导电聚合物和Pt纳米颗粒所形成的复合电极电催化氧化甲醇行为的研究

发布时间：2018-05-29 10:42

本文选题：甲醇氧化 + Pt纳米颗粒　；参考：《华东师范大学》2015年硕士论文

【摘要】：近几十年来,由于科技的迅猛发展,对能量的需求日益增加,化石燃料的迅速减少以及环境污染的日益加重,使得探寻一种能量转换率高,低或零排放量的燃料电池,已经逐渐成为人们目前研究的热点。氢气燃料电池作为一种高能燃料电池,除了需考虑它的经济成本、可靠性和耐久性外,目前还需面临氢气的生产、储存和运输等问题,而直接甲醇燃料电池(DMFCs)是以可再生的液体甲醇作为燃料,与氢气燃料电池相比具有原料便于储存、运输、安全和电池装置简单等优势。目前,在酸性条件下,DMFC中对甲醇的电催化氧化具有最好电催化活性的催化剂是Pt及其合金,但Pt是一种贵金属催化剂且其电催化氧化甲醇的效率与许多因素有关,其中负载Pt纳米颗粒的电极材料的种类及其表面状况对提高Pt纳米颗粒电催化氧化甲醇的效率就具有非常重要的影响；同时,在DMFC中,甲醇的电极氧化是一个极其复杂且缓慢的过程,将会产生许多诸如CO和CHO等易吸附在电极表面的中间体而降低电极的电催化活性。因此,探寻一种具有较大比表面积的Pt底电极材料,用以减小Pt纳米颗粒的负载量,增加其分散度,提高其电催化氧化甲醇的效率和抗中毒能力已经成为目前的研究热点。本论文分别选取了将聚苯胺(PANI)、聚邻甲基苯胺(POT)、聚邻甲氧基苯胺(POMA)、多壁碳纳米管(MWCNT)和分别掺杂有不同含量的多壁碳纳米管(MWCNT),石墨烯(GRA),电池活性碳(YBC)和电容活性碳(YEC)的石墨粉碳糊材料作为负载Pt纳米颗粒的底电极,主要尝试着从以下四个方面探究了负载Pt纳米颗粒的底电极种类及其制备条件对其所负载的Pt纳米颗粒电催化氧化甲醇活性的影响。(1)比较Pt/PANI/GC(玻碳电极)、Pt/POT/GC 和 Pt/POMA/GC电催化氧化甲醇的活性利用循环伏安法、在线紫外-可见光谱和交流阻抗等技术比较性地探究了具有不同膜厚度的PANI、POT和POMA膜结构的差异性和导电性。通过恒电位电沉积法分别成功地制备出了具有不同膜厚度的PANI、POT和POMA修饰的Pt/PANI/GC、Pt/POT/GC和Pt/POMA/GC复合电极。利用SEM表征了这些复合电极上Pt纳米颗粒的形貌,利用循环伏安法测试了这些复合电极的电化学活性比表面积(EASA)以及这些复合电极电催化氧化甲醇的活性大小。研究发现具有不同膜厚度的Pt/PANI/GC、Pt/POT/GC 和 Pt/POMA/GC上的Pt纳米颗粒分别呈现出不同的形貌,这三种复合电极电催化氧化甲醇的活性均先随着各相应聚合物膜厚度的增大而增大,当聚合物膜厚度超过一定值之后,又随着聚合物膜厚度的增加而逐渐减小,除Pt/POMA/GC外,Pt/POT/GC和Pt/PANI/G C电催化氧化甲醇的活性大小随其各自膜厚度的变化趋势刚好和这两复合电极上各自EASA随其各自膜厚度变化的趋势相同,其中Pt/POT/GC对甲醇的电催化氧化具有最好的电催化活性,其次分别为Pt/PANI/GC 和 Pt/POMA/GC.(2) Pt/POT/GC的制备条件对其电催化氧化甲醇活性的影响利用循环伏安法详细探究POT膜的不同制备方法(循环伏安和恒电位法)、膜的电沉积电位、膜厚度以及Pt纳米颗粒在这些POT膜上的不同电沉积电位对Pt/POT/GC复合电极电催化氧化甲醇活性的影响。研究发现POT的膜结构和电化学活性均随着其制备条件的变化而变,Pt纳米颗粒在POT/GC上的电沉积行为也受其电沉积电位的影响,而这些因素都将会影响Pt/POT/GC复合电极电催化氧化甲醇的电化学活性。实验结果表明,当Pt的电沉积电位为-100mV, POT的膜沉积电量为4.5mC时(0.85V恒电位制备条件下), Pt/POT(4.5mC)/GC复合电极对甲醇的电催化氧化活性最高。(3) Pt 在 POT/MWCNT/GC上的电沉积行为及其电催化氧化甲醇的活性通过恒电位电沉积法成功地制备出了Pt/POT/MWCNT/GC复合电极,并采用SEM表征了复合电极上Pt纳米颗粒的形貌,采用循环伏安法和恒电位法探究了POT的膜结构特点以及膜厚度对Pt/POT/MWCNT/GC复合电极电催化氧化甲醇活性的影响以及甲醇在这种复合电极上的氧化动力学的过程。由于MWCNT的存在,增大了POT电沉积时的电极表面积,所以与纯GC电极相比,POT在MWCNT/GC上的聚合速度明显的较纯GC电极上的快,且其电化学活性也明显的较纯GC电极上的高。Pt纳米颗粒在具有不同膜厚度的POT/MWCNT/GC 上具有不同的电沉积行为,它能影响Pt纳米颗粒在这些复合底电极上的电沉积形貌、颗粒大小和分散度,进而能影响其电催化氧化甲醇的电催化活性,其中当POT的膜沉积电量为1.0mC, Pt/POT(1.0mC)/MWCNT/GC电催化氧化甲醇的活性最好。甲醇氧化的动力学研究表明,低扫速下(10～100m Vs-1),甲醇在Pt/POT/MWCNT/GC上的氧化动力学过程由甲醇的扩散所控制,而高扫速下(200-1200mVs-1),甲醇在Pt/POT/MWCNT/GC上的氧化动力学过程由甲醇的扩散和吸附共同作用。(4)Pt与各种碳掺杂的石墨碳糊所行成的复合电极电催化氧化甲醇的活性首先,以石墨粉和液态石蜡油为主要原料,成功地制备出了稳定的纯碳糊底电极(CPE)和分别掺杂有不同含量的多壁碳纳米管(MWCNT)、石墨烯(GRA)、电池活性碳(YBC)和电容活性碳(YEC)的掺杂型碳糊底电极Y+CPE(其中Y指上述各掺杂碳材料)以及有不同膜厚度的POT膜修饰的POT/CPE和POT/YBC(14%)+CPE(YBC掺杂的质量分数为14%)碳糊底电极,在整个碳糊底电极的制备过程中,保持石墨粉混合物的总质量为0.5g,石蜡油的质量为0.325g不变。然后再通过恒电位电解的方法将Pt纳米颗粒电沉积在上述所形成的各种碳糊底电极上,制备出各种相应的Pt/Y+CPE, Pt/POT/CPE和 Pt/POT/YBC(14%)+CPE复合电极,并通过SEM表征了这些复合电极上Pt纳米颗粒的形貌,循环伏安法测试了这些复合电极的EASA和这些复合电极电催化氧化甲醇的活性。研究表明,当POT的膜沉积电量为6.5mC, YBC的掺杂质量百分数为14%时,所得的Pt/POT/YBC(14%)+CPE电极对甲醇具有较好的电催化活性。
