本文選題：貴金屬納米催化劑　切入點：高指數(shù)晶面　出處：《吉林大學》2017年博士論文

【摘要】：全球人口不斷增加,能源需求日益擴大,氣候變化和環(huán)境問題日趨嚴重,如何保護我們賴以生存的地球家園,可謂是迫在眉睫!催化降解污染物、發(fā)展可持續(xù)清潔能源是解決上述問題的有效手段。燃料電池及氫能源是目前最具應用前景的清潔能源,但無論是催化降解污染物,還是發(fā)展燃料電池或氫能源都需要高效的催化劑。因此,如何提高催化劑的催化性能和節(jié)約應用成本是技術應用的核心問題。也就是說設計優(yōu)化催化劑的組成成分、納米結構、形貌、裸露晶面及大小尺寸是提高催化劑催化性能的關鍵所在。金Au、銀Ag貴金屬納米催化劑,具有生物相容性、穩(wěn)定性,是常用高效、持久的催化劑,在催化降解有機污染物、汽車尾氣處理及CO2催化還原應用中都取得了出色的效果。大量的實驗證明,催化劑裸露的表面晶面直接影響著催化劑的催化反應速率及激活勢壘。高指數(shù)晶面,相對于低指數(shù)的基礎晶面,存有大量的臺階面、晶體缺陷及豐富的低配位原子,具有更好的催化活性。本文重點發(fā)展簡單、綠色、經(jīng)濟的水相合成方式,通過選擇不同的還原劑、調(diào)控溶液的p H環(huán)境、控制反應動力學、可控設計合成出富有高指數(shù)晶面的多孔Au、Ag納米結構及多面體,優(yōu)化并提升催化降解有機污染物(p-硝基苯酚等)、葡萄糖燃料電池及電解水析氫性能,揭示貴金屬納米催化劑的形貌、尺寸、結構與催化性能的構效關系。開展了如下的研究內(nèi)容:1.多孔Ag的可控制備及其催化性能研究。我們實現(xiàn)了對多孔Ag納米晶的形貌、尺寸、結晶性及孔徑分布的可控制備,并優(yōu)化提升了其催化性能。多孔Ag催化性能的優(yōu)化主要是通過調(diào)控以下參數(shù)實現(xiàn)的:多孔Ag的比表面積及在多孔結構表面的臺階steps、突起ledges和缺陷kinks處的Ag原子數(shù)目。這部分工作,我們主要是發(fā)展了一種簡單的兩步法合成體系。通過調(diào)節(jié)溶液的p H環(huán)境來調(diào)控多孔Ag的形貌及尺寸(形貌可實現(xiàn)梭形及四邊形的可控合成,尺寸可實現(xiàn)2.5mm到36mm的調(diào)控);通過調(diào)節(jié)熱處理的溫度、升溫速率、加熱時間調(diào)控多孔Ag納米晶的結晶性、表面缺陷及孔徑分布。隨后,在p-硝基苯酚等有機污染物催化降解應用中,我們探究了多孔Ag的形貌與性能的構效關系。研究結果表明:多孔Ag在催化降解有機污染物時表現(xiàn)出優(yōu)異的催化活性。其中,4mm的四邊形多孔Ag的催化活性最好,其反應速率可達到6.43*10-2 s-1,并且在多次循環(huán)利用后仍保持較高的催化活性。多孔Ag的高催化活性主要歸結于:規(guī)則形貌(梭形或者四邊形)、多孔結構、高比表面積、優(yōu)異的滲透性、離子遷移率以及豐富的高指數(shù)晶面等高活性位點。鑒于多孔Ag上述的結構優(yōu)勢,相信其在電化學催化、傳感和驅動器等實際應用中存在潛在的應用前景。2.多孔Au的可控制備及其GOR催化性能研究。我們創(chuàng)造性地發(fā)展了低溫動力學方式,成功合成出多孔Au納米結構。此合成方法突破了經(jīng)典圖爾克維奇(Turkevich)利用檸檬酸鈉熱還原氯金酸制備Au的方式。其中,低溫合成條件改變了檸檬酸根在Au表面的吸附方式,獲得表面“清潔”的多孔Au納米晶�；诙嗫譇u的結構特點,我們探究了其表面結構與催化性能的關系。研究表明,表面“清潔”的多孔Au在葡萄糖電催化氧化中取得出色的催化效果,其催化氧化電流密度可高達9 A cm-2 g-1,是Turkevich-Au(0.45 A cm-2g-1)的20倍,也是當前所報道的最優(yōu)值(2.65 A cm-2g-1)的3.4倍。多孔Au的高催化性能,主要歸結于以下兩方面:1)多孔Au具有清潔的表面、能夠自由傳輸電子、最大化地暴露其活性位點;2)多孔Au具有大的電化學比表面積、多孔結構、良好的離子遷移率、豐富的高指能面及原子臺階位steps等高活性位點。高性能多孔Au在葡萄糖電催化氧化中的成功應用,為葡萄糖燃料電池在未來生活中的實際應用提供了廣闊的商業(yè)應用前景。3.可控制備二十面體Au及其HER性能研究。我們繼續(xù)發(fā)展了低溫動力學的方式,成功制備出表面“清潔”的多重孿晶二十面體Au。同時,通過調(diào)控反應時間,設計合成出截角二十面體Au。(截角)二十面體Au具有豐富的孿晶界及邊角原子等高活性位點。將二十面體Au應用到電解水HER催化反應中,我們發(fā)現(xiàn)隨著測試循環(huán)次數(shù)的增加,二十面體Au的催化活性隨之增加(過電位、Tafel斜率、電阻都隨之降低)。30 000次循環(huán)后,二十面體Au的催化活性基本可以和商業(yè)Pt-C相媲美。初步的研究結果表明:催化劑的晶體缺陷能夠顯著增強其催化活性,多重孿晶中存在可調(diào)的應力應變;外加電位提供外部動力壓縮了Au的晶格參數(shù)、使d帶電子上移、優(yōu)化了Au-H鍵能、提高了電解水HER性能。
[Abstract]:Increasing of global population, energy demand is growing, climate change and environmental problems become increasingly serious, how to protect the survival of our planet, it is imminent! The catalytic degradation of pollutants, the sustainable development of clean energy is an effective means to solve the above problems. The fuel cell and hydrogen energy is the most promising clean energy, but no matter is the catalytic degradation of pollutants, or the development of fuel cells and hydrogen energy need efficient catalyst. Therefore, how to improve the performance of the catalyst and save the application cost is a key problem in technology application. That is to say design optimization of composition, catalyst of nano structure, morphology, size and size of bare crystal surface is the key to improve the catalytic performance the catalyst. Au gold and silver Ag noble metal nano catalyst, biocompatibility, stability, is efficient, durable catalyst, In the photocatalytic degradation of organic pollutants and applications have achieved excellent results processing and automobile exhaust catalytic reduction of CO2. A large number of experiments show that the catalyst surface crystal exposed directly affects the catalytic reaction rate of the catalyst and the activation barrier. High index surfaces, relative to the low number of basic crystal surface, there are a lot of stepped surface and the crystal defects and rich low coordination atoms, has better catalytic activity. This paper focuses on the development of simple, green, aqueous synthesis economy, by choosing a different reducing agent, control solution P H environment control, reaction kinetics, controllable synthesis of rich design of high index surfaces of porous Au nanostructures, Ag and the polyhedron, and enhance the optimization of catalytic degradation of organic pollutants (p- nitro phenol), glucose fuel cell and water electrolysis hydrogen evolution performance, reveal the morphology of noble metal nano catalyst size, structure and catalytic The structure-activity relationship of performance. The research contents are as follows: 1. porous Ag can be prepared and their catalytic