本文選題：納米貴金屬 + 核殼結(jié)構(gòu)��； 參考：《上海師范大學(xué)》2017年碩士論文

【摘要】：納米貴金屬催化劑,特別是金催化劑,由于存在尺度效應(yīng),當其顆粒大小小于5 nm時,將表現(xiàn)出很強的催化活性。但是負載型的貴金屬催化劑由于納米粒子其表面原子占有的體積比非常大,表面原子配位不足具有非常高的表面能,從而使得相鄰的金納米粒子容易團聚,而導(dǎo)致催化劑失活。要維持催化劑的催化活性,可以采用在納米空間上進行物理隔離的方式,將金納米粒子相互間距離拉遠,避免發(fā)生遷移團聚。常用合成材料的方法是將納米貴金屬粒子通過包裹的方式分散在另一種材料內(nèi)部,通過構(gòu)建核殼結(jié)構(gòu)來保護納米貴金屬粒子不發(fā)生團聚。我們選擇了三種核殼結(jié)構(gòu)來比較不同核殼結(jié)構(gòu)的特性,并以一氧化碳催化氧化反應(yīng)作為探針反應(yīng)評價催化劑反應(yīng)性能。本論文第一部分采用微乳液的合成方式,一鍋法合成了一種二氧化硅包裹的金納米粒子材料Au@SiO_2,該材料具有均勻的結(jié)構(gòu),其中金納米粒子顆粒大小為2.3±0.5 nm,二氧化硅殼層半徑為10 nm。該材料用于一氧化碳氧化時,起始反應(yīng)溫度為230℃。400℃下反應(yīng)65小時,轉(zhuǎn)化率只有小幅下降,由83.4%降至80.5%,材料穩(wěn)定性優(yōu)良。第二部分以第一部分材料為硬模板,經(jīng)水熱合成后刻蝕除去模板,得到多孔腔二氧化鈰包裹的催化劑Au@HM-CeO_2,該催化劑初始催化活性高,通過調(diào)節(jié)金納米粒子的大小,當金納米粒子大小為4 nm時,催化劑穩(wěn)定性優(yōu)異,在250℃反應(yīng)225小時催化劑活性幾乎保持不變。第三部分采用分子篩作為包裹材料,以巰基硅烷鍵合保護貴金屬,得到原位的包裹,同時利用熱變性水凝膠作為硬模板,合成納米分子篩包裹的催化劑Au@nano-LTA及Au-Pt@nano-LTA。由于分子篩的孔徑介于二氧化硅與二氧化鈰包裹材料之間,既能有效包裹納米貴金屬粒子,同時又保證催化劑與反應(yīng)物分子的有效接觸。其中催化劑Au-Pt@nano-LTA具有本章中最佳的催化活性及穩(wěn)定性。
[Abstract]:Nanocrystalline noble metal catalysts, especially gold catalysts, show strong catalytic activity when the particle size is less than 5 nm due to the existence of scale effect. However, the supported noble metal catalyst has high surface energy due to its large volume ratio of surface atoms, which leads to the agglomeration of the adjacent gold nanoparticles and the deactivation of the catalyst. In order to maintain the catalytic activity of the catalyst, the gold nanoparticles can be separated from each other by physical isolation in nanospace to avoid migration and agglomeration. The common method of synthesizing materials is to disperse nano-precious metal particles in another material by encapsulation, and to construct core-shell structure to protect nano-precious metal particles from agglomeration. Three core-shell structures were selected to compare the characteristics of different core-shell structures and the catalytic oxidation of carbon monoxide was used as a probe to evaluate the catalytic performance of the catalyst. In the first part of this thesis, a silica coated gold nanoparticle material Aur @ SiO-2 was synthesized by one-pot method using microemulsion. The material has a uniform structure, in which the particle size of gold nanoparticles is 2.3 鹵0.5 nm, and the radius of silica shell is 10 nm. When the material was used for CO oxidation, the initial reaction temperature was 230 鈩，

本文編號：2030686