[Abstract]:In recent decades, due to the rapid development of science and technology, the increasing demand for energy, the rapid reduction of fossil fuels and the increasing pollution of the environment, the exploration of a fuel cell with high energy conversion rate, low or zero discharge volume has gradually become a hot spot of research. Hydrogen fuel cell is a high-energy fuel electric power. In addition to considering its economic cost, reliability and durability, the pool needs to face the problems of hydrogen production, storage and transportation, while the direct methanol fuel cell (DMFCs) is a renewable liquid methanol as fuel. Compared with the hydrogen fuel cell, it has the advantages of easy storage, transportation, safety and simple battery devices. In the acid condition, Pt and its alloy have the best electrocatalytic activity for electrocatalytic oxidation of methanol in DMFC, but Pt is a kind of noble metal catalyst and the efficiency of electrocatalytic oxidation of methanol is related to many factors. The type of electrode materials loaded with Pt nanoparticles and the surface condition of the catalysts are used to improve the electricity of Pt nanoparticles. The efficiency of catalytic oxidation of methanol has a very important effect. At the same time, in DMFC, the electrode oxidation of methanol is a very complicated and slow process, which will produce a lot of intermediates, such as CO and CHO, which are easily adsorbed on the surface of the electrode and reduce the electrocatalytic activity of the electrode. For this reason, a kind of Pt bottom electricity with a larger specific surface area is explored. Polar materials are used to reduce the load of Pt nanoparticles, increase their dispersion, improve the efficiency of electrocatalytic oxidation of methanol and the ability to resist poisoning. In this paper, polyaniline (PANI), poly o-methylaniline (POT), polyo-methoxy aniline (POMA) and multi walled carbon nanotubes (MWCNT) were selected respectively. Graphite powder carbon paste materials with different content of multi wall carbon nanotubes (MWCNT), graphene (GRA), battery active carbon (YBC) and capacitive active carbon (YEC) are used as the bottom electrodes for loading Pt nanoparticles. The main purpose of this study is to explore the type of the bottom electrode of the loaded Pt nanoparticles and the Pt nanoparticles loaded by the preparation conditions from the following four aspects. The effects of catalytic oxidation of methanol. (1) compared Pt/PANI/GC (glassy carbon electrode), Pt/POT/GC and Pt/POMA/GC electrocatalytic oxidation of methanol by cyclic voltammetry, on-line UV visible spectroscopy and AC impedance techniques, the differences and conductivity of PANI, POT and POMA membrane structures with different film thickness were compared. PANI, POT and POMA modified Pt/PANI/GC, Pt/POT/GC and Pt/POMA/GC composite electrodes with different film thickness were successfully prepared by electrodeposition. The morphology of Pt nanoparticles on these composite electrodes