本文選題：超細氧化銅　切入點：合金納米晶　出處：《清華大學》2015年博士論文　論文類型：學位論文

【摘要】：納米材料在催化領(lǐng)域的應用已成為當前納米科學研究的熱點之一。納米材料的催化性質(zhì)與其形貌、尺寸、組成等因素密切相關(guān)。因此,納米合成技術(shù)的發(fā)展及對催化劑構(gòu)效關(guān)系本質(zhì)的深入理解有助于新型高效催化劑的開發(fā)。本論文以銅基、鉑基納米材料(氧化銅、銅單質(zhì)、金屬鉑、鉑基雙金屬)為研究對象,圍繞當前納米催化劑合成存在的挑戰(zhàn),以液相合成法為手段,探索了具有特殊形貌催化劑的制備方法、形成機制,并對其結(jié)構(gòu)與性能之間的相關(guān)性進行了深入研究。納米材料催化性能研究發(fā)現(xiàn),高指數(shù)晶面比低指數(shù)晶面具有更好的催化活性。但目前具有高指數(shù)晶面納米晶的研究主要集中于貴金屬,對多組分且對稱性較低的金屬氧化物,報道較少。本論文第一部分工作選擇了具有單斜結(jié)構(gòu)的氧化銅為研究對象,利用油胺分子的特異性吸附,制備暴露高指數(shù)晶面的超細氧化銅納米棒。該材料在催化苯乙烯環(huán)氧化生成環(huán)氧苯乙烷具有很高的活性和選擇性。該方法可為合成其他高指數(shù)晶面的氧化物提供新思路。目前,無機類富勒烯結(jié)構(gòu)納米材料的制備僅限于自身具有層狀結(jié)構(gòu)的無機材料。由于缺少在三維空間折疊的驅(qū)動力,利用非層狀材料合成類富勒烯結(jié)構(gòu)一直是研究的難點。本論文第二部分工作利用十六胺在水中形成膠束,在組裝成類富勒烯結(jié)構(gòu)的同時,原位還原金屬離子,成功制備了類富勒烯狀的Pt-Cu合金納米晶。通過球差電鏡分析發(fā)現(xiàn),該結(jié)構(gòu)的形成是通過兩種機制實現(xiàn)的:一種是大角度彎曲形成折線,通過產(chǎn)生孿晶界釋放彎曲過程中產(chǎn)生的應力。另一種是在折線處,通過晶格膨脹或收縮引發(fā)小角度彎曲,從而形成曲線。這些結(jié)構(gòu)缺陷的存在使該材料在電催化氧化甲醇乙醇,環(huán)加成反應均表現(xiàn)出比商業(yè)催化劑更優(yōu)異的性質(zhì)。高度支化的納米材料,由于具有較大的比表面積,豐富的邊、角和臺階原子,使得該材料在催化領(lǐng)域展現(xiàn)出良好的應用前景。然而大多數(shù)貴金屬具有高度對稱的面心立方結(jié)構(gòu),所以制備具有各向異性結(jié)構(gòu)的納米晶成為了一大挑戰(zhàn)。本論文最后一部分工作利用界面合成的方法,以十六胺和水界面處形成的多枝狀膠束為模板,制備出了具有規(guī)則結(jié)構(gòu)的超細多枝狀Pt納米晶。通過對不同反應時間的觀察,發(fā)現(xiàn)取向連接是形成該結(jié)構(gòu)的主要原因。這種表面支化的材料在對氯硝基苯選擇性還原反應中體現(xiàn)出較好的催化活性。
[Abstract]:The application of nanomaterials in the field of catalysis has become one of the hotspots in nanoscience research. The catalytic properties of nanomaterials are closely related to their morphology, size, composition and other factors. The development of nanosynthesis technology and the understanding of the nature of catalyst structure-activity relationship are helpful to the development of novel and high-efficient catalysts. In this thesis, copper based and platinum based nanomaterials (copper oxide, copper oxide, platinum, platin-based bimetallic) are studied. According to the existing challenges in the synthesis of nanocrystalline catalysts, the preparation and formation mechanism of catalysts with special morphology were explored by the method of liquid phase synthesis. The correlation between structure and performance was studied. The catalytic properties of nanomaterials were found. The high index crystal face has better catalytic activity than the low index crystal mask, but the research of nanocrystalline with high index crystal surface is mainly focused on precious metal, and it is more suitable for metal oxides with low symmetry and multicomponent. In the first part of this thesis, copper oxide with monoclinic structure was selected as the research object, and the specific adsorption of oleamine molecule was used. Ultrafine copper oxide nanorods exposed to high index crystal planes were prepared. The materials have high activity and selectivity in the catalytic epoxidation of styrene to epoxy-phenylethane. This method can provide a new idea for the synthesis of other oxides with high index crystal faces. The preparation of inorganic fullerene-like nanomaterials is limited to inorganic materials with layered structure. The synthesis of fullerene-like structure from non-layered materials has been a difficult point. In the second part of this thesis, 16 amines were used to form micelles in water, and the structure of fullerenes was assembled and metal ions were reduced in situ. Fullerene-like nanocrystals of Pt-Cu alloys were successfully prepared. By spherical differential electron microscopy analysis, it was found that the formation of the structure was realized by two mechanisms: one was the large angle bending to form a broken line, The curve is formed by creating twinning boundaries to release the stresses generated during bending. The other is to form curves at the broken line by lattice expansion or contraction, resulting in small angle bending. The existence of these structural defects causes the material to electrocatalyze the oxidation of methanol and ethanol. The cycloaddition reactions exhibit better properties than commercial catalysts. Highly branched nanomaterials, due to their large specific surface area, rich edge, angle and step atoms, However, most of the precious metals have a highly symmetrical face-centered cubic structure. Therefore, the preparation of anisotropic nanocrystals has become a challenge. In the last part of this thesis, the multi-dendritic micelles formed at the interface of 16 amine and water were used as templates in the last part of this thesis. Ultrafine multi-branched Pt nanocrystals with regular structure were prepared. It was found that the orientation connection was the main reason for the formation of the structure, and the surface branched material showed good catalytic activity in the selective reduction of p-chloronitrobenzene (p-chloronitrobenzene).
【學位授予單位】：清華大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TB383.1;O643.36

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