直接乙醇燃料电池铂、钯基阳极催化剂合成及其机理研究

发布时间：2018-05-19 03:15

本文选题：直接乙醇燃料电池 + 阳极催化剂　；参考：《福州大学》2014年博士论文

【摘要】：直接乙醇燃料电池(DEFC)是一种非常有前景的燃料电池技术,有望应用于移动电子设备、电动汽车和发电站等。目前阻碍DEFC应用发展的主要原因是阳极催化剂的催化反应活性低并且价格高昂。本文主要寻找DEFC阳极催化剂的新材料和新制备方法,利用物理表征所制备的不同催化剂材料具有的合金化程度、平均粒径、形貌、结构和成分组成等物理特性,并研究催化剂的物理特性与对电化学性能之间的构效关系,得到以下主要结果：以MnOx-CNTs复合材料作为载体,采用微波乙二醇还原制备Pt/MnOx-CNTs催化剂。研究表明：Pt纳米颗粒均匀地分散在载体上,其平均粒径2.2nm。催化剂中Mn元素以多种价态形式存在,有利于溶液中H+离子的传递；MnOx-CNTs复合载体中MnOx与CNTs最优的质量含量比为1：1,Pt/MnOx-CNTs (1:1)催化剂在酸性介质中对乙醇电催化氧化的峰电流密度为1141.4 mA mg-1 Pt,是Pt催化剂(626.4 mA mg-1 Pt)的1.8倍,MnOx在乙醇阳极氧化过程中即可以促进脱氢反应,又能够增加含氧物种,明显促进了除去催化剂表面中毒中间产物能力。选择低成本Pd作为基体,通过微波乙二醇法还原制备PdM/C (M=Te, Sb)二元催化剂,研究表明：PdTex/C和PdSbx/C催化剂中存在合金相；加入Te和Sb均能增加催化剂表面含氧物种,提高催化剂对毒性中间产物的氧化除去,促进乙醇吸附和进一步氧化。乙醇电催化氧化峰电流密度在PdTe1.5/C和PdSb0.15/C催化剂上分别为190.3 mA cm-2和117.5 mA cm-2,是Pd/C催化剂的2.8倍和1.7倍。在室温条件下,采用自组装法合成了PdBi/C和Cu@PdCu/C催化剂,研究表明：(1)Bi3+离子容易在Pd粒子上发生不可逆吸附可便捷高效地合成PdBi/C催化剂。Pd吸附Bi后,催化剂粒径相比于吸附前的Pd粒子增大,沉积的Bi物种多以氧化态形式存在,并与Pd之间存在强电子相互作用,并促进Pd对溶液中OH"吸附,提高催化剂氧化毒性中间产物的能力,乙醇阳极氧化峰电流密度在PdBi/C (20:1)催化剂上为180.5 mA cm-2,是Pd/C的2.4倍；(2)通过Pd2+离子和Cu粒子的静电取代合成Cu@PdCu/C催化剂,该催化剂具有Cu内核和PdCu合金外壳层结构,外壳层厚度约为0.5nnm；核壳结构提高了Pd的利用率,且外壳层PdCu合金能够提高催化剂表面含氧物种生成,促进表面毒性物种的氧化去除,从而提高催化剂对乙醇的电催化氧化活性,Cu@PdCu/C催化剂对乙醇电氧化的活性为166.0 mA cm-2,是Pd/C(硼氢化钠还原)的2.8倍。
[Abstract]:Direct ethanol fuel cell (DEFC) is a promising fuel cell technology, which is expected to be used in mobile electronics, electric vehicles and power plants. At present, the main obstacle to the development of DEFC application is the low catalytic activity and high price of the anode catalyst. In this paper, a new material and a new preparation method for DEFC anode catalyst are sought. The physical properties of the different catalyst materials are characterized by physical properties, such as alloying degree, average particle size, morphology, structure and composition. The structure-activity relationship between the physical properties and electrochemical properties of the catalyst was studied. The main results were as follows: the Pt/MnOx-CNTs catalyst was prepared by microwave ethylene glycol reduction with MnOx-CNTs composite as the carrier. The results show that the particles are uniformly dispersed on the support, and the average particle size is 2.2 nm. Mn exists in various valence states in the catalyst. The optimum mass ratio of MnOx to CNTs is 1: 1 Pt- Mn-Ox-CNTs 1: 1) the peak current density of ethanol electrocatalytic oxidation in acidic medium is 1141.4 Ma mg-1 PT, which is Pt catalyst 626.4 Ma mg-1. 1.8-fold MNO _ x can promote the dehydrogenation reaction in the process of ethanol anodic oxidation. It can also increase the oxygen species and obviously promote the ability to remove the intermediate products from the surface poisoning of the catalyst. Using low cost PD as the matrix, the binary catalyst of PdM/C / MMT Te- (SB) was prepared by microwave ethylene glycol reduction. The results showed that there were alloy phases in the catalyst of w / PdTexr / C and PdSbx/C, and the addition of Te and SB could increase the oxygen-containing species on the surface of the catalyst. The oxidation removal of toxic intermediate products by catalyst was improved, and ethanol adsorption and further oxidation were promoted. The peak current density on PdTe1.5/C and PdSb0.15/C is 190.3 Ma cm-2 and 117.5 Ma cm-2 respectively, which is 2.8-fold and 1.7-fold higher than that of Pd/C catalyst. At room temperature, PdBi/C and Cu@PdCu/C catalysts were synthesized by self-assembly method. The results show that the irreversible adsorption of PdBi/C catalyst. PD can easily and efficiently adsorb Bi on PD particles. The particle size of the catalyst is larger than that of the PD particles before adsorption. The deposited Bi species exist in the form of oxidation, and there is a strong electron interaction with PD, which also promotes the adsorption of OH "in solution by PD." The peak current density of ethanol anodic oxidation was 180.5 Ma cm-2 on PdBi/C 20: 1 catalyst, which was 2.4-fold of that of Pd/C. Cu@PdCu/C catalyst was synthesized by electrostatic substitution of Pd2 ion and Cu particle. The catalyst has Cu core and PdCu alloy shell structure, the shell thickness is about 0.5 nm, the core-shell structure increases PD utilization rate, and the shell layer PdCu alloy can improve the formation of oxygen species on the surface of the catalyst and promote the oxidation removal of surface toxic species. Thus, the electrocatalytic oxidation activity of the catalyst for ethanol was improved by 166.0 Ma cm-2, which was 2.8 times higher than that of PD / C (reduction of sodium borohydride).
【学位授予单位】：福州大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：O643.36;TM911.4

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