新能源材料結(jié)構(gòu)和性能的同步輻射研究
發(fā)布時(shí)間：2019-03-10 21:24
【摘要】：隨著全球經(jīng)濟(jì)和技術(shù)的快速發(fā)展,能源和環(huán)境已然成為國(guó)際社會(huì)面臨最為嚴(yán)峻的兩大基本問(wèn)題。優(yōu)化能源結(jié)構(gòu),發(fā)展高效的低碳清潔新能源是當(dāng)今世界可持續(xù)發(fā)展的重要方向和途徑。新能源材料作為新能源開發(fā)利用的關(guān)鍵,目前仍然處于蓄力發(fā)展階段,還存在有轉(zhuǎn)換效率低、能量密度低以及成本高等諸多問(wèn)題。進(jìn)一步拓展新能源材料的種類,選擇合適的模型材料體系研究它們的結(jié)構(gòu)、組成、性能之間的關(guān)系,對(duì)提升新能源生產(chǎn)利用水平以及實(shí)現(xiàn)其廣泛應(yīng)用都具有重要意義。本論文通過(guò)設(shè)計(jì)合成單原子催化劑和原子層厚度超薄納米片作為研究高效新能源材料的切入點(diǎn),明確其結(jié)構(gòu)和性能之間的關(guān)系,旨在為優(yōu)化設(shè)計(jì)新能源材料提供新的認(rèn)識(shí)和思路。首先合成單活性位點(diǎn)鈷/氮化碳光催化劑,實(shí)現(xiàn)高效、自發(fā)的太陽(yáng)光驅(qū)動(dòng)全解水產(chǎn)氫,并揭示其內(nèi)在機(jī)制在于能有效地分離光生電子-空穴對(duì)。其次制備出原子層厚度金屬錫超薄納米片用于高效電催化還原二氧化碳,結(jié)合同步輻射X射線吸收精細(xì)結(jié)構(gòu)譜學(xué)(XAFS)和電化學(xué)表征揭示其表面配位不飽和結(jié)構(gòu)是有效穩(wěn)定CO_2還原中間體CO_2-的關(guān)鍵。我們還利用原位XAFS實(shí)驗(yàn)技術(shù)揭示了 lcFe-Pt/SiO_2催化劑中Fe的單原子結(jié)構(gòu),深入研究了其對(duì)一氧化碳選擇性氧化(PROX)催化反應(yīng)的高活性機(jī)理。本論文的具體研究?jī)?nèi)容如下:1、單原子鈷/氮化碳的光催化全解水研究光解水過(guò)程包含著復(fù)雜的多電子、多步驟反應(yīng),對(duì)催化劑材料的要求非常高,目前大多數(shù)光催化劑在沒(méi)有犧牲劑的情況下很難實(shí)現(xiàn)全解水。本論文通過(guò)精確設(shè)計(jì)和構(gòu)建一種單活性位點(diǎn)的鈷/氮化碳光催化劑,來(lái)分離光生電子和空穴對(duì),實(shí)現(xiàn)高效的全解水性能。利用氮化碳材料的空間限域效應(yīng)合成原子級(jí)分散的復(fù)合結(jié)構(gòu),同步輻射XAFS和高角環(huán)形暗場(chǎng)像(HAADF-STEM)明確它形成了單位點(diǎn)的Co1-P4原子結(jié)構(gòu),紫外可見(jiàn)漫反射光譜(UV-visDRS)和同步輻射光電子能譜(SRPES)表征結(jié)果證實(shí)該復(fù)合結(jié)構(gòu)在電子能帶結(jié)構(gòu)中形成了特殊中間態(tài),它不僅極大地提高了材料的可見(jiàn)光吸收,而且能有效抑制光生電子-空穴對(duì)復(fù)合,成功將光生載流子壽命提高了約20倍。該光催化劑在模擬太陽(yáng)光照、不加犧牲劑和貴金屬的條件下全解水產(chǎn)氫速率達(dá)410.3 μmol h~(-1) g~(-1),其中500 nm波長(zhǎng)處量子效率達(dá)到2.2 %。2、原子層厚度錫納米片的電還原二氧化碳研究超薄納米片材料因?yàn)樘厥獾亩S電子限域效應(yīng),具有一系列特殊的物理和化學(xué)屬性。本論文設(shè)計(jì)和制備出石墨烯限域二維Sn納米片的類三明治結(jié)構(gòu),厚度僅為1.4nm。將其作為電催化劑還原CO_2,在~(-1).8Vvs.SCE (飽和甘汞電極)的電極電勢(shì)條件下,電流密度達(dá)到21.1 mA cm-2,分別是Sn塊材,15 nm Sn顆粒以及15nmSn顆粒/石墨烯物理混合物的13、2.5和2倍。通過(guò)對(duì)SnK邊XAFS譜的分析和計(jì)算表明,Sn納米片中Sn的近鄰配位相比于Sn塊材和納米顆粒明顯降低,存在明顯的不飽和配位,最近鄰Sn-Sn配位數(shù)從2.0和4.0分別減小為1.4和2.7。電化學(xué)測(cè)試進(jìn)一步揭示該不飽和配位可以有效穩(wěn)定CO_2還原中間體CO_2-,這為設(shè)計(jì)高效CO_2還原電催化劑提供了重要的實(shí)驗(yàn)依據(jù)。3、單原子Fe1-Pt/SiO_2的一氧化碳選擇性氧化(PROX)研究原位XAFS技術(shù)是研究催化反應(yīng)過(guò)程中動(dòng)態(tài)催化劑結(jié)構(gòu)變化的一種非常重要的方法,但通常情況下,它給出的是催化體系中所有吸收原子周圍局域結(jié)構(gòu)排布的平均信息,選擇性分離獲取催化劑表界面活性中心結(jié)構(gòu)仍然面臨著極大挑戰(zhàn)。單原子催化劑在表現(xiàn)出高活性的同時(shí)還具有均一分散的催化活性位點(diǎn),為原位XAFS研究結(jié)構(gòu)和性能關(guān)系提供了簡(jiǎn)化的理想模型。本論文利用原子層沉積技術(shù)精確制備了 1 cFe-Pt/SiO_2單原子催化劑用于PROX反應(yīng),在198-380 K溫度區(qū)間實(shí)現(xiàn)了 CO氧化的100%的選擇性和轉(zhuǎn)化率轉(zhuǎn)化。基于原位同步輻射XAFS技術(shù)監(jiān)測(cè)到在室溫H2條件下1cFe-Pt/SiO_2中的Fe3+就可以被還原為Fe2+,并明確不同價(jià)態(tài)的Fe離子都主要以單原子形式存在。同時(shí)首次觀察到在PROX反應(yīng)條件下的活性位點(diǎn)是原子級(jí)分散的Pt-Fe1(OH)3物種,結(jié)合密度泛函理論計(jì)算進(jìn)一步證實(shí)正是該結(jié)構(gòu)導(dǎo)致了 1cFe-Pt/SiO_2單原子催化劑的高效PROX催化活性。
[Abstract]:With the rapid development of global economy and technology, energy and environment have become the two most serious problems facing the international community. Optimizing the energy structure and developing high-efficiency and low-carbon clean new energy is the important direction and way of the sustainable development in the world today. As the key to the new energy development and utilization, new energy materials are still in the development stage of energy storage, and there are many problems such as low conversion efficiency, low energy density and high cost. It is of great significance to further expand the kinds of new energy materials, to select the appropriate model material system to study their structure, composition and performance, and to improve the utilization level of new energy production and to realize its wide application. This paper, through the design and synthesis of single-atom catalyst and atomic layer thickness ultrathin nanosheet, is a breakthrough point for the study of high-efficiency new energy materials, and the relationship between its structure and performance is defined, and the aim of this paper is to provide a new understanding and thinking for the optimization