本文選題：質(zhì)子交換膜燃料電池　切入點(diǎn)：磁控濺射　出處：《南京大學(xué)》2017年碩士論文

【摘要】：現(xiàn)如今,Pt/C催化劑依舊是質(zhì)子交換膜燃料電池中應(yīng)用最為普遍的催化劑,但由于Pt資源儲(chǔ)量有限、價(jià)格昂貴,因而增加了燃料電池的成本。為了推動(dòng)燃料電池商業(yè)化的進(jìn)程,必須改進(jìn)催化劑的制作方法或改變催化劑的結(jié)構(gòu),來(lái)提高Pt的利用率、降低催化劑中Pt的載量。目前,Pt/C催化劑的制作方法主要有浸漬法、膠體法和微乳液法等,但這些方法的步驟都較為繁瑣,將催化劑分散在擴(kuò)散層或質(zhì)子交換膜上時(shí),也易導(dǎo)致分散不均,而且單用Pt作為催化劑,存在活性較低且易中毒的問題。磁控濺射法是一種操作較為簡(jiǎn)便的物理方法,在低壓氬氣氛圍中,磁場(chǎng)與電場(chǎng)交互作用下,氬離子撞擊靶材,使濺射粒子均勻分散在基底上,提高了催化劑的均勻性,間接降低了催化層的厚度。本論文利用磁控濺射的方法,首先將還原氧化石墨烯層覆蓋的碳紙作為基底,在其表面直流濺射Pt,利用還原氧化石墨烯的高致密性阻止Pt的掉落,從而提高Pt的利用率;其次將擴(kuò)散層作為基底,在其表面分別直流濺射Pt、雙靶共濺射Pt與Co,利用Co對(duì)Pt活性的激發(fā),從而降低Pt的載量。具體研究工作如下:首先,我們將氧化石墨懸濁液涂布在碳紙上,在氫氬混合氣體氛圍中進(jìn)行熱還原后,將鉑用直流濺射法沉積在還原氧化石墨烯上,制備出一種結(jié)構(gòu)優(yōu)化的氣體擴(kuò)散電極。我們考察了氧化石墨溶液濃度及還原溫度對(duì)還原氧化石墨烯的覆蓋率及還原程度的影響,并研究了濺射時(shí)氣體流量及厚度對(duì)氣體擴(kuò)散電極的形貌及性能的影響。結(jié)果表明,濃度為1 mg·ml-1的氧化石墨溶液,具有最佳的覆蓋率,而且還原溫度越高,還原氧化石墨烯中氧含量越少,氧化石墨還原程度越高;隨著濺射厚度的增加,Pt薄膜表面會(huì)出現(xiàn)明顯的凸起和溝壑形貌,氣體流量30 scm,厚度為10 nm的Pt膜具有最佳的單電池功率密度175.6 mW·cm-2,最高的電化學(xué)活性面積65.4 m2·g-1。從上述結(jié)果發(fā)現(xiàn),還原氧化石墨烯能夠有效阻擋Pt落入碳紙中;Pt薄膜表面的凸起形貌有利于提高Pt的活性面積,適當(dāng)?shù)臍怏w流量與厚度能夠使其達(dá)到峰值,使催化劑發(fā)揮出最佳的催化活性。為了降低催化劑中Pt的用量,我們首先將Pt用直流濺射法直接濺射在擴(kuò)散層上,調(diào)整濺射厚度,測(cè)試其作為陰極氣體擴(kuò)散電極的質(zhì)子交換膜燃料電池極化曲線。結(jié)果表明,單濺射鉑而不使用碳載體,電池性能依舊表現(xiàn)良好。在濺射厚度80 nm時(shí),鉑載量0.20 mg·cm-2,最大功率密度可達(dá)691.7 mW·cm-2。然后,我們采用雙靶共濺的方法,將Pt用直流濺射、Co用射頻濺射,同時(shí)分散在擴(kuò)散層上,在氫氬混合氣中進(jìn)行熱處理后,測(cè)試其單電池性能。結(jié)果表明,同樣厚度的催化層,雙靶共濺射Pt與Co與單一直流濺射Pt的單電池性能相差并不明顯。從上述結(jié)果發(fā)現(xiàn),高溫處理,使Co與Pt形成合金結(jié)構(gòu),Co的加入,提高了 Pt的催化活性,在性能得以保持的前提下,Pt載量得到明顯下降。
[Abstract]:Today Pt- / C catalyst is still the most widely used catalyst in proton exchange membrane fuel cell (PEMFC), but the cost of fuel cell is increased because of the limited Pt resource and high price.In order to promote the commercialization of fuel cells, it is necessary to improve the preparation method of the catalyst or to change the structure of the catalyst to increase the utilization of Pt and reduce the Pt loading in the catalyst.At present, the preparation methods of Pt- / C catalyst are mainly impregnation, colloid and microemulsion methods, but the steps of these methods are complicated, when the catalyst is dispersed on the diffusion layer or the proton exchange membrane, it is also easy to lead to uneven dispersion.Moreover, using Pt as catalyst alone has the problem of low activity and easy poisoning.The magnetron sputtering method is a simple physical method. Under the interaction of magnetic field and electric field in low pressure argon atmosphere, argon ions impact on the target, which makes the sputtering particles dispersed uniformly on the substrate and improves the uniformity of the catalyst.The thickness of the catalyst layer is reduced indirectly.In this paper, the carbon paper coated with reduced graphene layer was first used as the substrate by magnetron sputtering, and the Pt was deposited on the surface by DC sputtering. The high density of reduced graphene was used to prevent the Pt from falling and the utilization