本文關(guān)鍵詞： PEMFC 原位 XAFS 催化劑 結(jié)構(gòu)變化　出處：《中國科學院研究生院(上海應(yīng)用物理研究所)》2016年博士論文　論文類型：學位論文

【摘要】：質(zhì)子交換膜燃料電池(PEMFC)由于其構(gòu)造簡單,能量密度高,能量轉(zhuǎn)化效率高,環(huán)境友好等優(yōu)點,作為化學電源被廣泛的應(yīng)用。在氫-氧PEMFC中,氫陽極的反應(yīng)速率很快,陽極納米Pt/C催化劑具有很高的催化活性和穩(wěn)定性,氧陰極的反應(yīng)速率較慢,氧電極的電勢更負,因此如何提高燃料電池的陰極催化劑活性并且降低催化劑的成本,成為燃料電池的研究熱點之一。Pt具有催化活性高和穩(wěn)定性好是質(zhì)子交換膜燃料電池最常用的催化劑,但是Pt催化劑高昂的成本、較短的使用壽命極大地阻礙了其大規(guī)模的商業(yè)應(yīng)用。在Pt中摻雜非貴金屬元素如Fe、Co、N i等,有助于提高Pt催化劑的穩(wěn)定性和催化活性,同時也減少Pt的使用量,降低燃料電池的成本。但是在催化反應(yīng)過程中,Pt中摻雜的另外一種組分增強Pt的催化反應(yīng)機理尚不完全清楚�；谕捷椛涞腦射線吸收精細結(jié)構(gòu)(XAFS)方法具有元素特征選擇性,可以分別獲得燃料電池雙金屬納米催化劑中兩種金屬原子的局域幾何結(jié)構(gòu)和電子結(jié)構(gòu),同時該方法也適合研究原位條件下燃料電池催化劑的結(jié)構(gòu)變化,可以與透射電鏡(TEM)和X射線衍射(XRD)其它表征技術(shù)聯(lián)用,提供更豐富的結(jié)構(gòu)信息,包括價態(tài)、配位數(shù)、鍵長等。本文依托上海同步輻射裝置(SSRF),在BL14W1線站開展了燃料電池催化劑的原位XAFS方法研究,發(fā)展了燃料電池催化劑的原位XAFS實驗方法,同時結(jié)合一系列的非原位表征方法如TEM、XRD、XAFS等,系統(tǒng)的研究了Pt基雙金屬納米催化劑在催化反應(yīng)過程中的結(jié)構(gòu)變化,以及雙金屬組分在催化反應(yīng)過程中的相互作用關(guān)系。主要的研究內(nèi)容和結(jié)果如下:(1)依托上海光源X射線吸收精細結(jié)構(gòu)譜學線站B L14W1,建立并發(fā)展了用于氫-氧PEMFC原位XAFS實驗的測試裝置,以Pt/C納米催化劑作為PEMFC的陰極催化劑,Pd/C作為燃料電池的陽極催化劑,采集在工作狀態(tài)下的陰極催化劑的XAFS數(shù)據(jù),同步監(jiān)測燃料電池的C-V曲線和功率密度曲線,觀察到Pt/C催化劑在反應(yīng)過程中不同電位下氧化態(tài)的變化,在高電位下Pt/C催化劑的表面存在較強的Pt-O鍵,Pt-O鍵的存在降低了Pt/C催化氧化還原反應(yīng)(ORR)的活性,該研究同時也驗證了我們所建立的實驗裝置和研究方法的可行性和可靠性.(2)利用已經(jīng)建立的原位X AFS方法表征了三種商業(yè)燃料電池催化劑:HS-Pt/C,JM-Pt/C,JM-Pt Ru/C。隨著電壓的逐漸降低,HS-Pt/C和JM-Pt/C在催化反應(yīng)過程中都逐漸被還原,但是JM-Pt Ru/C在高電位時逐漸被還原,在低電位逐漸被氧化。影響催化活性的關(guān)鍵因素是零價態(tài)Pt的含量,Pt-O鍵的存在能夠抑制Pt/C催化劑的活性,Ru的存在沒有增強Pt催化ORR的活性,反而占據(jù)了Pt的催化劑活性中心,導致JM-Pt Ru/C催化劑的活性下降。(3)在Pt中摻雜過渡金屬元素C o形成的Pt C o/C雙金屬納米催化劑,與商業(yè)Pt/C催化劑相比,由于Co的存在能夠影響Pt的氧化程度,使得金屬Pt晶格變小,Pt-Pt鍵長縮短,導致Pt Co/C具有更小的納米尺寸,減小了Pt-Pt鍵之間的距離,從而提高Pt Co/C納米催化劑中Pt的催化活性。過渡金屬Co有比Pt更多的d帶空位,原位XAFS實驗揭示了Pt Co/C在催化反應(yīng)過程中Pt的d電子向過渡金屬Co的轉(zhuǎn)移過程,Pt的d帶空位的增加,有利于提高Pt催化O RR反應(yīng)的性能。綜上所述,本文依托上海光源X射線吸收譜學線站BL14W1搭建了原位燃料電池催化劑實驗測試裝置,優(yōu)化了實驗條件,實現(xiàn)了在線XAFS數(shù)據(jù)的采集。建立了包括測試裝置的研制搭建、測試技術(shù)的優(yōu)化、在線數(shù)據(jù)的采集分析在內(nèi)的用于PEMFC催化劑結(jié)構(gòu)研究的一套原位XAFS實驗方法,為國內(nèi)相關(guān)研究領(lǐng)域的科研人員利用上海光源開展燃料電池原位XAFS研究提供了新的方法。
[Abstract]:Proton exchange membrane fuel cell (PEMFC) because of its simple structure, high energy density, high energy conversion efficiency, environment friendly and other advantages, is widely used as chemical power. In hydrogen oxygen PEMFC, the reaction rate of hydrogen anode quickly, anode nano Pt/C catalyst has high catalytic activity and stability, reaction the rate of oxygen, the oxygen electrode potential is more negative, so how to improve the fuel cell cathode catalyst activity and reduce the cost of the catalyst, the fuel cell become one of research hotspots of.Pt has a high catalytic activity and stability are good catalysts for proton exchange membrane fuel cell is the most commonly used, but the Pt catalyst is high cost, short the service life greatly hindered the large-scale commercial applications. Doping in Pt non noble metal elements such as Fe, Co, N, I etc., is helpful to improve the stability and catalytic activity of Pt catalyst, at the same time Also reduce the amount of use of Pt, reduce the cost of fuel cells. But during the catalytic reaction of Pt doped in another component to enhance the catalytic reaction mechanism of Pt is still not entirely clear. The synchrotron radiation X ray absorption fine structure (XAFS) method is selected based on element characteristics, can obtain geometric local structure and the electronic structure of two kinds of fuel cell Nanobimetallic catalyst in metal atoms respectively at the same time, this method is also suitable for changes in the structure of fuel cell catalyst of in situ conditions, and transmission electron microscopy (TEM) and X ray diffraction (XRD) combined with other characterization