of new energy materials. Firstly, a single active site cobalt/ carbon nitride photocatalyst is synthesized, so that high-efficiency and spontaneous sunlight driving is realized to fully solve the hydrogen, and the mechanism is that the photo-generated electron-hole pair can be effectively separated. X-ray absorption fine-structure spectroscopy (XAFS) and electrochemical characterization of the atomic layer are the key to the effective and stable CO _ 2 reduction of the intermediate CO _ 2. The monoatomic structure of Fe in the lcFe-Pt/ SiO _ 2 catalyst was also revealed by in-situ XAFS experiment, and the high activity mechanism of the catalytic reaction of the selective oxidation of carbon monoxide (PROX) was studied. The specific research contents of this thesis are as follows:1. The photodegradation water process of a single-atom-cobalt/ carbon-nitride-based photocatalytic water-photolysis process comprises a complex multi-electron and multi-step reaction, and the requirement on the catalyst material is very high. At present, most of the photocatalysts are difficult to achieve full solution without the agent. In this paper, through the precise design and construction of a single active site cobalt/ carbon nitride photocatalyst, the photo-generated electron and hole pairs are separated, and the high-efficiency full-solution water performance is realized. The composite structure, synchrotron radiation XAFS and high-angle annular dark field image (HAADF-STEM) of the carbon nitride material are used to synthesize the atomic-grade dispersed composite structure, and the Co1-P4 atomic structure of the unit point is defined by the synchrotron radiation XAFS and the high-angle annular dark field image (HAADF-STEM). The results of UV-visDRS and SRPES show that the composite structure forms a special intermediate state in the electron energy band structure, which not only greatly improves the visible light absorption of the material, but also can effectively inhibit the recombination of the photo-generated electron-hole pair, The success of the photo-generated carrier lifetime is increased by about 20 times. The photocatalyst has the full solution of the hydrogen rate of 410.3. mu. mol h to (-1) g-(-1) under the condition of simulating the sun light, without the addition of a condensing agent and a noble metal, wherein the quantum efficiency at the wavelength of 500 nm is 2.2%. The electroreducing carbon dioxide of the atomic layer thickness tin nanosheet has a series of special physical and chemical properties due to the special two-dimensional electron confinement effect. In this paper, the sandwich structure of the two-dimensional Sn nano-sheet of the graphene-limited domain is designed and prepared, and the thickness is only 1.4 nm. The current density was 21.1 mA cm-2 under the electrode potential of ~ (-1).8 V vs. SCE (saturated calomel electrode) as an electrocatalyst, and 13, 2.5 and 2 times of the physical mixture of Sn block,15 nm Sn particles and 15 nm Sn particles/ graphene, respectively. The analysis and calculation of the SnK-side XAFS spectrum show that the near-nearest-neighbor coordination of Sn in the Sn nano-sheet is obviously lower than that of the Sn-block material and the nano-particles, and has obvious unsaturated coordination, and the nearest neighbor Sn-Sn coordination number is reduced from 2.0 and 4.0 to 1.4 and 2.7, respectively. The electrochemical test further reveals that the unsaturated coordination can effectively and stably stabilize the CO _ 2-, which provides an important experimental basis for the design of a high-efficiency CO _ 2 reduction electric catalyst. In-situ XAFS technology is a very important method to study the change of dynamic catalyst structure in the process of catalytic reaction, but in general, It gives the average information of the local structure arrangement of all the absorption atoms in the catalytic system, and the selective separation and acquisition of the active center