【摘要】：直接甲醇燃料電池最常用的陽極催化材料是Pt,從近些年的國內(nèi)外研究成果來看,Pt的優(yōu)越催化性能目前還難以被其它普通金屬所替代。但是,Pt催化劑存在的問題也顯而易見。Pt不但價(jià)格昂貴而且容易被甲醇氧化過程產(chǎn)生的類CO中間體所毒化,致使其催化活性和穩(wěn)定性降低。為了降低催化劑的成本,提高Pt催化劑的催化活性和抗CO中毒能力,本工作采用向Pt催化劑中添加第二種組分/助劑(金屬或金屬氧化物)的方法,利用助劑與Pt之間的電子效應(yīng)、協(xié)同效應(yīng)等調(diào)變Pt的表面結(jié)構(gòu)性質(zhì),進(jìn)而調(diào)變其抗CO中毒能力和催化性能(活性、穩(wěn)定性)。具體結(jié)果如下:1.以石墨烯為載體,通過液相中共還原的方法,制備了一系列具有不同原子比的負(fù)載型非合金雙金屬催化劑PtmAu/RGO(m代表Pt/Au原子比,m=0.5~2.0),考察了不同摩爾比的助劑Au對(duì)Pt催化劑在堿性電解質(zhì)中催化氧化甲醇的助催化作用。利用掃描電子顯微鏡(SEM)、透射電子顯微鏡(TEM)、X射線衍射(XRD)、X射線光電子能譜(XPS)等技術(shù)對(duì)催化劑的形貌、晶體結(jié)構(gòu)和電子結(jié)構(gòu)進(jìn)行了表征,利用電化學(xué)測(cè)試技術(shù)如循環(huán)伏安法和計(jì)時(shí)電流法對(duì)催化劑進(jìn)行了催化性能的測(cè)試。研究結(jié)果顯示,助劑Au的加入可顯著提高Pt催化劑在堿性介質(zhì)中抗CO中毒能力和對(duì)甲醇氧化的電催化性能。Pt催化劑上CO中毒程度的降低與催化劑表面CO生成程度降低而不是CO分子的快速脫除有關(guān)。系列PtmAu/RGO催化劑的催化性能與催化劑的m值具有火山型關(guān)系,在本實(shí)驗(yàn)研究范圍內(nèi),當(dāng)Pt/Au原子比為1.0時(shí),催化劑具有最高的電催化活性和電化學(xué)穩(wěn)定性。Pt1.0Au/RGO催化劑樣品的起始電位最負(fù)(-0.78 V),與Pt/RGO(-0.64 V)相比,電位負(fù)移140 mV左右;其峰電流最高(0.81 A mg-1Pt+Au),分別是Pt/RGO(0.30 A mg-1Pt+Au)、Pt0.5Au/RGO(0.50 A mg-1Pt+Au)、Pt0.8Au/RGO(0.70 A mg-1Pt+Au)及Pt2.0Au/RGO(0.41 A mg-1Pt+Au)催化劑樣品的2.70、1.62、1.15和1.97倍。2.利用簡(jiǎn)單的化學(xué)沉淀法合成了納米片、珊瑚狀及納米棒狀的納米二氧化錳,并將其作為助劑/載體添加至Pt催化劑中,制備了三種Pt/MnO_2催化劑,分別記作Pt/MnO_2-P、Pt/MnO_2-C和Pt/MnO_2-R,研究了不同形貌的MnO_2載體對(duì)Pt催化性能的影響。通過SEM、TEM、XRD等對(duì)樣品進(jìn)行了物理化學(xué)性質(zhì)表征,并在酸性電解質(zhì)中,研究了催化劑對(duì)甲醇電催化氧化的性能。結(jié)果表明,不同形貌的二氧化錳載體與Pt顆粒間的相互作用不同,對(duì)甲醇氧化反應(yīng)的助催化作用也不一樣。在CO剝離伏安曲線中,催化劑Pt/MnO_2-R的起始電位大約為0.34 V,比Pt/MnO_2-C和Pt/MnO_2-P催化劑的起始電位分別負(fù)移了近70和100 mV。三種催化劑中,Pt/MnO_2-R催化劑具有最高的本征活性(IA),為30.46 A m-2,分別是Pt/MnO_2-C催化劑(16.21 A m-2)和Pt/MnO_2-P催化劑(10.60 A m-2)的2.31和3.53倍。以二氧化錳納米棒為載體的Pt/MnO_2-R催化劑樣品具有更高的抗CO中毒能力和高的氧化甲醇的催化能力以及穩(wěn)定性。MnO_2與Pt間的協(xié)同作用/雙功能機(jī)理是提升Pt催化性能的重要因素。3.利用水熱法合成了八面體狀、納米球狀以及立方體狀等不同形貌的二氧化鈰,以此作為Pt催化劑的助劑/載體制備了Pt-CeO_2/C催化劑,分別記作Pt-CeO_2/C-O、Pt-CeO_2/C-S300、Pt-CeO_2/C-S400、Pt-CeO_2/C-S500和Pt-CeO_2/C-C,并在堿性電解質(zhì)中測(cè)試了其對(duì)甲醇電催化氧化的性能,考察了不同焙燒溫度對(duì)納米球狀CeO_2助催化性能的影響。研究發(fā)現(xiàn),不同形貌的氧化鈰對(duì)Pt/C催化劑具有顯著不同的助催化作用。在三種不同形貌的CeO_2助劑摻雜的催化劑中,Pt-CeO_2/C-S400催化劑對(duì)甲醇的催化氧化表現(xiàn)了更高的催化活性和穩(wěn)定性,我們分析這可能與氧化鈰的粒徑相對(duì)較小和粗糙的表面結(jié)構(gòu)有關(guān)。氧化鈰助劑的粗糙表面結(jié)構(gòu)一方面使其具有較大的表面積,增加了助劑和Pt間的相互作用;另一方面,助劑粗糙的表面結(jié)構(gòu)使與其密切接觸的Pt的表面配位不飽和原子增多,活性位點(diǎn)增加,因此對(duì)甲醇的催化氧化性能增強(qiáng)。
[Abstract]:Pt is the most commonly used anodic catalytic material for direct methanol fuel cells. In recent years, the excellent catalytic performance of Pt can not be replaced by other common metals. However, the problems of Pt catalyst are obvious. Pt is not only expensive but also easy to be produced by the process of methanol oxidation. In order to reduce the cost of catalyst, improve the catalytic activity and anti-CO poisoning ability of Pt catalyst, the method of adding the second component/promoter (metal or metal oxide) to Pt catalyst was adopted. The electronic effect and synergistic effect between Pt and promoter were used to adjust the Pt table. The specific results are as follows: 1. A series of supported non-alloy bimetallic catalysts Pt m Au/RGO (m for Pt/Au atomic ratio, M = 0.5~2.0) with different molar ratios were prepared by liquid-phase CO-reduction using graphene as support. Au promoter was used to catalyze the oxidation of methanol by Pt catalyst in alkaline electrolyte. The morphology, crystal structure and electronic structure of the catalyst were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical measurement techniques such as electrochemical