本文關(guān)鍵詞： 碳基 納米 包裹 催化劑 構(gòu)建 及其 抗醇 還原 催化 性能 研究　出處：《南京大學》2016年碩士論文　論文類型：學位論文

【摘要】：直接甲醇燃料電池(DMFC)具有能量轉(zhuǎn)換效率高、環(huán)境友好、低溫啟動速度快、燃料甲醇易輸運且來源廣泛、電池結(jié)構(gòu)簡單等優(yōu)點,在便攜式電源等方面有廣闊應(yīng)用前景,因而備受關(guān)注。其核心是高性能的電催化劑,到目前為止,最常用的Pt/C催化劑的活性高,但存在穩(wěn)定性差、抗CO中毒能力低等不足。就陰極氧還原(ORR)而言,還存在抗醇能力差的不足,因此,開發(fā)催化活性高、抗CO中毒和抗醇能力強、穩(wěn)定性好的Pt基催化劑尤顯重要。人們發(fā)展了Pt單原子化、合金化和包裹這三種策略提高其抗醇性能。我們課題組開發(fā)出了具有高比表面積、微孔-介孔-大孔共存、高導電性等特征的空心碳基納米籠。利用其約0.6 nm的微孔和空心納米籠狀結(jié)構(gòu)特征,本論文圍繞碳基納米籠包裹鉑催化劑的設(shè)計、可控合成及抗醇ORR性能開展了較為系統(tǒng)深入的研究工作,主要進展包括：1.可控地制備出碳基納米籠包裹或負載的鉑催化劑：以具有三維分級結(jié)構(gòu)的堿式碳酸鎂為前驅(qū)物,苯或吡啶為碳源,制備出具有高比表面積、高導電性、微孔-介孔-大孔共存等特征的三維分級結(jié)構(gòu)碳納米籠(CNC)和氮摻雜CNC(NCNC)。利用簡單的真空-填充方法,將約1.3 nm的Pt粒子填裝到CNC和NCNC的納米空腔內(nèi),可控地制備出具有包裹結(jié)構(gòu)的Pt@CNC與Pt@NCNC催化劑。借助微波輔助乙二醇還原法,將約2.6 nm的Pt粒子負載在CNC和NCNC的納米籠外表面,可控地制備出負載型的Pt/CNC與Pt/NCNC對照組催化劑。2. Pt@CNC 與 Pt@NCNC具有優(yōu)異的ORR活性、穩(wěn)定性和抗醇性能：Pt@CNC與Pt@NCNC均展現(xiàn)出了良好的ORR活性,如Pt@NCNC的起始電位為650mV (vs.Ag/AgCl),略低于對照組Pt/NCNC和商業(yè)Pt/C的680 mV；二者均表現(xiàn)出完全的抗醇性能,而Pt/C和對照組催化劑完全不抗醇；二者均表現(xiàn)出遠優(yōu)于Pt/C和對照組催化劑的ORR穩(wěn)定性。通過CO2擴孔和再沉積碳層封孔的方法調(diào)變納米籠壁上微孔的尺寸和數(shù)量,發(fā)現(xiàn)：當微孔尺寸變大時,Pt@NCNC的ORR性能提高而抗醇性能劣化；當微孔尺寸和數(shù)量減小,其ORR性能呈下降趨勢,最終與NCNC載體的ORR性能相當�？梢�,微孔對Pt@NCNC催化劑的電化學性能起關(guān)鍵作用。換句話說,納米籠壁上的約0.6nm的微孔具有分子篩分效應(yīng),允許尺寸相對較小的氧分子和離子通過籠壁進入納米空腔,而阻礙大尺寸的分子如醇穿過微孔進入籠內(nèi)。這為開發(fā)新穎的抗醇的Pt基ORR電催化劑提供思路。3.原位合成Pt@NCNC催化劑及其ORR性能：通過微波輔助乙二醇還原法將Pt納米粒子負載在納米MgO粒子表面,浸漬醋酸鎂后熱解形成新的MgO層,以吡啶為碳源,得到包裹型Pt@NCNC催化劑。初步的結(jié)果表明,在酸性介質(zhì)中,其具有完全的抗醇性能,但ORR性能不夠好。通過優(yōu)化制備條件,有望開發(fā)出高性能的抗醇的Pt基ORR電催化劑。
[Abstract]:Direct methanol fuel cell (DMFC) has the advantages of high efficiency of energy conversion, friendly environment, fast start-up speed at low temperature, easy transportation of fuel methanol from a wide range of sources, simple structure of the battery, and so on. It has a broad application prospect in portable power supply and so on. The core of the catalyst is high performance electrocatalyst. By far, the most commonly used Pt/C catalyst has high activity, but its stability is poor, and its ability to resist CO poisoning is low. Therefore, it is very important to develop Pt catalyst with high catalytic activity, strong ability to resist CO poisoning and alcohol, and good stability. Alloying and encapsulation are three strategies to improve their alcohol resistance. Our team has developed a high specific surface area, micropore-mesoporous and macroporous coexistence. Hollow carbon based nano-cages with high electrical conductivity and so on. Based on its 0.6 nm micropore and hollow nano-cage structure, this paper focuses on the design of carbon based nano-cages coated with platinum catalysts. Systematic and in-depth research work has been carried out on the properties of controllable synthesis and alcohol-resistant ORR. The main progress includes: 1. Controllable preparation of carbon based nano-cage encapsulated or supported