was characterized by SEM, and the electrochemical activity specific surface area (EASA) of these composite electrodes and these complex electrodes were measured by cyclic voltammetry. It is found that the Pt nanoparticles with different thickness of Pt/PANI/GC, Pt/POT/GC and Pt/POMA/GC exhibit different morphology respectively. The activity of electrocatalytic oxidation of methanol at the three composite electrodes first increases with the increase of the thickness of the corresponding polymer films, when the thickness of the polymer film is the thickness of the polymer membrane. After more than a certain value, with the increase of the thickness of the polymer film, in addition to the Pt/POMA/GC, the Pt/POT/GC and Pt/PANI/G C electrocatalytic oxidation of methanol has the same tendency to change with the thickness of their respective membrane, and the same trend of the change of the thickness of each membrane on the two composite electrode with their respective film thickness, of which Pt/POT/GC has the electricity of methanol. Catalytic oxidation has the best electrocatalytic activity, followed by the effects of the preparation conditions of Pt/PANI/GC and Pt/POMA/GC. (2) Pt/POT/GC on the activity of electrocatalytic oxidation of methanol, using cyclic voltammetry to explore the different preparation methods of POT films (cyclic voltammetry and constant potential method), the electrodeposition potential of the membrane, the thickness of the membrane and the Pt nanoparticles. The effect of different electrodeposition potentials on these POT films on the electrocatalytic oxidation of methanol by Pt/POT/GC composite electrode has been studied. It is found that the membrane structure and electrochemical activity of POT change with the change of the preparation conditions. The electrodeposition behavior of Pt nanoparticles on POT/GC is also influenced by the electrodeposition potential, and these factors will affect Pt/POT. The electrochemical activity of methanol was oxidized by /GC composite electrode. The experimental results showed that the electrocatalytic oxidation activity of Pt/POT (4.5mC) /GC composite electrode to methanol was the highest when the electrodeposition potential of Pt was -100mV and the deposition of POT was 4.5mC (0.85V constant potential). (3) the electrodeposition behavior of Pt in POT/MWCNT/GC and its electrical activity The Pt/POT/MWCNT/GC composite electrode was successfully prepared by constant potential electrodeposition, and the morphology of Pt nanoparticles on the composite electrode was characterized by SEM. The membrane structure characteristics of POT and the electrocatalytic oxidation of methanol to Pt/POT/ MWCNT/GC composite electrode were investigated by cyclic voltammetry and constant potential method. The effect of the oxidation kinetics of methanol on this composite electrode. Because of the presence