过渡金属掺杂Pt基及Pd基催化剂的制备及其电催化性能研究

发布时间：2018-02-26 16:07

本文关键词： Pt基催化剂 Pd基催化剂过渡金属甲醇甲酸电催化氧化　出处：《烟台大学》2014年硕士论文　论文类型：学位论文

【摘要】：燃料电池是高效、绿色的发电装置，其中直接甲醇燃料电池(DMFC)和直接甲酸燃料电池(DFAFC)被认为是最有应用前景的能源装置。Pt电极是目前常用的DMFC阳极催化剂，在电化学方面显示出良好的催化性能。但Pt资源有限，价格昂贵，且容易吸附CO而导致催化剂中毒，使用寿命缩短。对DFAFC，Pd基催化剂具有很好的电催化活性，但稳定性也有待提高。本论文在优化制备条件的基础上，通过添加Fe、Co、Ni等廉价过渡金属制备了炭黑负载Pt-M及Pd-M双金属催化剂，采用X射线衍射(XRD)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)等分析技术研究了所得催化剂的形貌、结构及表面组成，以循环伏安法(CV)、计时电流法及CO吹扫循环伏安法分别考察了Pt基催化剂对甲醇、Pd基催化剂对甲酸的电催化活性、稳定性及抗CO中毒性能。通过引入天然聚合物壳聚糖分子对炭黑载体进行改性，制备了壳聚糖-炭黑复合物负载Pt及Pd催化剂，并考察了它们对甲醇、甲酸的电催化活性与稳定性。将催化剂的结构与其电催化性能进行关联，论文所得主要结果如下： 1.考察了溶液pH值、Pt负载量及Pt/Ni原子比等制备条件对Pt-Ni/C催化剂用于甲醇电催化氧化反应的影响。结果表明：当溶液pH为9，Pt负载量为5%，Pt/Ni原子比为1:1时所得催化剂具有最好的电催化活性与稳定性。 2. Pt基双金属催化剂对甲醇的电催化氧化活性次序为：Pt/CPt-Fe/CPt-Ni/CPt-Co/C。从几何效应讲，，第二金属的引入使Pt粒子更小、分散更均匀，从而增大了电化学活性面积，提高了Pt的利用率；从电子效应看，第二金属强的给电子效应能使Pt2+浓度减少，Pt0表面百分浓度增加。其中以Co、Ni所表现出的两种效应最好，因此具有最好的催化活性及稳定性。 3. Pd基双金属催化剂对甲酸的电催化氧化活性次序为：Pd/C Pd-Fe/C Pd-Ni/C Pd-Co/C。第二金属的添加可使催化剂颗粒变小、分散度提高。Pd基催化剂具有比Pt基催化剂更高的甲酸氧化活性。 4.壳聚糖可在一定程度上抑制金属颗粒的聚集长大，提高金属的分散度，从而改善Pt催化剂对甲醇、Pd催化剂对甲酸的电催化活性与稳定性。
[Abstract]:Fuel cell is an efficient and green power generation device, in which direct methanol fuel cell (DMFC) and direct formic acid fuel cell (DFAFFC) are considered to be the most promising energy devices. Pt electrode is the commonly used anode catalyst for DMFC. However, Pt has limited resources, high price, easy to adsorb CO and lead to poisoning of catalyst and shorten its service life. It has good electrocatalytic activity for DFAFC- Pd-based catalyst. But stability also needs to be improved. On the basis of optimizing the preparation conditions, Pt-M and Pd-M bimetallic catalysts supported on carbon black were prepared by adding cheap transition metals, such as Feo Co-Ni, etc. The morphology, structure and surface composition of the catalyst were studied by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The electrocatalytic activity of Pt based catalyst for formic acid was investigated by cyclic voltammetry, chronoamperometric method and CO sweep cyclic voltammetry. By introducing natural polymer chitosan molecule to modify carbon black support, Pt and PD catalysts supported on chitosan / carbon black complex were prepared, and their effects on methanol were investigated. The electrocatalytic activity and stability of formic acid. The structure of the catalyst is correlated with its electrocatalytic activity. The main results obtained in this paper are as follows:. 1. The effects of preparation conditions such as pH value of solution, Pt loading and Pt/Ni atom ratio on the electrocatalytic oxidation of methanol over Pt-Ni/C catalyst were investigated. The results showed that the catalyst was prepared when the pH value of the solution was 5 and the Pt / Ni atom ratio was 1: 1. It has the best electrocatalytic activity and stability. 2. The order of electrocatalytic oxidation activity of Pt based bimetallic catalyst for methanol is: Pt / CPt-Fe / CPt-Ni / CPt-Co / C. From the geometry effect, the introduction of the second metal makes Pt particles smaller and more uniform, thus increasing the electrochemical active area and increasing the utilization rate of Pt; From the point of view of electron effect, the strong electron donating effect of the second metal can reduce the concentration of Pt2 and increase the surface concentration of Pt0. Among them, the two effects of Cot0 are the best, so they have the best catalytic activity and stability. 3. The electrocatalytic oxidation activity of PD based bimetallic catalyst for formic acid is in the order of: PD / C Pd-Fe/C Pd-Ni/C Pd-Co / C. the addition of the second metal can make the catalyst particle smaller, and the dispersion of the catalyst increases. The catalyst has higher formic acid oxidation activity than the Pt based catalyst. 4. Chitosan can inhibit the aggregation and growth of metal particles to a certain extent and improve the dispersion of metals, thus improving the electrocatalytic activity and stability of Pt catalysts for methanol and PD catalysts for formic acid.
【学位授予单位】：烟台大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TQ426;TM911.4

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