貴金屬納米顆粒催化劑因其獨特的性質而備受關注。他們的高比表面積和可控的形貌使得他們表現出於同類體相材料所不同的催化性能。為了避免催化反應過程中由於納米顆粒本身形貌的改變而引起的催化活性降低，貴金屬納米顆粒通常被負載在固體氧化物載體上。同時，由於協同作用的產生，固體金屬氧化物載體在反應過程中也能對納米顆粒的催化效果產生影響。本論文系統介紹了利用超聲噴霧法製備貴金屬納米顆粒負載的金屬氧化物微納米球的過程，以及為研究這種微纳米球的催化性能而進行的實驗檢測。氧化物存在不仅为催化剂提供了载体，而且其介孔结构亦有利于反应物扩散到纳米催化剂的周围，从而提高反应的速率。 / 本論文首先介紹了一步法製備貴金屬納米顆粒負載的金屬氧化物微纳米球及其在催化反应中的應用。我們選擇了金、鉑和鈀來分別負載在二氧化鈦、二氧化鋯和三氧化二鋁微納米球上。這幾種貴金屬和氧化物都是在環境污染控制、石油化工產業和醫藥產業中具有代表性的催化劑及襯底。除了檢測我們所製備的微納米顆粒的結構形貌等特徵外，我們還利用對硝基苯酚還原為對胺基苯酚的這個催化反應檢驗了這些貴金屬納米顆粒負載的氧化物微納米球的催化活性。考慮到三種貴金屬和三種氧化物的排列組合，以及金屬含量可能產生的影響，我們準備了九類共18份樣品，逐個進行催化反應。最後的結果顯示，含鈀0.1%摩爾比例的二氧化鈦表現出最強的催化活性。同时，這種方法也可以推廣到其他的貴金屬以及氧化物襯底，從而可以簡單方便地製備各种氧化物负载貴金屬催化劑，并可以對他們之間的協同作用進行研究。 / 此外，我根據同樣的超聲噴霧法製備了貴金屬負載的空心介孔氧化物微納米球。這個研究課題引入了聚苯乙烯球作為模板。同時利用聚苯乙烯球表面修飾過的金屬納米顆粒之间的相互作用，實現了金屬納米顆粒在球表面的吸附，进而聚苯乙烯球可以作為載體將金屬納米顆粒帶入介孔氧化物中。通過熱分解將聚苯乙烯球除去後，金屬納米顆粒就可以吸附在空心介孔氧化物球的內表面。在這個實驗中，我們先製備好據有特殊形貌的金屬納米顆粒，比如金納米棒、鈀納米立方体和金納米棒外面包覆鈀的納米殼鞘結構。然後借助聚苯乙烯球將其帶入介孔二氧化鈦和二氧化鋯及二氧化硅中。在對硝基苯酚還原的實驗中，这种介孔微纳米球表现出良好的催化性能并在一定程度上提高了催化剂的循环性。 / 为了尽可能的提高催化剂的循环性，我希望能獲得據有良好磁性的介孔微納米球。我們嘗試了兩種方法，一是將磁性納米顆粒比如鐵的氧化物納米顆粒引入介孔氧化物微納米球，另一種方法是製備據有磁性的介孔氧化鐵微納米球。我们相信通過這種方法，貴金屬納米顆粒負載的介孔氧化物微納米球的催化性能，尤其是循環性能必然會顯著的提高。 / Noble metal nanoparticles/nanocrystals have attracted much attention as catalysts due to their unique characteristics, including high surface areas and well-controlled facets, which are not often possessed by their bulk counterparts. To avoid the loss of their catalytic activities brought about by their size and shape changes during catalytic reactions, noble metal nanoparticles/nanocrystals are usually dispersed and supported finely on solid oxide supports to prevent agglomeration, nanoparticle growth, and therefore the decrease in the total surface area. Moreover, metal oxide supports can also play important roles in catalytic reactions through the synergistic interactions with loaded metal nanoparticles/nanocrystals. In this thesis, I use ultrasonic aerosol spray to produce hybrid microspheres that are composed of noble metal nanoparticles/nanocrystals embedded in mesoporous metal oxide matrices. The mesoporous metal oxide structure allows for the fast diffusion of reactants and products as well as confining and supporting noble metal nanoparticles. / I will first describe my studies on noble metal-loaded mesoporous oxide microspheres as catalysts. Three types of noble metals (Au, Pt, Pd) and three types of metal oxide substrates (TiO₂, ZrO₂, Al₂O₃) were selected, because they are widely used for practical catalytic applications involved in environmental cleaning, pollution control, petrochemical, and pharmaceutical syntheses. By considering every possible combination of the noble metals and oxide substrates, nine types of catalyst samples were produced. I characterized the structures of these catalysts, including their sizes, morphologies, crystallinity, and porosities, and their catalytic performances by using a representative reduction reaction from nitrobenzene to aminobenzene. Comparison of the catalytic results reveals the effects of the different noble metals, their incorporation amounts, and oxide substrates on the catalytic abilities. For this particular reaction, I found that Pd nanoparticles supported on mesoporous TiO₂ exhibit the best catalytic performance. The demonstrated low-cost and high-productivity preparation method can be extended to other catalysts, which