structure of the catalyst table still faces great challenges. The monoatomic catalyst also has a uniform dispersed catalytic activity site while exhibiting high activity, and provides a simplified ideal model for the in-situ XAFS study structure and performance relationship. In this paper,1 cFe-Pt/ SiO _ 2 monoatomic catalyst is prepared by atomic layer deposition technique for PROX reaction, and the selectivity and conversion rate of 100% of CO oxidation are realized in the temperature range of 198-380 K. Based on the in-situ synchrotron radiation XAFS technique, the Fe ~ (3 +) in 1 cFe-Pt/ SiO _ 2 at room temperature (H2) can be reduced to Fe 2 +, and the Fe ions in different valence states are mainly present in single atom form. At the same time, it was first observed that the active site under the condition of PROX was an atomic-grade dispersed Pt-Fe1 (OH)3 species, and in combination with the density functional theory, it was further confirmed that this structure resulted in the high-efficiency PROX catalytic activity of the 1 cFe-Pt/ SiO _ 2 monoatomic catalyst.
【學(xué)位授予單位】：中國(guó)科學(xué)技術(shù)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：TB303
本文編號(hào)：2438040
[Abstract]:With the rapid development of global economy and technology, energy and environment have become the two most serious problems facing the international community. Optimizing the energy structure and developing high-efficiency and low-carbon clean new energy is the important direction and way of the sustainable development in the world today. As the key to the new energy development and utilization, new energy materials are still in the development stage of energy storage, and there are many problems such as low conversion efficiency, low energy density and high cost. It is of great significance to further expand the kinds of new energy materials, to select the appropriate model material system to study their structure, composition and performance, and to improve the utilization level of new energy production and to realize its wide application. This paper, through the design and synthesis of single-atom catalyst and atomic layer thickness ultrathin nanosheet, is a breakthrough point for the study of high-efficiency new energy materials, and the relationship between its structure and performance is defined, and the aim of this paper is to provide a new understanding and thinking for the optimization of new energy materials. Firstly, a single active site cobalt/ carbon nitride photocatalyst is synthesized, so that high-efficiency and spontaneous sunlight driving is realized to fully solve the hydrogen, and the mechanism is that the photo-generated electron-hole pair can be effectively separated. X-ray absorption fine-structure spectroscopy (XAFS) and electrochemical characterization of the atomic layer are the key to the effective and stable CO _ 2 reduction of the intermediate CO _ 2. The monoatomic structure of Fe in the lcFe-Pt/ SiO _ 2 catalyst was also revealed by in-situ XAFS experiment, and the high activity mechanism of the catalytic reaction of the selective oxidation of carbon monoxide (PROX) was studied. The specific research contents of this thesis are as follows:1. The photodegradation water process of a single-atom-cobalt/ carbon-nitride-based photocatalytic water-photolysis process comprises a complex multi-electron and multi-step reaction, and the requirement on the catalyst material is very high. At present, most of the photocatalysts are difficult to achieve full solution without the agent. In this paper, through the precise design and construction of a single active site cobalt/ carbon nitride photocatalyst, the photo-generated electron and hole pairs are separated, and the high-efficiency full-solution water performance is realized. The composite structure, synchrotron radiation XAFS and high-angle annular dark field image (HAADF-STEM) of the carbon nitride material are used to synthesize the atomic-grade dispersed