of MWCNT, the electrode surface area of POT electrodeposition is increased, so compared with the pure GC electrode, the polymerization speed of POT on MWCNT/GC is obviously faster than that on the pure GC electrode, and its electrochemical activity is obviously higher than the high.Pt nanoscale on the pure GC electrode. The particles have different electrodeposition behavior on POT/MWCNT/GC with different film thickness. It can affect the electrodeposition morphology, particle size and dispersion of Pt nanoparticles on these composite bottom electrodes, which can affect the electrocatalytic activity of the electrocatalytic oxidation of methanol, when the deposition of POT is 1.0mC, Pt/POT (1.0mC) /MWCNT/GC electricity. Catalytic oxidation of methanol is the best activity. The kinetic study of methanol oxidation shows that the oxidation kinetics of methanol on Pt/POT/MWCNT/GC under low sweep rate (10 ~ 100m Vs-1) is controlled by the diffusion of methanol, while high sweep speed (200-1200mVs-1), the oxidation kinetics of methanol on Pt/POT/MWCNT/GC is made by the diffusion and adsorption of methanol together. (4) the activity of Pt and various carbon doped graphite carbon paste by electrocatalytic oxidation of methanol is first made by graphite powder and liquid paraffin oil as the main material. A stable pure carbon paste bottom electrode (CPE) and different content of multi walled carbon nanotubes (MWCNT), graphene (GRA) and battery active carbon (YBC) are successfully prepared. The YEC doped carbon paste bottom electrode Y+CPE (of which Y refers to the above doped carbon materials) and the POT/CPE and POT/YBC (14%) +CPE (YBC doped mass fraction of 14%) modified by POT films with different film thickness, and in the preparation of the whole carbon paste bottom electrode, the total mass of the graphite powder mixture is 0.5g, paraffin wax is maintained. The quality of the oil is 0.325g unchanged. Then the Pt nanoparticles are electrodeposited by electroconstant electrolysis on various carbon paste bottom electrodes formed above, and a variety of corresponding Pt/Y+CPE, Pt/POT/CPE and Pt/POT/YBC (14%) +CPE composite electrodes are prepared. The morphology of Pt nanoparticles on these composite electrodes is characterized by SEM and cyclic voltammetry is characterized by SEM. The results show that the Pt/POT/YBC (14%) +CPE electrode obtained by the EASA (14%) +CPE electrode has good electrocatalytic activity for methanol when the electrokinetic energy of these composite electrodes and the activity of electrocatalytic oxidation of methanol have been tested. The results show that the Pt/POT/YBC (14%) +CPE electrode obtained from the deposition of 6.5mC and the percentage of the doping mass of the YBC is 14%.
【学位授予单位】：华东师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O646.54;TM911.4

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