows: in Nonionic surfactant NP-5 / cyclohexane reverse micelle system, Ultrafine Pt nanoparticles with the size of about 4 nm have been synthesized by using K2PtCl4 as precursor and embedded in silica nanospheres. Compared with monometallic Pt nanoparticles and supported Pt/SiO2 nanocrystalline catalysts, the catalytic performance of PTB / SiO2 core-shell nanocrystalline catalysts is better than that of Pt nanoparticles and supported Pt/SiO2 nanoparticles in the process of hydrolysis of aminoborane to produce hydrogen. Its TOF value is 158.6 mol H2(mol Pt min-1, which is a relatively high value in the reported Pt based catalysts. The morphology and catalytic activity of Pt@ Sio _ 2 core-shell nanostructures have not changed obviously after recycling and high temperature treatment, showing excellent stability. Co@SiO2 core-shell nanoparticles were prepared by using Co(NH3)6Cl3 as precursor in reverse micelle microemulsion system. Ag/Co@SiO2 nanocomposite catalyst was successfully prepared by one step in situ reduction with aminoborane as reductant by a simple chemical impregnation method. At the same time, it catalysed hydrolysis of aminoborane to produce hydrogen. Its catalytic performance is superior to that of Ag / Sio _ 2-supported Ag nanoparticles, single Co@Si O _ 2 core-shell nanoparticles and physical mixed Ag and Co@SiO2 nanoparticles. The activation energy of the catalyst is 24.9 kJ mol-1, which is lower than that of other bimetallic catalysts. After 5 cycles at room temperature and atmospheric pressure, the catalytic performance of the catalyst was not obviously decreased, which indicated that the catalyst had better cycle stability.
【学位授予单位】：江西师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ116.2;O643.36

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