直接乙醇燃料电池：铂基和钯基电催化剂的研究

发布时间：2018-06-22 02:28

本文选题：EOR + ORR　；参考：《石河子大学》2015年硕士论文

【摘要】：直接乙醇燃料电池(DEFC)具有低污染、理论能量密度高、燃料来源广泛、储存和运输方便等优点,在便携式电源、电动汽车等领域有广范的应用前景,对解决能源短缺和环境污染两大难题有重大的意义。目前DEFC最常用的催化剂是Pt基催化剂,Pt基催化剂对乙醇电化学氧化(EOR)的活性不高,而且EOR反应中产生的中间产物会造成催化剂中毒失活。因此,开发高活性的催化剂对DEFC的发展具有重要意义。而且,由于Pt的价格较高、储量稀少,所以研究负载量低的Pt基催化剂或是非Pt催化剂已势在必行。本文从催化剂的活性、稳定性和制备成本三方面考虑,主要研究了以下内容:(1)本文通过溶剂蒸发法制备了介孔Sn O2,然后利用乙二醇还原法制备了介孔Pt Sn O2/C电催化剂。通过X-射线衍射(XRD),X-射线光电子能谱分析(XPS)、透射电镜(TEM)和电感耦合等离子体原子发射光谱(ICP-AES)等表征手段,对催化剂的形貌和组成元素进行表征。证明了介孔Sn O2和Pt纳米粒子成功的固载在碳载体上。通过电化学性能测试可知,由于介孔Sn O2的加入,虽然催化剂的电化学表面积(ECSA)明显降低了,但活性和抗中毒能力有明显的提高,这是因为和普通的Pt Sn O2/C催化剂相比,介孔Sn O2和Pt纳米粒子的接触面积更大,相互作用也更强,提高了Pt活性位的催化能力,降低了中间产物在Pt活性位的覆盖,减少了催化剂的失活,从而使催化剂的活性和稳定性有了明显的提高。(2)本文结合了囊泡模板法和化学还原法制备了中空结构的Pd Cu纳米球,在常温下以水为溶剂,Vulcan XC-72碳黑为载体制备了中空Pd Cu/C催化剂。通过TEM和高角度环形暗场-扫描透射电子显微镜(HAADF-STEM)对催化剂进行表征,结果表明Pd Cu纳米球是由Pd Cu纳米粒子构成,而且负载后的Pd Cu纳米球仍然保持中空结构。相应的元素映射也证明了Pd、Cu两种元素是均匀分布在中空球上。和Pd/C相比,Pd Cu/C催化剂对氧还原反应(ORR)的催化活性显著提高,经过3000圈CV的稳定性测试,Pd Cu/C催化剂的电流密度下降了24.8%,而且稳定后的电流密度也远高于Pd/C和Pt/C催化剂。中空Pd Cu/C催化剂具有更高的催化活性和稳定性可归因于两方面:一方面,Cu的掺杂提高了Pd的分散度;另一方面,中空结构的纳米粒子和实心纳米颗粒相比,前者的比表面积更大,提供的活性位也更多。(3)本文采用简单的水热法,在聚乙烯吡咯烷酮(PVP)、溴化钾、四氯铂酸钾、氯钯酸钠、氯化铜体系中,通过控制盐酸的量制备了就有高晶面的Pt Pd Cu凹面立方体。通过XRD表征证明了Pt Pd Cu/C-1和Pt Pd Cu/C-2两种催化剂都存在合金相。通过对制备的Pt Pd Cu/C-1和Pt Pd Cu/C-2催化剂进行阴极ORR性能的测试,表明高指数晶面的Pt Pd Cu/C-1和Pt Pd Cu/C-2比Pt/C催化剂更优异的催化活性。这主要归因于其具有更大催化活性位(缺陷位)的高指数晶面以及Pt和其他金属(Cu和Pd)形成合金对催化剂表面电子结构的调变。
[Abstract]:Direct ethanol fuel cell (DEFC) has the advantages of low pollution, high theoretical energy density, wide range of fuel sources, convenient storage and transportation, and has a wide application prospect in portable power supply, electric vehicle and other fields. It is of great significance to solve the problems of energy shortage and environmental pollution. At present, the most commonly used catalyst for DEFC is the Pt based catalyst and the Pt based catalyst has low activity for the electrochemical oxidation of ethanol (EOR), and the intermediate product produced in the EOR reaction will lead to the deactivation of the catalyst. Therefore, the development of high activity catalyst is of great significance to the development of DEFC. Moreover, due to the high price of Pt and the scarcity of its reserves, it is imperative to study Pt based catalysts or non-Pt catalysts with low loading. The main contents are as follows: (1) in this paper, mesoporous Sno _ 2 was prepared by solvent evaporation, and then mesoporous Pt _ Sno _ 2 / C electrocatalyst was prepared by ethylene glycol reduction method. The morphology and composition of the catalyst were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and inductively coupled plasma atomic emission spectrometry (ICP-AES). It was proved that mesoporous Sno _ 2 and Pt nanoparticles were successfully immobilized on carbon support. According to the electrochemical performance test, although the electrochemical surface area (ECSA) of the