發(fā)布時(shí)間：2018-06-25 11:41

  本文選題：鐵離子 + 燃料電池��； 參考：《湖南科技大學(xué)》2017年碩士論文

【摘要】：直接醇燃料電池(DAFC)或直接甲酸燃料電池(DFAFC)是一類綠色環(huán)保、高能量密度和能量轉(zhuǎn)換密度高的新型電池,近年來受到了廣泛的關(guān)注。這些電池的陰極使用氧氣(或空氣)作為氧化劑發(fā)生還原,即氧還原反應(yīng)(ORR)。然而,即使使用目前催化效果最好的Pt和Pt基催化劑,ORR仍然是一個(gè)非常緩慢的過程。這降低了電池的放電性能,同時(shí)提高了電池的成本。盡管在ORR催化劑方面已經(jīng)進(jìn)行了很多優(yōu)秀的工作,但是提高燃料電池性能的關(guān)鍵性問題仍然亟待解決。因此,尋找其他的氧化劑替代氧氣(或空氣)具有非常重大的意義。Fe~(3+)是另一個(gè)可替代的氧化劑,它具有原料來源廣泛、穩(wěn)定性高和氧化還原電位(E0(Fe~(3+)/Fe~(2+))=0.771V vs SHE)較高等諸多特點(diǎn)。Fe~(3+)在一些常見的催化劑存在下就能很容易地被還原為Fe~(2+),這是因?yàn)镕e~(3+)/Fe~(2+)具有較高的交換電流密度,Fe~(3+)/Fe~(2+)電對(duì)之間的轉(zhuǎn)換屬于可逆的電化學(xué)過程。碳、石墨、鉑等已經(jīng)被證實(shí)是Fe~(3+)/Fe~(2+)之間氧化還原反應(yīng)的高效催化劑。另外,對(duì)燃料高效氧化是保證燃料電池穩(wěn)定工作的關(guān)鍵點(diǎn)之一。在堿性條件下,Pd和Pd基催化劑已被證明對(duì)醇(或甲酸)氧化具有較好的電催化性能,目前,Pd及其Pd基催化劑對(duì)醇(甲酸)氧化都已經(jīng)做了相當(dāng)多的研究,包括Pd Au、Pd Ni、Pd Sn等,這些催化劑的金屬顆粒分散性很好,并且具有優(yōu)異的電催化性能。在本論文的研究中,制備了新穎的鈀基電催化劑,研究了它們的電催化性能;將它們應(yīng)用于以Fe~(3+)為氧化劑的新型燃料電池,研究了電池的放電性能。(1)采用化學(xué)還原法,以β-環(huán)糊精(β-cd)修飾的碳納米管(b-cd-CNT或者β-cd-C)為載體,在乙二醇溶液中負(fù)載Pd或者Pd Sn納米顆粒,制備Pd Sn/b-cd-CNT,Pd Sn/CNT,Pd/b-cd-CNT,Pd/CNT和Pd/b-cd-C催化劑。通過TEM和XRD對(duì)催化劑進(jìn)行表征,采用循環(huán)伏安和計(jì)時(shí)電流等方法對(duì)催化劑的電化學(xué)性能進(jìn)行測(cè)試,在堿性條件下,分別測(cè)試了這些催化劑對(duì)C1-C3醇氧化的性能。結(jié)果表明:Pd Sn/b-cd-CNT催化劑對(duì)甲醇、乙醇、正丙醇和異丙醇的氧化都有非常強(qiáng)的電催化性能,峰電流密度分別為94、145、184和87 m A?cm-2。(2)采用包覆法制備不同F(xiàn)e_3O_4含量的Fe_3O_4-C載體,然后利用化學(xué)還原法制備Fe_3O_4-C負(fù)載的Pd Sn納米催化劑(Pd Sn/Fe_3O_4-C)。采用透射電鏡(TEM)和X射線衍射(XRD)技術(shù)對(duì)Pd Sn納米催化劑顆粒的物理性能進(jìn)行表征;采用循環(huán)伏安法(CV)、計(jì)時(shí)電流法(CA)和交流阻抗(EIS)技術(shù)研究了催化劑在堿性條件下對(duì)乙醇氧化的電催化活性。結(jié)果表明,Pd Sn納米金屬顆粒在Fe_3O_4-C載體上具有較好的分散性.在所制備的催化劑(Pd Sn/Fe_3O_4(2%)-C、Pd Sn/Fe_3O_4(5%)-C、Pd Sn/Fe_3O_4(10%)-C)中、Pd Sn/Fe_3O_4(5%)-C催化劑對(duì)乙醇氧化表現(xiàn)出較高的電催化活性,乙醇氧化的峰電流密度達(dá)到147m A cm-2,并且Fe_3O_4的加入提高了催化劑的電化學(xué)穩(wěn)定性。相比于Pd/C,Pd Sn/Fe_3O_4(5%)-C對(duì)乙醇氧化反應(yīng)的電荷轉(zhuǎn)移阻力也有大幅度下降。(3)以鐵離子為氧化劑取代氧氣,制備了新型醇燃料電池。測(cè)試了不同陽極催化劑Pd Sn/Fe_3O_4(5%)-C、Pd Sn/b-cd-CNT,Pd Sn/CNT、Pd/b-cd-CNT、Pd/CNT、Pd/b-cd-C和商業(yè)Pd/C在不同醇溶液中的放電性能,包括甲醇、乙醇、正丙醇和異丙醇。陰極反應(yīng)為鐵離子在碳粉電極上進(jìn)行還原。陽極液(醇+1 mol L-1Na OH)和陰極液(Fe~(3+)+0.5 mol L-1Na Cl)之間通過Nafion 117膜隔開。結(jié)果表明:以Pd Sn/b-cd-CNT為陽極催化劑時(shí),開路電壓在1.14~1.22 V,在甲醇、乙醇、正丙醇和異丙醇中放電功率密度分別為15.2、16.1、19.9和12.2 m W?cm-2。以Pd Sn/Fe_3O_4(5%)-C為陽極催化劑,乙醇為燃料時(shí),開路電壓為1.20 V,放電功率密度為18.0 m W?cm-2。(4)以甲酸為燃料、Fe~(3+)為氧化劑組成了一種新型的甲酸/鐵離子燃料電池。陽極催化劑為多壁碳納米管(MWCNT)以及β-環(huán)糊精(β-CD)修飾的MWCNT(β-CD-MWCNT)負(fù)載的金屬鈀/錫納米顆粒:Pd/MWCNT、Pd Sn/MWCNT、Pd/β-CD-MWCNT和Pd Sn/β-CD-MWCNT。運(yùn)用循環(huán)伏安(CV)和計(jì)時(shí)電流(CA)等技術(shù),研究了它們?cè)趬A性條件下對(duì)甲酸氧化反應(yīng)的電催化活性。結(jié)果表明,加入適量的金屬錫能促進(jìn)鈀對(duì)甲酸的電催化氧化,甲酸氧化電位提前,電流密度增加,環(huán)糊精的改性對(duì)催化劑電催化活性有一定提升。將上述催化劑制成電池陽極片,碳粉制成電極陰極片,組成甲酸/鐵離子燃料電池并測(cè)試其放電性能。電池的開路電壓在0.98~1.2 V之間;以Pd Sn/β-CD-MWCNT為陽極時(shí),其最大放電電流密度達(dá)50 m A?cm-2,最大功率密度達(dá)12.6 m W?cm-2,遠(yuǎn)遠(yuǎn)優(yōu)于以Pd/C為陽極的電池性能。