measurement. Cyclic voltammetry and chronoamperometry were used to test the catalytic performance of Pt catalyst. The results showed that the addition of Au could significantly improve the anti-CO poisoning ability of Pt catalyst in alkaline medium and the electrocatalytic performance for methanol oxidation. The catalytic performance of a series of Pt m Au/RGO catalysts has a volcanic relationship with the m value of the catalysts. In this experiment, when the Pt/Au atom ratio is 1.0, the catalysts have the highest electrocatalytic activity and electrochemical stability. The Pt 1.0Au/RGO catalyst sample has the most negative initial potential (-0.78 V) and the Pt/RGO (-0.64 V) phase. Compared with Pt/RGO (0.30 A mg-1 Pt + Au), Pt 0.5 Au / RGO (0.50 A mg-1 Pt + Au), Pt 0.5 Au / RGO (0.50 A mg-1 Pt + Au), Pt 0.8 Au / RGO (0.70 A mg-1 Pt + Au) and Pt 2.0Au / RGO (0.41 A mg-1 Pt + Au) U / RGO (0.41 A mg-1 Pt + Au) were 2.70, 1.70, 1.62, 1.15, 1.15 and 1.97 times and 1.97 times higher than those of Pt / RGO (0.70, 1.70, 1.62, 1.15 and 1.97 times, 1.97 times, respectively) Nanosheets, coral-like and Three kinds of P t/MnO_2 catalysts were prepared by adding nanorod-like manganese dioxide as promoter/carrier into P t catalyst. They were recorded as P t/MnO_2-P, P t/MnO_2-C and P t/MnO_2-R, respectively. The effects of different morphologies of MnO_2 support on the catalytic performance of P T were studied. The samples were characterized by SEM, TEM, XRD and so on. Electrocatalytic oxidation of methanol was studied in acidic electrolytes. The results showed that the interaction between MnO_2 carriers with different morphologies and Pt particles was different, and the catalytic effect on methanol oxidation was different. In CO stripping voltammetry curve, the initial potential of Pt/MnO_2-R was about 0.34 V, which was higher than that of Pt/MnO_2-C and P. Among the three catalysts, P t/MnO_2-R catalyst had the highest intrinsic activity (IA) of 30.46 A m-2, which was 2.31 and 3.53 times of P t/MnO_2-C catalyst (16.21 A m-2) and P t/MnO_2-P catalyst (10.60 A m-2), respectively. The synergistic / bifunctional mechanism between MnO_2 and Pt is an important factor to improve the catalytic performance of Pt. 3. Octahedral, nanospherical and cubic cerium dioxide with different morphologies were synthesized by hydrothermal method and used as Pt catalyst. Pt-CeO_2/C catalysts were prepared as Pt-CeO_2/C-O, Pt-CeO_2/C-S300, Pt-CeO_2/C-S400, Pt-CeO_2/C-S500 and Pt-CeO_2/C-C-C, respectively. The effects of calcination temperature on the catalytic performance of nanospherical CeO_2 were investigated in alkaline electrolytes. C eO_2/C-S400 catalysts exhibited higher catalytic activity and stability for the catalytic oxidation of methanol in three different morphologies of C eO_2-doped catalysts, which may be related to the relatively small particle size and rough surface structure of C eO_2. On the one hand, the rough surface structure of ceria promoter makes it have a larger surface area, which increases the interaction between the promoter and Pt. On the other hand, the rough surface structure of ceria promoter increases the surface coordination unsaturated atoms and active sites of Pt which is in close contact with it, so the catalytic oxidation performance of methanol is enhanced.
【學(xué)位授予單位】：曲阜師范大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TM911.4;TQ426

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本文編號(hào)：2190037