rate of Pt was improved.Secondly, the diffusion layer was used as the substrate, and the Pt and Coon were co-sputtering on the surface of the diffusion layer respectively. The Pt activity was excited by Co, thus the loading of Pt was reduced.The specific research work is as follows: firstly, we coated graphite oxide suspension on carbon paper, then deposited platinum on reduced graphene by direct current sputtering after thermal reduction in the mixed gas atmosphere of hydrogen and argon.A gas diffusion electrode with optimized structure was prepared.The effects of the concentration of graphite oxide solution and reduction temperature on the coverage and reduction degree of reduced graphene were investigated. The effects of gas flow rate and thickness on the morphology and properties of gas diffusion electrode during sputtering were studied.The results showed that the graphite oxide solution with concentration of 1 mg ml-1 had the best coverage, and the higher the reduction temperature, the less the oxygen content in the reduced graphene and the higher the degree of reduction of graphite oxide.With the increase of sputtering thickness, the surface of Pt thin film has obvious protruding and gully morphology. The Pt film with the gas flow rate of 30 scm, the thickness of 10 nm Pt film has the best single cell power density of 175.6 MW cm-2, and the highest electrochemical active area is 65.4 m2 g-1.From the above results, it is found that the reduced graphene oxide can effectively block Pt from falling into carbon paper and the protruding morphology of Pt film surface is beneficial to increase the active area of Pt, and the proper gas flow rate and thickness can make it reach its peak value.The catalyst has the best catalytic activity.In order to reduce the amount of Pt in the catalyst, we first directly sputtering Pt onto the diffusion layer by DC sputtering, adjusting the sputtering thickness, and measuring the polarization curve of PEMFC as cathode gas diffusion electrode.The results show that the performance of the battery is still good without carbon carrier.When the sputtering thickness is 80 nm, the platinum loading is 0.20 mg / cm ~ (-2) and the maximum power density is 691.7 MW / cm ~ (-2).Then, by using the method of double target co-splashing, the single cell performance was tested after the Pt was sputtered by DC sputtering with RF sputtering and dispersed on the diffusion layer after heat treatment in the mixture of hydrogen and argon.The results show that there is no significant difference in the performance of Pt and Co with single DC sputtering Pt with the same thickness of catalyst layer.From the above results, it is found that the addition of Co into Pt alloy structure after high temperature treatment improves the catalytic activity of Pt, and decreases the Pt load obviously under the condition of keeping the performance of Pt.
【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)】：TM911.4
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本文編號(hào)：1729179