[Abstract]:Direct alcohol fuel cell (DAFC) or direct formic acid fuel cell (DFAFC) is a new type of green, high energy density and high energy conversion density, which has been widely paid attention in recent years. The cathode of these batteries is reduced by oxygen (or air) as oxidant, that is, oxygen reduction reaction (ORR). However, even using current catalysis The best Pt and Pt based catalysts, ORR is still a very slow process. This reduces the discharge performance of the battery and increases the cost of the battery. Although many excellent work has been done on the ORR catalyst, the key questions to improve the performance of the fuel cell are still to be solved. The substitute of oxygen (or air) is of great significance..Fe~ (3+) is an alternative oxidant. It has a wide range of raw materials, high stability, and redox potential (E0 (Fe~ (3+) /Fe~ (2+)) =0.771V vs SHE) and a good many characteristics.Fe~ (3+) can be easily reduced to a number of common catalysts. Because Fe~ (3+) /Fe~ (2+) has high exchange current density, the conversion between Fe~ (3+) /Fe~ (2+) electric pairs is a reversible electrochemical process. Carbon, graphite, platinum, etc. have been proved to be efficient catalysts for the redox reaction between Fe~ (3+) /Fe~ (2+). In addition, the efficient oxidation of fuel is one of the key points to ensure the stability of fuel cells. Under alkaline conditions, Pd and Pd based catalysts have been proved to have good electrocatalytic properties for alcohols (or formic acid) oxidation. At present, Pd and its Pd based catalysts have done quite a lot of research on alcohols (formic acid) oxidation, including Pd Au, Pd Ni, Pd Sn and so on. These catalysts have good dispersibility of metal particles and have excellent electrocatalytic properties. In this study, a novel palladium based electrocatalyst was prepared and their electrocatalytic properties were studied. They were applied to a new type of fuel cell with Fe~ (3+) as oxidant. (1) the chemical reduction method was used to use the carbon nanotubes (b-cd-CNT or beta -cd-C) modified by beta cyclodextrin (beta -cd) as the carrier, in B two. Pd or Pd Sn nanoparticles were loaded in the alcohol solution to prepare Pd Sn/b-cd-CNT, Pd Sn/CNT, Pd/b-cd-CNT, Pd/CNT and Pd/b-cd-C catalysts. The catalysts were characterized by TEM and XRD. The electrochemical properties of the catalysts were tested by cyclic voltammetry and chronoampere, and the catalysts were tested under alkaline conditions. The performance of alcohol oxidation shows that Pd Sn/b-cd-CNT catalysts have very strong electrocatalytic properties for methanol, ethanol, propanol and isopropanol. Peak current density is 94145184 and 87 m A? Cm-2. (2), respectively, to prepare Fe_3O_4-C carrier with different Fe_3O_4 content by coating method, and then use chemical reduction method to prepare P of Fe_3O_4-C load. D Sn nano catalyst (Pd Sn/Fe_3O_4-C). The physical properties of Pd Sn nano catalyst particles