本文選題：直接甲醇燃料電池 + 甲醇氧化��； 參考：《南京大學(xué)》2017年碩士論文

【摘要】：在眾多的燃料電池當(dāng)中,直接甲醇燃料電池(DMFC)以其能量密度高,燃料產(chǎn)量大,便攜性好等優(yōu)點(diǎn),在移動(dòng)電源和備用電源方面具有良好的應(yīng)用前景。然而,提升催化劑的穩(wěn)定性一直是實(shí)現(xiàn)DMFC實(shí)用化的重要挑戰(zhàn)之一。鉑廣泛應(yīng)用在燃料電池催化劑中,但純鉑很容易在催化甲醇氧化的過程中吸附CO等中間產(chǎn)物而喪失活性,目前主要采用助催化劑的方法來設(shè)計(jì)Pt與其他金屬的雙金屬催化劑來調(diào)解催化劑的電子結(jié)構(gòu),其中PtRu催化劑展現(xiàn)出了良好的催化甲醇氧化活性和抗CO毒化能力,從而獲得了廣泛的研究。然而,Ru在高電位發(fā)生溶解、流失等引起的諸多問題會(huì)導(dǎo)致催化劑失活,從而會(huì)降低催化劑的穩(wěn)定性。因此,通過合適的方法來降低PtRu系統(tǒng)中Ru的流失,從而提升催化劑穩(wěn)定性在目前DMFC陽極催化劑的研究中具有重要意義。本論文主要針對(duì)降低Ru流失這一問題,從載體效應(yīng)和組分效應(yīng)等方面,減緩金屬納米顆粒遷移、聚集過程,制備出具有高穩(wěn)定性的DMFC陽極催化劑。主要研究工作如下:一方面,通過對(duì)石墨烯在氨氣中微波進(jìn)行氮摻雜,然后用摻氮石墨烯來負(fù)載PtRu納米顆粒。通過XPS表征發(fā)現(xiàn)負(fù)載鉑釕之后摻氮石墨烯N 1s譜峰負(fù)移了 0.8 eV,這主要是由于Pt,Ru上的電子向碳載體上的含氮基團(tuán)上轉(zhuǎn)移造成的,說明氮摻雜之后提升了 PtRu納米顆粒與載體之間的相互作用。EDS mapping結(jié)果顯示PtRu納米顆粒傾向于在N元素周圍富集而不是在碳上隨機(jī)分布。從TEM的結(jié)果來看,我們?cè)俅伟l(fā)現(xiàn)氮摻雜之后增強(qiáng)了金屬和載體之間的相互作用,因此在加速老化測(cè)試之后,石墨烯負(fù)載鉑釕(PtRu/G)納米催化劑相較于摻氮石墨烯負(fù)載鉑釕(PtRu/NG)納米催化劑表面發(fā)生了更為嚴(yán)重的金屬遷移、聚集的現(xiàn)象。加速老化測(cè)試之后,PtRu/NG,商用PtRu/C和PtRu/G在峰電流密度上的衰減分別為33%,43%和45%,在起始電位上的衰減分別為20 mV,190 mV和210 mV,證明PtRu/NG比商用PtRu/C和PtRu/G具有更好的催化甲醇氧化穩(wěn)定性,尤其是氮摻雜之后明顯降低了催化劑起始電位的衰減,說明氮摻雜能夠明顯降低Ru流失。另一方面,通過浸漬置換的方法在商用PtRu/C中進(jìn)行Au摻雜從而制備PtRuAu/C催化劑,通過調(diào)節(jié)浸漬液中氯金酸的濃度控制Au摻雜的含量。通過對(duì)不同Au摻雜量的PtRuAu/C催化劑進(jìn)行甲醇氧化測(cè)試,并與商用PtRu/C進(jìn)行對(duì)比,發(fā)現(xiàn)微量的Au摻雜并沒有降低商用PtRu/C催化活性,但穩(wěn)定性有顯著提高。XPS表征顯示Au摻雜之后Pt4f和Ru3p譜峰分別正移了 0.3和0.4eV,這主要是由于Pt,Ru的外層電子受到Au元素的吸引、發(fā)生偏移從而增強(qiáng)了金屬之間的相互作用。從TEM的結(jié)果來看,商用PtRu/C在加速老化測(cè)試之后發(fā)生明顯的金屬遷移、聚集的現(xiàn)象,PtRuAu/C-0.5卻并不明顯。加速老化測(cè)試之后,商用PtRu/C峰電流密度衰減了 43%,起始電位衰減了 190 mV,而PtRuAu/C-0.5峰電流密度幾乎沒有發(fā)生衰減,起始電位衰減也僅為10 mV,說明Au摻雜有利于降低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.
【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：O643.36;TM911.4
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本文編號(hào)：1980610