本文選題：直接醇類燃料電池　切入點：氧還原反應　出處：《燕山大學》2014年博士論文　論文類型：學位論文

【摘要】：作為一種環(huán)保高效的新能源技術(shù)，直接醇類燃料電池（DMFC）具有啟動和工作溫度低、比功率高、比能量高、工作電流大等特點，是目前最接近大規(guī)模商業(yè)化的燃料電池。DMFC中電極催化劑是該電池裝置的核心部件之一，關系到DMFC的工作效率、使用壽命、制備成本等。炭黑負載鉑基催化劑（Pt/C）是應用最為廣泛的DMFC電極催化劑。但Pt/C的穩(wěn)定性較差，特別是在DMFC陰極的高氧氣濃度、高電勢的環(huán)境中，Pt/C比較容易失去活性。這無疑縮短了DMFC的使用壽命。此外，鉑是一種貴金屬，它的使用增加了DMFC的制造成本。 使用高穩(wěn)定載體材料可以有效提高鉑基催化劑的穩(wěn)定性，而制備高穩(wěn)定性的非鉑催化劑取代鉑基催化劑是降低DMFC制造成本的有效途徑。本文以高穩(wěn)定的納米金剛石（nanodiamond ND）和納米碳化硅（nano-SiC）為基礎材料，，制備新型核殼材料，并將之用于制備高穩(wěn)定的DMFC陰極鉑基以及非鉑催化劑。具體內(nèi)容如下： 1）在高于10-2Pa的真空環(huán)境中，對ND和nano-SiC進行1300-1600C的熱處理，可以使二者表面石墨化，形成表面石墨烯層覆蓋的ND（ND@G）和碳化硅(SiC@G)。因為有高穩(wěn)定性的ND和nano-SiC為核，同時又有高導電性的石墨烯殼層，所以ND@G和SiC@G同時兼具了高穩(wěn)定性和較好的導電性。以二者為載體，制備鉑催化劑（Pt/ND@G和Pt/SiC@G）能夠避免因為載體材料被腐蝕氧化而導致的催化劑失活。通過在0.5mol/L的硫酸（H2SO4）溶液中進行加速老化試驗(ADT)，可以發(fā)現(xiàn)在Pt載量相同時，Pt/ND@G和Pt/SiC@G表現(xiàn)出了遠高于Pt/C的穩(wěn)定性，同時還具有相近甚至略好于Pt/C的陰極氧還原反應（oxygen reduction reaction, ORR）催化活性。 2）利用濃氫氟酸與濃硝酸的混合溶液（體積比1:2），對nano-SiC進行選擇性刻蝕處理，在其表面形成富含含氧官能團的無定型碳層(SiC@O-G)。含氧官能團能夠為納米鉑顆粒提供形核點，進而增加載體與納米鉑顆粒之間的結(jié)合力。這使得納米鉑顆粒的遷移團聚被遏制，加之高穩(wěn)定SiC為核心的支撐作用，SiC@O-G負載的鉑基催化劑的ADT測試結(jié)果也明顯優(yōu)于Pt/C。 3）以ND為原料，分別制備了核殼結(jié)構(gòu)的非鉑催化劑——表層為氮摻雜或鐵、氮共摻的石墨烯，核心為ND的N-ND@G和Fe-N-ND@G。首先對ND@G進行氧化，再將其與三聚氰胺混合，在N2氛中進行熱處理可以獲得N-ND@G；而在ND表面負載納米Fe(OH)3顆粒，將其與三聚氰胺混合，在N2氣氛下保溫850C熱處理3小時，ND在Fe催化劑作用下表面石墨化的同時實現(xiàn)Fe、N摻雜，獲得Fe-N-ND@G。通過電化學實驗，可以發(fā)現(xiàn)N-ND@G和Fe-N-ND@G在堿性條件下，對ORR具有較高的催化活性。在-0.2V（vs. Hg/HgO）高電勢區(qū)域，N-ND@G和Fe-N-ND@G催化的ORR反應電子數(shù)分別達到3.7和3.9，為近四電子反應。其中N-ND@G催化ORR的LSV曲線的半波電位值為-0.12V（vs. Hg/HgO），與載量為20wt%的Pt/C（半波電位-0.052V vs. Hg/HgO）相比僅相差68mV。吡咯型N、吡啶型N和石墨型N間的協(xié)同作用是使N-ND@G具有較高ORR催化活性的主要因素。Fe-N-ND@G的催化ORR的LSV曲線的半波電位值為-0.097V（vs. Hg/HgO），對ORR催化活性要高于N-ND@G，更加接近Pt/C催化劑，這說明Fe與N共摻進一步提高了ORR催化活性。而且N-ND@G和Fe-N-ND@G都具有極高的穩(wěn)定性，是極具潛力的非鉑催化劑。
[Abstract]:As a kind of environmental protection, new energy technology, direct methanol fuel cell (DMFC) has a start and low working temperature, high specific power, high specific energy, working characteristic of the large current, is the electrode catalyst of fuel cell.DMFC is the most close to the large-scale commercial application is one of the core components of the battery device, related to DMFC the work efficiency, service life, cost of preparation. The platinum based catalysts supported on carbon black (Pt/C) is the most widely used DMFC electrode catalyst. But the stability of Pt/C is poor, especially in the high oxygen concentration of DMFC cathode, high potential environment, Pt/C is easy to lose activity. This will reduce the DMFC service life. In addition, platinum is a precious metal, its use has increased the production cost of the DMFC.
The use of high stable carrier material can effectively improve the stability of platinum based catalysts, and non platinum catalysts with high stability to replace platinum based catalysts is an effective way to reduce the manufacturing cost of DMFC. The high stability of nano diamond (nanodiamond ND) and nanometer silicon carbide (nano-SiC) as basic material, preparation of novel core-shell materials. And used the DMFC cathode platinum based preparation of high stable and non platinum catalyst. The specific contents are as follows:
1) in a vacuum environment is higher than that of 10-2Pa, ND and 1300-1600C on heat treatment of nano-SiC, can make the two graphite surface, formed on the surface of graphene layer covered ND (ND@G) and silicon carbide (SiC@G). Because of the high stability of ND and nano-SiC as the core, and has the high conductivity of graphene shell electric, so ND@G and SiC@G are both high stability and good conductivity. In two as the carrier, the preparation of platinum catalysts (Pt/ND@G and Pt/SiC@G) can avoid the catalyst carrier material is caused by corrosion oxidation inactivation. The sulfur acid 0.5mol/L (H2SO4) solution for accelerated aging test (ADT), can be found in the same Pt load, Pt/ND@G and Pt/SiC@G showed stability is much higher than that of Pt/C, but also has similar or even slightly better than the cathodic oxygen reduction reaction of Pt/C (oxygen reduction reaction, ORR) catalytic activity.
2) using a mixed solution of concentrated hydrofluoric acid and nitric acid (volume ratio 1:2), nano-SiC selective etching process, the formation of amorphous carbon layer rich in oxygen-containing functional groups on the surface (SiC@O-G). Oxygen containing functional groups can provide nucleation sites for platinum nanoparticles, and further increasing the binding force between the body and the loading of platinum nanoparticles this makes the migration of particles. The platinum nanoparticles agglomeration were checked, and support the role of high stable SiC as the core, the ADT test results of platinum based catalysts supported on SiC@O-G is obviously superior to that of Pt/C.
3) using ND as the raw material were prepared by the non - platinum catalyst surface core-shell structure for nitrogen doped graphene or iron, nitrogen doped, ND N-ND@G and Fe-N-ND@G. as the core of the first oxidation of ND@G, and then mixed with melamine, heat treatment in N2 atmosphere of N-ND@G can be obtained; while on the surface of ND nano Fe (OH) 3 particles with the mixture of melamine, under N2 atmosphere heat preservation heat treatment of 850C for 3 hours, at the same time, the realization of Fe, ND in Fe under the effect of catalyst surface graphitization of N doped Fe-N-ND@G. by electrochemical experiments, can be found in N-ND@ G and Fe-N-ND@G in alkaline condition. The high catalytic activity of ORR. -0.2V (vs. Hg/HgO) in the high potential region, ORR reaction catalyzed by Fe-N-ND@G and N-ND@G electron number reached 3.7 and 3.9, nearly four electron reaction. The half wave potential of LSV curve of N-ND@G catalyzed by ORR as the value of the -0.12V (vs. Hg/HgO), and Load is 20wt% (Pt/C -0.052V vs. Hg/HgO half wave potential) compared to a difference of only 68mV. pyrrole type N, synergistic effect of pyridine type N and type N graphite is the half wave potential of LSV curve of ORR.Fe-N-ND@G catalytic main factors in the N-ND@G has a high catalytic activity of ORR the value of -0.097V (vs. Hg/HgO), the the catalytic activity of ORR is higher than N-ND@G, more close to the Pt/C catalyst, which shows that Fe and N Co doped to further improve the catalytic activity of ORR. And has high stability of N-ND@G and Fe-N-ND@G, is a non platinum catalyst potential.

【學位授予單位】：燕山大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：O643.36;TM911.4

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