were characterized by transmission electron microscopy (TEM) and X ray diffraction (XRD). The electrocatalytic activity of the catalyst on the oxidation of ethanol under alkaline conditions was studied by cyclic voltammetry (CV), chronoamperometric (CA) and AC impedance (EIS) technology. D Sn nanoparticles have good dispersibility on Fe_3O_4-C carriers. In the prepared catalysts (Pd Sn/Fe_3O_4 (2%) -C, Pd Sn/Fe_3O_4 (5%) -C, Pd Sn/Fe_3O_4 (10%) -C), the catalysts exhibit higher electrocatalytic activity for ethanol oxidation. The electrochemical stability of the catalyst was improved. Compared to Pd/C, the charge transfer resistance of Pd Sn/Fe_3O_4 (5%) -C to ethanol oxidation was also greatly reduced. (3) a new alcohol fuel cell was prepared by replacing oxygen with iron ions as an oxidant. The different anode catalysts, Pd Sn/Fe_3O_4 (5%) -C, Pd Sn/b-cd-CNT, Pd Sn/CNT, Pd/b-cd-CN, were tested. The discharge performance of T, Pd/CNT, Pd/b-cd-C and commercial Pd/C in different alcohol solutions, including methanol, ethanol, n-propanol and isopropanol. The reaction of the cathode to the reduction of the iron ions on the carbon electrode. The anode solution (alcohol +1 mol L-1Na OH) and the cathode liquid (Fe~ (3+) +0.5 mol) are separated by the 117 membrane. When the anode catalyst is used, the open circuit voltage is at 1.14~1.22 V, the discharge power density in methanol, ethanol, propanol and isopropanol is 15.2,16.1,19.9 and 12.2 m W? Cm-2. with Pd Sn/Fe_3O_4 (5%) -C as the anode catalyst. When ethanol is used as fuel, the open circuit voltage is 1.20 V and the discharge power density is 18 m W? 4 with formic acid as the fuel. A new type of formic acid / iron ion fuel cell is formed. The anode catalyst is the metal palladium / tin nanoparticles loaded with multi wall carbon nanotubes (MWCNT) and beta cyclodextrin (beta -CD) modified MWCNT (beta -CD-MWCNT): Pd/MWCNT, Pd Sn/MWCNT, Pd/ beta -CD-MWCNT and Pd Sn/ beta -CD-MWCNT. using cyclic voltammetry and timing current. The results show that the electrocatalytic oxidation of palladium to formic acid can be promoted by adding a proper amount of metal tin, the oxidation potential of formic acid is ahead of time, the current density increases, the modification of cyclodextrin has a certain increase in the electrocatalytic activity of the catalyst. The catalyst is made into a battery anode and carbon powder. The electrode cathode is made to form a formic acid / iron ion fuel cell and test its discharge performance. The open circuit voltage of the battery is between 0.98~1.2 V; the maximum discharge current density of Pd Sn/ beta -CD-MWCNT is 50 m A cm-2, the maximum power density reaches 12.6 m W? Cm-2, far superior to the battery performance with Pd/C as the anode.
【學(xué)位授予單位】：湖南科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：O643.36;TM911.4

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