高稳定性的直接甲醇燃料电池阳极催化剂的制备与研究

发布时间：2018-06-05 04:51

  本文选题：直接甲醇燃料电池 + 甲醇氧化　； 参考：《南京大学》2017年硕士论文

【摘要】：在众多的燃料电池当中,直接甲醇燃料电池(DMFC)以其能量密度高,燃料产量大,便携性好等优点,在移动电源和备用电源方面具有良好的应用前景。然而,提升催化剂的稳定性一直是实现DMFC实用化的重要挑战之一。铂广泛应用在燃料电池催化剂中,但纯铂很容易在催化甲醇氧化的过程中吸附CO等中间产物而丧失活性,目前主要采用助催化剂的方法来设计Pt与其他金属的双金属催化剂来调解催化剂的电子结构,其中PtRu催化剂展现出了良好的催化甲醇氧化活性和抗CO毒化能力,从而获得了广泛的研究。然而,Ru在高电位发生溶解、流失等引起的诸多问题会导致催化剂失活,从而会降低催化剂的稳定性。因此,通过合适的方法来降低PtRu系统中Ru的流失,从而提升催化剂稳定性在目前DMFC阳极催化剂的研究中具有重要意义。本论文主要针对降低Ru流失这一问题,从载体效应和组分效应等方面,减缓金属纳米颗粒迁移、聚集过程,制备出具有高稳定性的DMFC阳极催化剂。主要研究工作如下:一方面,通过对石墨烯在氨气中微波进行氮掺杂,然后用掺氮石墨烯来负载PtRu纳米颗粒。通过XPS表征发现负载铂钌之后掺氮石墨烯N 1s谱峰负移了 0.8 eV,这主要是由于Pt,Ru上的电子向碳载体上的含氮基团上转移造成的,说明氮掺杂之后提升了 PtRu纳米颗粒与载体之间的相互作用。EDS mapping结果显示PtRu纳米颗粒倾向于在N元素周围富集而不是在碳上随机分布。从TEM的结果来看,我们再次发现氮掺杂之后增强了金属和载体之间的相互作用,因此在加速老化测试之后,石墨烯负载铂钌(PtRu/G)纳米催化剂相较于掺氮石墨烯负载铂钌(PtRu/NG)纳米催化剂表面发生了更为严重的金属迁移、聚集的现象。加速老化测试之后,PtRu/NG,商用PtRu/C和PtRu/G在峰电流密度上的衰减分别为33%,43%和45%,在起始电位上的衰减分别为20 mV,190 mV和210 mV,证明PtRu/NG比商用PtRu/C和PtRu/G具有更好的催化甲醇氧化稳定性,尤其是氮掺杂之后明显降低了催化剂起始电位的衰减,说明氮掺杂能够明显降低Ru流失。另一方面,通过浸渍置换的方法在商用PtRu/C中进行Au掺杂从而制备PtRuAu/C催化剂,通过调节浸渍液中氯金酸的浓度控制Au掺杂的含量。通过对不同Au掺杂量的PtRuAu/C催化剂进行甲醇氧化测试,并与商用PtRu/C进行对比,发现微量的Au掺杂并没有降低商用PtRu/C催化活性,但稳定性有显著提高。XPS表征显示Au掺杂之后Pt4f和Ru3p谱峰分别正移了 0.3和0.4eV,这主要是由于Pt,Ru的外层电子受到Au元素的吸引、发生偏移从而增强了金属之间的相互作用。从TEM的结果来看,商用PtRu/C在加速老化测试之后发生明显的金属迁移、聚集的现象,PtRuAu/C-0.5却并不明显。加速老化测试之后,商用PtRu/C峰电流密度衰减了 43%,起始电位衰减了 190 mV,而PtRuAu/C-0.5峰电流密度几乎没有发生衰减,起始电位衰减也仅为10 mV,说明Au掺杂有利于降低Pt的聚集和Ru的流失。
[Abstract]:In many fuel cells, direct methanol fuel cell (DMFC) has the advantages of high energy density, high fuel production and good portability. It has a good application prospect in mobile power and standby power supply. However, the stability of the catalyst is one of the most important challenges for the realization of DMFC application. Platinum is widely used in fuel cells. In the catalyst, pure platinum is easy to adsorb CO and other intermediate products during the catalytic process of methanol oxidation. At present, the main catalyst is used to design the Pt and other metal bimetallic catalysts to mediate the electronic structure of the catalyst, in which the PtRu catalyst exhibits a good catalytic activity of methanol oxidation and the anti CO toxicity. However, a number of problems, such as dissolution of high potential and loss of Ru, will lead to deactivation of the catalyst, which will reduce the stability of the catalyst. Therefore, the loss of Ru in the PtRu system can be reduced by a suitable method, thus improving the stability of the catalyst in the present study of the DMFC anode catalyst. In order to reduce the loss of Ru, this paper reduces the migration and aggregation of metal nanoparticles from the carrier effect and the component effect. The main research work is as follows: on the one hand, the nitrogen doping of graphene in ammonia gas is carried out, and then the use of nitrogen in the ammonia gas is then used. Nitrogen doped graphene was used to load PtRu nanoparticles. The N 1s spectrum peak of nitrogen doped graphene was negatively shifted 0.8 eV after XPS characterization, mainly due to the transfer of electrons from Pt, Ru on the nitrogen group on the carbon carrier, indicating that the interaction of PtRu nanoscale with the carrier and.EDS mapping junction was enhanced after nitrogen doping. The results show that the PtRu nanoparticles tend to be enriched around the N element rather than on the carbon random distribution. From the TEM results, we found that the interaction between the metal and the carrier was enhanced after the nitrogen doping, so the graphite loaded platinum ruthenium (PtRu/G) nano catalyst was loaded with the platinum loaded platinum after the accelerated aging test. After the accelerated aging test, the attenuation of PtRu/NG, commercial PtRu/C and PtRu/G at peak current density is 33%, 43% and 45% respectively, and the attenuation at the initial potential is 20 mV, 190 mV and 210 mV respectively, which proves that PtRu/NG is more than commercial PtRu/C and PtRu/G, and that PtRu/NG is more than commercial PtRu/C and PtRu/G. The good catalytic oxidation stability of methanol, especially after nitrogen doping, obviously reduces the decay of the starting potential of the catalyst, indicating that nitrogen doping can obviously reduce the loss of Ru. On the other hand, the PtRuAu/C catalyst is prepared by Au doping in commercial PtRu/C by impregnation replacement, and Au is controlled by the concentration of chloric acid in the impregnated solution to control Au. Doping content. Through the methanol oxidation test of PtRuAu/C catalyst with different Au doping amount, and comparing with commercial PtRu/C, it is found that the trace Au doping does not reduce the catalytic activity of commercial PtRu/C, but the stability has a significant increase of.XPS characterization that Pt4f and Ru3p spectra peak of Pt4f and Ru3p are shifted 0.3 and 0.4eV respectively, respectively. At Pt, the outer electrons of the Ru are attracted by the Au element, and the interaction between metals is enhanced. From the result of TEM, the commercial PtRu/C has obvious metal migration after the accelerated aging test. The phenomenon of aggregation is not obvious. After accelerating the aging test, the commercial PtRu/C peak current density attenuates by 43. The initial potential attenuated by 190 mV, while the peak current density of PtRuAu/C-0.5 almost did not attenuate and the initial potential decay was only 10 mV, indicating that Au doping was beneficial to reduce the aggregation of Pt and the loss of Ru.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TM911.4
，

本文编号：1980610