platinum catalysts: the basic magnesium carbonate with a three-dimensional hierarchical structure is used as the precursor. Using benzene or pyridine as carbon source, three dimensional graded structure carbon nanocage (CNC) and nitrogen-doped CNC (NCNC) with high specific surface area, high conductivity and coexistence of micropore-mesoporous and macroporous were prepared. The Pt particles of about 1.3 nm were filled into the nano-cavity of CNC and NCNC, and the Pt@CNC and Pt@NCNC catalysts with encapsulated structure were prepared under controlled control. By microwave-assisted ethylene glycol reduction, the Pt particles of about 2.6nm were loaded on the outer surfaces of CNC and NCNC nanometers. The supported catalysts of Pt/CNC and Pt/NCNC were prepared under controlled control. 2.The catalysts of Pt@CNC and Pt@NCNC showed excellent ORR activity, stability and anti-alcohol-resistant properties. Both Pt@CNC and Pt@NCNC exhibited good ORR activity. For example, the initial potential of Pt@NCNC was 650mV / v / AgAgClN, which was slightly lower than that of Pt/NCNC and commercial Pt/C (680mV), both of which showed complete alcohol-resistance, but Pt/C and control catalyst were not resistant to alcohols at all. Both of them showed much better ORR stability than Pt/C and the control catalyst. The size and number of micropores on the wall of the nanocage were adjusted by means of CO2 pore expansion and redeposited carbon layer sealing. It was found that when the size of micropore became larger, the ORR performance of PTN NCNC improved and its anti-alcohol performance deteriorated, and when the size and number of micropores decreased, the ORR performance showed a downward trend, and finally the ORR performance of NCNC carrier was similar to that of NCNC carrier. Micropores play a key role in the electrochemical performance of Pt@NCNC catalysts. In other words, about 0.6 nm micropores on the wall of nanospheres have molecular sieve separation effects, allowing relatively small oxygen molecules and ions to enter the nano-cavity through the cage wall. This provides a way to develop novel Pt based ORR electrocatalysts for alcohol resistance. 3. In situ synthesis of Pt@NCNC catalyst and its ORR performance: microwave assisted ethylene glycol reduction method to Pt. Nanoparticles are loaded on the surface of nanometer MgO particles. After impregnating magnesium acetate, a new MgO layer was formed, and the encapsulated Pt@NCNC catalyst was obtained by using pyridine as carbon source. The preliminary results showed that it had complete alcohol-resistant property in acid medium, but the ORR performance was not good enough. It is expected to develop high performance Pt-based ORR electrocatalyst for alcohol resistance.
【學位授予單位】：南京大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：O643.36

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