can contain various metals and oxide substrates and will have high potential for industrial applications. Our preparation method also provides a platform for the studies of the synergetic catalytic effects between different oxide substrates and metals. / I further fabricated hollow mesoporous microspheres containing differently shaped noble metal nanocrystals. Hollow structures are strongly desired in many applications because of their high pore volumes, surface areas, and possible light-trapping effect. In my study, the hollow structures were obtained by simply dispersing polystyrene (PS) nanospheres into the precursor solution for aerosol spray. The PS spheres were removed by thermal calcination to produce hollow mesoporous microspheres. In my first study, the noble metal salts were dissolved in the precursor solutions, and the noble metal nanoparticles were obtained through thermal calcination. In this way, the size and shape of the metal nanoparticles cannot be well controlled. In my second study, I first grew noble metal nanocrystals and then incorporated them into the oxide supports. This preparation route allowed me to incorporate metal nanocrystals with controlled sizes, shapes, and compositions into the oxide matrices. The metal nanocrystals I used in this experiment included Pd nanocubes, Au nanorods, and Au corePd shell nanorods. These nanocrystals were functionalized with thiol-terminated methoxypoly(ethylene glycol) . The surface functionalization allowed them to adsorb on the PS spheres. After thermal calcination, the noble metal nanocrystals were left inside and adsorbed on the inner surface of the hollow mesoporous metal oxide microspheres. I investigated the catalytic activities of the Pd nanocube-embedded hollow mesoporous TiO₂ and ZrO₂ microspheres for the reduction of 4-nitrophenol to 4-aminophenol. I also examined the recyclability of the Pd nanocube-embedded hollow mesoporous ZrO₂ microsphere catalysts. The results showed that the combination of the noble metal nanocrystals and oxides prevents the aggregation of the nanostructures and reduces the loss of the catalysts during the recycling processes, leading to the remarkable recyclability of the hybrid catalyst. This method for the preparation of noble metal nanostructure-embedded hollow mesoporous oxide microspheres can greatly facilitate the investigation on the catalytic properties of noble metal nanocrystal and metal oxide hybrid nanostructures and therefore guide the design and fabrication of high-performance catalysts. / Last but not least, I investigated the magnetic mesoporous microspheres to enable a better recyclability of the mesoporous oxide catalysts. Both magnetic nanoparticle-included mesoporous metal oxides and mesoporous magnetic oxides were presented. The successfully syntheses of these microspheres will greatly improve the catalytic performance of the noble metal nanoparticle-loaded mesoporous oxide microspheres. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Jin, Zhao = 貴金屬納米顆粒負載的介孔金屬氧化物微納米球及其催化應用 / 金釗. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Jin, Zhao = Gui jin shu na mi ke li fu zai de jie kong jin shu yang hua wu wei na mi qiu ji qi cui hua ying yong / Jin Zhao. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgement --- p.v / Table of Contents --- p.vii / List of Figures --- p.x / List of Tables --- p.xvii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Mesoporous metal oxide materials --- p.1 / Chapter 1.1.1 --- Overview on mesoporous materials --- p.1 / Chapter 1.1.2 --- Syntheses of mesoporous metal oxides --- p.3 / Chapter 1.1.2.1 --- Preparation of mesoporous metal oxides through soft-templating methods --- p.3 / Chapter 1.1.2.2 --- Preparation of mesoporous metal oxides through hard-templating methods --- p.8 / Chapter 1.1.3 --- Applications of mesoporous metal oxides --- p.11 / Chapter 1.1.3.1 --- Catalysis --- p.12 / Chapter 1.1.3.2 --- Energy conversion and storage --- p.13 / Chapter 1.1.3.3 --- Sensing --- p.13 / Chapter 1.2 --- Noble metal nanopartilces --- p.15 / Chapter 1.2.1 --- Overview of noble metal nanoparticles --- p.15 / Chapter 1.2.2 --- Catalytic applications of noble metal nanoparticles --- p.19 / Chapter 1.2.2.1 --- Automotive converter --- p.19 / Chapter 1.2.2.2 --- Suzuki cross-coupling reaction --- p.20 / Chapter 1.3 --- The overview of this thesis --- p.22 / References --- p.24 / Chapter 2 --- Ultrasonic Aerosol Spray --- p.30 / Chapter 2.1 --- Working principle and our ultrasonic aerosol spray system --- p.30 / Chapter 2.2 --- Materials synthesized by the AASA method --- p.34 / References --- p.37 / Chapter 3 --- Materials Characterization Methods and Catalytic Studies --- p.39 / Chapter 3.1 --- Characterization methods --- p.39 / Chapter 3.2 --- Model catalytic reaction --- p.41 / References --- p.45 / Chapter 4 --- Noble Metal Nanoparticle-Loaded Mesoporous Oxide Microspheres --- p.46 / Chapter 4.1 --- Experiments --- p.48 / Chapter 4.2 --- Results and discussion --- p.50 / Chapter 4.2.1 --- Mesoporous metal oxide microspheres --- p.50 / Chapter 4.2.2 --- Noble metal nanoparticle-loaded mesoporous oxide microspheres --- p.55 / Chapter 4.3 --- Summary --- p.73 / References --- p.75 / Chapter 5 --- Metal Nanostructure-Embedded Hollow Mesoporous Oxide Microspheres Prepared with Polystyrene Nanospheres as Carriers and Templates --- p.78 / Chapter 5.1 --- Experiments --- p.83 / Chapter 5.2 --- Results and discussion --- p.88 / Chapter 5.2.1 --- Hollow mesoporous oxide microspheres prepared with the PS spheres as templates --- p.88 / Chapter 5.2.2 --- Noble metal nanostructure-embedded hollow mesoporous oxide microspheres --- p.90 / Chapter 5.3 --- Summary --- p.106 / References --- p.108 / Chapter 6 --- Magnetic Mesoporous Microspheres --- p.113 / Chapter 6.1 --- Experiment --- p.115 / Chapter 6.2 --- Results and discussion --- p.117 / Chapter 6.2.1 --- Magnetic nanoparticle-included mesoporous TiO₂ microspheres --- p.117 / Chapter 6.2.2 --- Mesoporous iron oxide microspheres --- p.125 / Chapter 6.3 --- Summary --- p.128 / References --- p.130 / Chapter 7 --- Conclusions --- p.131
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_328165 |
| Date | January 2012 |
| Contributors | Jin, Zhao, Chinese University of Hong Kong Graduate School. Division of Materials Science and Engineering. |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, bibliography |
| Format | electronic resource, electronic resource, remote, 1 online resource (xvii, 133 leaves) : ill. (some col.) |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
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