composite structure, and the Co1-P4 atomic structure of the unit point is defined by the synchrotron radiation XAFS and the high-angle annular dark field image (HAADF-STEM). The results of UV-visDRS and SRPES show that the composite structure forms a special intermediate state in the electron energy band structure, which not only greatly improves the visible light absorption of the material, but also can effectively inhibit the recombination of the photo-generated electron-hole pair, The success of the photo-generated carrier lifetime is increased by about 20 times. The photocatalyst has the full solution of the hydrogen rate of 410.3. mu. mol h to (-1) g-(-1) under the condition of simulating the sun light, without the addition of a condensing agent and a noble metal, wherein the quantum efficiency at the wavelength of 500 nm is 2.2%. The electroreducing carbon dioxide of the atomic layer thickness tin nanosheet has a series of special physical and chemical properties due to the special two-dimensional electron confinement effect. In this paper, the sandwich structure of the two-dimensional Sn nano-sheet of the graphene-limited domain is designed and prepared, and the thickness is only 1.4 nm. The current density was 21.1 mA cm-2 under the electrode potential of ~ (-1).8 V vs. SCE (saturated calomel electrode) as an electrocatalyst, and 13, 2.5 and 2 times of the physical mixture of Sn block,15 nm Sn particles and 15 nm Sn particles/ graphene, respectively. The analysis and calculation of the SnK-side XAFS spectrum show that the near-nearest-neighbor coordination of Sn in the Sn nano-sheet is obviously lower than that of the Sn-block material and the nano-particles, and has obvious unsaturated coordination, and the nearest neighbor Sn-Sn coordination number is reduced from 2.0 and 4.0 to 1.4 and 2.7, respectively. The electrochemical test further reveals that the unsaturated coordination can effectively and stably stabilize the CO _ 2-, which provides an important experimental basis for the design of a high-efficiency CO _ 2 reduction electric catalyst. In-situ XAFS technology is a very important method to study the change of dynamic catalyst structure in the process of catalytic reaction, but in general, It gives the average information of the local structure arrangement of all the absorption atoms in the catalytic system, and the selective separation and acquisition of the active center structure of the catalyst table still faces great challenges. The monoatomic catalyst also has a uniform dispersed catalytic activity site while exhibiting high activity, and provides a simplified ideal model for the in-situ XAFS study structure and performance relationship. In this paper,1 cFe-Pt/ SiO _ 2 monoatomic catalyst is prepared by atomic layer deposition technique for PROX reaction, and the selectivity and conversion rate of 100% of CO oxidation are realized in the temperature range of 198-380 K. Based on the in-situ synchrotron radiation XAFS technique, the Fe ~ (3 +) in 1 cFe-Pt/ SiO _ 2 at room temperature (H2) can be reduced to Fe 2 +, and the Fe ions in different valence states are mainly present in single atom form. At the same time, it was first observed that the active site under the condition of PROX was an atomic-grade dispersed Pt-Fe1 (OH)3 species, and in combination with the density functional theory, it was further confirmed that this structure resulted in the high-efficiency PROX catalytic activity of the 1 cFe-Pt/ SiO _ 2 monoatomic catalyst.
【學(xué)位授予單位】：中國(guó)科學(xué)技術(shù)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：TB303
【參考文獻(xiàn)】
相關(guān)期刊論文 前1條
1 韋世強(qiáng);孫治湖;潘志云;閆文盛;鐘文杰;賀博;謝治;韋正;;XAFS在凝聚態(tài)物質(zhì)研究中的應(yīng)用[J];中國(guó)科學(xué)技術(shù)大學(xué)學(xué)報(bào);2007年Z1期
相關(guān)博士學(xué)位論文 前1條
1 儲(chǔ)旺盛;T-EXAFS研究過(guò)渡金屬二硼化物的晶格動(dòng)力學(xué)行為及其同位素效應(yīng)[D];中國(guó)科學(xué)技術(shù)大學(xué);2007年
，本文編號(hào)：2438040
本文鏈接：http://sikaile.net/kejilunwen/cailiaohuaxuelunwen/2438040.html
最近更新
教材專著
