【摘要】：貴金屬鈀、鉑催化性能優(yōu)異,是工業(yè)生產(chǎn)中重要的金屬催化劑。為解決鈀、鉑儲量稀少的問題,我們發(fā)展了膠體化學(xué)方法制備了鈀銀、鉑錫納米晶,并將其分別用于催化加氫反應(yīng)及電催化甲酸氧化反應(yīng),其優(yōu)異的催化性能使鈀、鉑資源的高效利用成為可能。雙金屬納米晶的催化性質(zhì)與納米晶尺寸、形貌、組成等結(jié)構(gòu)因素密切相關(guān),因此,發(fā)展高效催化劑依賴于對反應(yīng)的深入理解和可控的納米合成技術(shù)。本論文通過可控的改變鈀銀、鉑錫納米晶的組成,顯著地提高了催化劑的活性和反應(yīng)的區(qū)域選擇性,并經(jīng)過系統(tǒng)的表征手段加深了對催化劑結(jié)構(gòu)-性質(zhì)關(guān)系的認(rèn)識。制備了優(yōu)異的脫氯加氫催化劑——鈀銀合金納米晶。在十八胺體系,合成了一系列具有不同比例,尺寸均一的鈀銀合金納米晶。通過對不同時(shí)間鈀銀合金納米晶產(chǎn)物的表征,我們研究了納米晶的生長過程。此系列納米晶的催化活性在催化4-氯苯酚的脫氯加氫反應(yīng)中展現(xiàn)了顯著的組成依賴性,明確了鈀、銀在催化加氫過程中的不同作用,為設(shè)計(jì)更好的環(huán)境保護(hù)催化劑提供了依據(jù)。制備了尺寸均一的不同組成的鉑錫納米晶,并將其應(yīng)用于α,β不飽和醛的羰基選擇性加氫反應(yīng)中。X射線表征揭示鉑錫納米晶的結(jié)構(gòu)隨著錫含量增加發(fā)生的變化:由氧化錫“補(bǔ)丁”的鉑錫合金轉(zhuǎn)變?yōu)檠趸a“補(bǔ)丁”的鉑團(tuán)簇。在肉桂醛的催化加氫過程中,隨著錫含量的增加,目標(biāo)產(chǎn)物不飽和醇的選擇性增加,而催化活性呈現(xiàn)出先增加后降低的特點(diǎn)。實(shí)驗(yàn)證明鉑在反應(yīng)中起到解離氫的作用,而密度泛函理論計(jì)算表明氧化錫中的氧缺陷在促進(jìn)羰基吸附中起到了決定性作用。此課題研究了“組成-結(jié)構(gòu)-性質(zhì)”的關(guān)系,為生物質(zhì)轉(zhuǎn)化催化劑的合成提供了思路。探索了低溫一步合成鉑錫金屬間化合物技術(shù),制備并研究了凹面立方體和多缺陷立方體的Pt3Sn形成的機(jī)理。不同形貌的Pt3Sn顯示出不同的電催化甲酸氧化活性,由于結(jié)合了金屬間化合物的穩(wěn)定性和缺陷的活性,多缺陷立方體Pt3Sn的活性與抗中毒性最好。此項(xiàng)研究改善了金屬間化合物形貌控制研究稀少的現(xiàn)狀,為金屬間化合物的催化應(yīng)用提供了物質(zhì)基礎(chǔ)。
[Abstract]:Noble metal palladium and platinum have excellent catalytic performance and are important metal catalysts in industrial production. In order to solve the problem of scarce storage of palladium and platinum, we developed colloidal chemical methods to prepare palladium silver and platinum tin nanocrystals, and used them for catalytic hydrogenation and electrocatalytic formic acid oxidation respectively. The efficient utilization of platinum resources is possible. The catalytic properties of bimetallic nanocrystals are closely related to the structural factors such as size, morphology and composition of nanocrystals. Therefore, the development of efficient catalysts depends on in-depth understanding of the reaction and controllable nanosynthesis technology. By changing the composition of Pd-Ag and Pt-Sn nanocrystals, the activity of the catalyst and the regional selectivity of the reaction were improved significantly, and the relationship between the structure and the properties of the catalyst was further understood by means of systematic characterization. Palladium silver alloy nanocrystalline was prepared as an excellent catalyst for dechlorination hydrogenation. In octadecylamine system, a series of palladium silver alloy nanocrystals with different proportion and uniform size were synthesized. The growth process of palladium silver alloy nanocrystals was studied by characterization of nanocrystalline products at different times. The catalytic activity of this series of nanocrystals in the dechlorination hydrogenation of 4-chlorophenol showed a significant component dependence, and the different roles of palladium and silver in the catalytic hydrogenation process were clarified. It provides a basis for the design of better environmental protection catalyst. Pt-Sn nanocrystals with uniform size were prepared and applied to 偽. In the carbonyl selective hydrogenation of 尾 -unsaturated aldehydes, X-ray characterization revealed that the structure of platinum and tin nanocrystals changed with the increase of tin content: from the "patch" of tin oxide to the platinum cluster of "patch" of tin oxide. In the process of catalytic hydrogenation of cinnamaldehyde, the selectivity of unsaturated alcohols increased with the increase of tin content, while the catalytic activity increased first and then decreased. The experimental results show that platinum plays a role of dissociation hydrogen in the reaction, and density functional theory shows that oxygen defects in tin oxide play a decisive role in promoting carbonyl adsorption. The relationship between composition, structure and property is studied in this paper, and the synthesis of catalyst for material transformation is provided. The technology of one-step synthesis of platinum-tin intermetallic compounds at low temperature was explored. The formation mechanism of Pt3Sn for concave cube and multi-defect cube was prepared and studied. Different morphologies of Pt3Sn showed different electrocatalytic formic acid oxidation activity. Because of the combination of intermetallic compound stability and defect activity, multi-defect cube Pt3Sn had the best activity and anti-toxicity. This study improves the present situation of morphology control of intermetallic compounds and provides a material basis for the catalytic application of intermetallic compounds.
【學(xué)位授予單位】：清華大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：O643.36;TB383.1

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