钯基催化材料对甲酸及肼的电催化氧化研究

发布时间：2018-03-22 21:39

本文选题：直接甲酸燃料电池　切入点：钯基催化剂　出处：《齐鲁工业大学》2015年硕士论文　论文类型：学位论文

【摘要】：在最近几十年,具有众多优点的直接甲酸燃料电池(DFAFC)在全球范围内日益受到关注和重视,许多研究者为提升DFAFC的阳极钯催化剂的电催化性能做出了许多努力。催化剂的电催化性能和催化剂的结构特征、合金组成和载体结构与材料性质等因素有关。本论文从筛选合适的二元钯基合金催化剂和改进催化剂的载体两方面入手来提高DFAFC的阳极电催化剂的催化性能。我们制备了活性碳负载的Pd-Cr、石墨烯负载的Pd催化剂以及玻璃碳基底和Au超微电极上负载的Pd纳米结构,并探索讨论了它们在甲酸的电催化氧化方面的性能；用X-射线衍射光谱(XRD)、原子力显微镜光谱(AFM)、X-射线光电子能谱(XPS)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等方法对催化剂进行了表征；采用循环伏安法(CV),线性扫描法(LSV),计时电流法(CA)等电化学检测方法,测试了各催化剂对甲酸电催化氧化的活性和稳定性。本论文的主要研究内容如下：1.研究了不同原子比的碳载Pd-Cr合金催化剂对甲酸的电催化氧化性能：采用化学还原法,以NaHB4为还原剂制备了不同组分的PdxCr1-x/C (0.6x1)催化剂,并对各催化剂进行了表征和电化学测试。结果表明在钯铬合金中铬的摩尔百分含量占10-40%的时候(即Pd:Cr原子数目比从9:1变化到6:4的整个范围内)比纯Pd对甲酸氧化的催化效果要好,其中以铬的摩尔百分含量约为20%(即Pd:Cr的原子数目比为8:2)时催化效果最好。2.研究了石墨烯负载的Pd (Pd/Graphene)催化剂对甲酸的电催化氧化：首先以改进的Hummers法液相氧化合成氧化石墨烯,然后以NaHB4为还原剂,采用一步还原法制得Pd/Graphene催化剂,并对Pd/Graphene催化剂进行了物理表征和电化学测试。由XRD和TEM可知Pd/Graphene催化剂中Pd纳米粒子的平均直径为3.8 nm。由XPS图谱可知Pd/Graphene催化剂中Pd 3d2/5电子结合能正移了1.6 eV,这说明Pd 3d电子云密度降低了。电化学测试结果表明Pd/Graphene催化剂对甲酸的氧化峰电位较之于Pd/C催化剂负移了150 mV；且在Pd/Graphene催化剂电极上,甲酸氧化的峰电流密度较高、稳定性较好。这一方面是由于Pd纳米粒子尺寸较小,另一方面是由于石墨烯在还原过程中保留了部分含氧基团,这使得催化剂具有较好的亲水性,从而使反应能更好的进行。3.研究了玻璃碳负载的Pd纳米结构和超微电极上负载Pd纳米结构的电氧化行为：采用电沉积的方法分别在玻璃碳和超微电极上电沉积金属钯纳米粒子,并研究它们对甲酸及水合肼的电催化氧化效果。
[Abstract]:In recent decades, DFAFC-based direct formic acid fuel cells (DFAFCs), which have many advantages, have attracted more and more attention all over the world. Many researchers have made great efforts to improve the electrocatalytic performance of DFAFC anode palladium catalysts. The composition of alloy and the structure of support are related to the properties of materials. In this paper, we improve the catalytic performance of DFAFC anodic electrocatalysts by screening suitable binary palladium based alloy catalysts and improving the support of catalysts. We prepared Pd-Cr-supported Pd-Cr, graphene supported PD catalysts and PD nanostructures supported on glass-carbon substrates and au ultraelectrodes. Their properties in the electrocatalytic oxidation of formic acid were also discussed. The catalysts were characterized by means of X-ray diffraction (XRD), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscope (TEM). Electrochemical detection methods such as cyclic voltammetry, linear scanning method, chronoamperometric method and chronoamperometric method were used. The activity and stability of various catalysts for the electrocatalytic oxidation of formic acid were tested. The main contents of this thesis are as follows: 1. The electrocatalytic oxidation of formic acid over carbon-supported Pd-Cr alloy catalysts with different atomic ratios was studied. PdxCr1-x/C _ (0.6 x _ 1) catalyst with different components was prepared by using NaHB4 as reducing agent. The results showed that when the molar percentage of chromium in palladium chromium alloy was 10-40% (that is, the ratio of Pd:Cr atom number changed from 9:1 to 6:4), the oxidation of formic acid by pure PD was higher than that of pure PD. The catalytic effect is good, The best catalytic effect was obtained when the molar percent content of chromium was about 20% (that is, the atomic number ratio of Pd:Cr is 8: 2). The electrocatalytic oxidation of formic acid on graphene supported PD / Graphene catalyst was studied. Firstly, graphene oxide was synthesized by liquid phase oxidation of graphene by improved Hummers method. Then Pd/Graphene catalyst was prepared by one-step reduction with NaHB4 as reductant. The average diameter of PD nanoparticles in Pd/Graphene catalyst was 3.8 nm by XRD and TEM, and the electron binding energy of PD 3d2/5 in Pd/Graphene catalyst was found to be 1.6 EV by XPS spectra. The electron cloud density of PD 3D decreased. The electrochemical results showed that the peak potential of oxidation of formic acid on Pd/Graphene catalyst shifted by 150mV compared with that of Pd/C catalyst, and on the electrode of Pd/Graphene catalyst, The peak current density of formic acid oxidation is higher and the stability is better. This is due to the smaller size of PD nanoparticles and the retention of some oxygen-containing groups in the reduction process of graphene, which makes the catalyst have good hydrophilicity. The electrooxidation behavior of glassy carbon supported PD nanostructures and PD nanostructures loaded on ultramicro electrodes was studied by electrodeposition of palladium nanoparticles on glass carbon and ultramicro electrodes, respectively. The electrocatalytic oxidation of formic acid and hydrazine hydrate was studied.
【学位授予单位】：齐鲁工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O643.36;TM911.4

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