techniques, provide more structure information, including the valence states. The coordination number and bond length. This paper is based on the Shanghai synchrotron radiation facility (SSRF), the station carried out research on the method of in situ XAFS fuel cell catalyst in the BL14W1 line, the development of in situ XAFS experimental method of fuel cell catalyst, At the same time, combined with a series of in situ characterization methods such as TEM, XRD, XAFS, and systematic study of the structural change of Pt based bimetallic catalysts in the catalytic reaction in the process of interaction between the two metal components and the catalytic reaction process. The main research contents and results are as follows: (1) based on the Shanghai light source X ray absorption fine structure spectrum line station B L14W1, set up and test device for hydrogen oxygen PEMFC in situ XAFS experimental development, with nanometer Pt/C as cathode catalyst PEMFC, Pd/C as the anode catalyst of fuel cell, XAFS data collection of cathode catalyst in the working condition, the synchronous monitoring of fuel the battery of C-V curve and power density curve, observed changes in oxidation state under different potentials of Pt/C catalyst in the reaction process, the high potential surface of Pt/C catalyst has strong Pt-O bonds, Pt-O bonds are falling Low Pt/C catalytic oxidation reduction reaction (ORR) activity, the study also verified the feasibility and reliability of experimental apparatus and research method established by us. (2) by in situ X AFS method has been established to characterize three kinds of commercial fuel cell catalyst: HS-Pt/C, JM-Pt/C, JM-Pt, Ru/C. gradually decreases with voltage HS-Pt/C, and JM-Pt/C in the catalytic reaction process was gradually reduced, but the JM-Pt Ru/C was gradually reduced in high potential, low potential is gradually oxidized. The key factors affecting the catalytic activity of the content is zero valence state of Pt, the presence of Pt-O bonds can inhibit the activity of Pt/C catalyst, Ru had no obvious enhancement of Pt catalyst the activity of ORR, but occupy the active centers of the catalyst Pt, resulting in a decline in the activity of the catalyst. JM-Pt Ru/C (3) Pt C o/C bimetallic catalyst for the formation of doping transition metal element C o in Pt, and commercial Pt/C Compared with the catalyst, due to the presence of Co can affect the degree of oxidation of Pt, makes the metal lattice Pt Pt-Pt smaller, shorten the bond length, resulting in Pt Co/C has a smaller nano size and reduced the Pt-Pt distance between the keys, so as to improve the catalytic activity of Pt catalyst in Co/C nano Pt. There are more than Pt d with vacancy transition metal Co, XAFS in situ experiments revealed that Pt Co/C during the catalytic reaction of Pt d to the electronic transfer process of transition metal Co, D increased with Pt vacancy, is beneficial to improve the catalytic performance of Pt O RR reaction. In summary, this paper relies on the Shanghai light source X ray absorption spectroscopy in situ fuel line station BL14W1 the battery test device of catalyst structures, the experimental conditions were optimized to achieve online XAFS data acquisition was established. The development includes the testing device structures, optimization test technology, PEMFC catalyst for online data acquisition and analysis, A set of in-situ XAFS experimental methods for structural research, which provides a new method for researchers in the field of domestic research, using Shanghai light source to carry out in situ XAFS research of fuel cell.

【學位授予單位】：中國科學院研究生院(上海應(yīng)用物理研究所)
【學位級別】：博士
【學位授予年份】：2016
【分類號】：O643.36;TM911.4

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