properties. We realize the control of morphology, porous Ag nano crystal size, crystallinity and pore size distribution can be controlled, and optimized to enhance the catalytic performance of porous Ag. Optimization of catalytic properties of the main the regulation is realized by the following parameters: the porous surface area of Ag and steps on the steps of porous structure on the surface, the number of Ag atoms ledges and kinks processes. This defect is the main part of the work, we developed a simple two step synthesis system. By adjusting the P of the solution to control the morphology and size of H porous Ag (controlled synthesis, morphology can be fusiform and quadrilateral size can achieve 2.5mm to 36mm control); by adjusting the heat treatment temperature, heating rate, heating time regulation of crystalline porous nanocrystalline Ag, and surface defects The pore size distribution in p-. Subsequently, p-nitrophenol catalytic degradation of organic pollutants such as application, we explore the structure-activity relationship of the morphology and properties of porous Ag. The results showed that the porous Ag exhibits excellent catalytic activity in the catalytic degradation of organic pollutants. The best catalytic activity of the porous Ag quadrilateral 4mm, the the reaction rate of 6.43*10-2 can reach s-1, and still maintain high catalytic activity in the repeated recycling. High catalytic activity of porous Ag is mainly due to the rules of morphology (fusiform or quadrilateral), porous structure, high surface area, excellent permeability, ion mobility and rich high index surfaces etc. high active site. In view of the advantages of porous structure of Ag, believes in electrochemical catalysis, applications of porous.2. Au potential practical application of sensor and driver in the preparation of catalytic performance and GOR control. We creatively developed low-temperature dynamics, the successful synthesis of Au nano porous structure. This method breaks through the classical Turk Vecchi (Turkevich) using sodium citrate reduction of HAuCl4 Au preparation method. The synthesis conditions of low temperature change of citrate adsorption on the Au surface, porous nanocrystalline Au surface "clean". Based on the structure characteristics of porous Au, we explore the relationship between the surface structure and catalytic performance. The results show that the porous Au surface cleaning has excellent catalytic effect on glucose oxidation, the oxidation current density can be as high as 9 A cm-2 g-1, Turkevich-Au (0.45 A cm-2g-1) 20 times, but also the optimal reported value (2.65 A cm-2g-1) 3.4 times. The high catalytic performance of porous Au, mainly due to the following two aspects: 1) porous Au have a clean surface, can be free The electronic transmission, to maximize the exposure of the active site; 2) porous Au has large electrochemical specific surface area, porous structure, good ion mobility, which can rich the surface and high atomic steps steps active site. The successful application of high performance porous Au in glucose oxidation of glucose the fuel cell in the future practical application in life provides the business prospects of.3. can be prepared in twenty face Au and HER properties of the control. We continue to develop the low temperature dynamics, the prepared multiple twin surface cleaning of twenty sides of Au. at the same time, by adjusting the reaction time, the design and synthesis of a truncated Au. (truncated) twenty face twenty face body Au has twin boundaries and high angle edge rich atom active site. The Au is applied to the twenty surface water electrolysis reaction catalyzed by HER, we found that with the number of test cycles Increase the catalytic activity of twenty surface Au increased (overpotential, Tafel slope, resistance decreased.30) after 000 cycles, the catalytic activity of twenty surface Au can be comparable to Pt-C and business. The preliminary results show that the crystal defects of catalyst can significantly enhance the catalytic activity, stress and strain adjustable multiple twins; applied potential provides external power compression of the lattice parameters of Au, with d electronic shift, optimize the Au-H bond energy, improve the performance of HER water electrolysis.

【學位授予單位】：吉林大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：O643.36

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