catalyst decreased obviously, the electrochemical surface area (ECSA) of the catalyst was obviously decreased due to the addition of mesoporous Sno _ 2, but the activity and anti-poisoning ability of the catalyst were significantly improved, which was due to the comparison with the ordinary Pt / Sn _ 2 / C catalyst. The contact area between mesoporous Sno _ 2 and Pt nanoparticles is larger and the interaction is stronger. The catalytic ability of Pt active site is improved, the coverage of intermediate product in Pt active site is reduced, and the deactivation of catalyst is reduced. As a result, the activity and stability of the catalyst were improved obviously. (2) the hollow PD Cu nanospheres were prepared by using vesicle template method and chemical reduction method. Hollow PD Cu / C catalyst was prepared by using water as solvent Vulcan XC-72 carbon black at room temperature. The catalyst was characterized by TEM and high angle ring dark field-scanning electron microscopy (HAADF-STEM). The results showed that the PD Cu nanospheres were composed of PD Cu nanoparticles, and the supported PD Cu nanospheres remained hollow structure. The corresponding element mapping also proves that the two elements of PdCU are uniformly distributed on hollow spheres. Compared with PD / C, the catalytic activity of PD / Cu / C catalyst for oxygen reduction reaction (ORR) was significantly increased. The current density of PD / Cu / C catalyst decreased by 24.8T after 3000 cycles of CV stability test, and the current density after stabilization was much higher than that of PD / C and PtP / C catalysts. The higher catalytic activity and stability of hollow PD / Cu / C catalyst can be attributed to two aspects: on the one hand, the doping of Cu increases the dispersion of PD; on the other hand, the hollow structure nanoparticles are compared with solid nanoparticles. The former has larger specific surface area and more active sites. (3) in the system of polyvinylpyrrolidone (PVP), potassium bromide, potassium tetrachloroplatinate, sodium palladium chloride and copper chloride, a simple hydrothermal method is used. The Pt PD Cu concave cube with high crystal surface was prepared by controlling the amount of hydrochloric acid. XRD results show that there are alloy phases in both Pt PD Cu / C 1 and Pt PD Cu / C 2 catalysts. The cathodic ORR properties of Pt PD Cu / C 1 and Pt PD Cu / C 2 catalysts were tested. The results show that Pt PD Cu / C 1 and Pt PD Cu / C 2 have better catalytic activity than that of Pt / C catalyst. This is mainly attributed to the high exponent crystal surface with larger catalytic activity sites (defect sites) and the modulation of electronic structure on the surface of the catalyst formed by Pt and other metals (Cu and PD).
【学位授予单位】：石河子大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O643.36;TM911.4

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