【作者】 杨俊；

【导师】 李洲鹏；

【作者基本信息】 浙江大学 ， 化学工程， 2015， 硕士

【摘要】 燃料电池由于其能量转换率高和对环境友好等优点而受到广泛关注。阴极氧还原反应(ORR)是制约燃料电池发展和推广的重要因素,传统的ORR催化剂使用的是碳担载铂(Pt/C), Pt具有优良的ORR催化活性,但是Pt是贵金属,资源稀少,价格昂贵,限制了燃料电池的产业化发展,因此开发非贵金属催化剂成为了燃料电池的研究热点之一。本文研究了吲哚和吲哚羧酸修饰碳载非贵金属材料作为ORR催化剂,探讨其在酸性和碱性介质中的催化机理,测试其电化学性能,并用于燃料电池,对其性能和稳定性进行验证。本文采用水热法合成复合催化剂材料M-N/C,并首次采用原位透射电镜对催化剂热处理过程中的形貌和结构变化进行分析,采用傅里叶红外光谱(FT-IR)、X射线粉末衍射仪(XRD)、核磁共振光谱(NMR)、电感耦合等离子体发射光谱(ICP)等分析方法对材料进行分析表征；采用循环伏安法(CV)、旋转圆盘法(RDE)等对材料的电化学性能进行测试。通过对催化剂材料的结构成分和在不同介质中的电化学性能进行分析,推测影响催化剂活性的关键因素。研究表明,吲哚修饰碳载钴催化剂(Co-indole/BP)和吲哚羧酸(吲哚甲酸：ICA,吲哚乙酸：IAA,吲哚丙酸：IPA,吲哚丁酸：IBA)修饰碳载钴催化剂都具有良好的ORR催化活性。Co-IAA/BP在酸性和碱性介质中的的催化剂活性明显高于Co-indole/BP。通过原位透射电镜检测到Co-indole/BP 和 Co-IAA/BP在氩气环境下热处理到900℃的过程中(将热处理后的催化剂分别记作Co-indole/BP (900) 和 Co-IAA/BP (900)),有CO3O4晶体形成,Co-indole/BP (900)和Co-IAA/BP (900)在酸性和碱性介质中均具有更高的ORR催化活性。此外,Co-IAA/BP (900)的氧还原初始电位、动力学电流密度和反应转换电子数都明显高于Co-indole/BP (900)。Co-IAA/BP及Co-indole/BP (900) 和 Co-IAA/BP (900)催化剂在酸性介质下也具有良好的ORR催化活性,是因为在Co-IAA和CO3O4中的氧原子具有孤对电子,能够吸引酸性介质中的质子。在酸性介质中,同时含有亲电中心(CO3O4中的Co)和亲核中心(CO3O4中的O)催化活性中心是其具有良好的ORR催化活性的主要原因。在以上研究成果的基础上,通过直接甲醇燃料燃料电池(DMFC)和直接硼氢化钠燃料电池(DBFC)对Co-IAA/BP (900)催化剂进行了实证,在DMFC中,其放电性能比10%Pt/C要差,但是在DBFC中,其放电性能超过了10%Pt/C,说明Co-IAA/BP (900)可以替代10%Pt/C用于直接硼氢化钠燃料电池中。通过阴极寿命测试表明的热处理后的Co-indole/BP 和 Co-IAA/BP都具有良好的稳定性。更多还原

【Abstract】 Fuel cells have attracted much attention due to their high efficiency and environmental friendliness. Oxygen reduction reaction (ORR) in cathode is an important factor that hinders the development of fuel cell. The traditional catalyst of ORR is carbon supported platinum (Pt/C). Pt has excellent catalytic activity. However, the scarcity of Pt in nature is a big problem for its commercial applications. So development of non-precious metal catalysts has become one of the most heated researches in fuel cells. This work has studied the use of indole and indole carboxylic acid modified carbon supported non-precious metal composites as the oxygen reduction reaction catalysts. The study discussed the catalytic mechanism in acidic and alkaline medium,and also test their electrochemical properties and validated their stability in fuel cells.Cobalt coordination compounds with indole and indole carboxylic acid were synthesized using the hydrothermal method. The catalytic cluster formation process during pyrolysis was first investigated through the in-situ transmission electron microscope (TEM) and high resolution TEM observations. Using Fourier infrared spectrum (FT IR), X-ray powder diffraction (XRD), nuclear magnetic resonance spectroscopy (NMR), inductively coupled plasma emission spectrum (ICP) analysis method to analyze material characterization. The catalysts electrochemical properties were tested by cyclic voltammetry (CV) and rotating disk method (RDE), and the key factor that influences the catalytic activity in different medium was also disscussed.Studies had shown that both indole modified carbon supported cobalt catalyst (Co-indole/ BP) and indole carboxylic acid (indole-3-carboxylic acid:ICA, indole-3-acetic acid:IAA, indolyl-3-propionic acid:IPA,3-Indolybutyric acid:IBA) modified carbon supported cobalt catalyst, had good ORR catalytic activity. The Co-IAA/BP exhibited higher oxygen reduction reaction (ORR) current in alkaline electrolyte and more positive ORR potential in acidic electrolyte than the carbon supported Co-indole/BP. Co3O4 crystals were created on the carbon support after pyrolysis of the Co-indole/BP and Co-IAA/BP at 900℃ under Argon atmosphere. The pyrolyzed Co-indole/BP and Co-IAA/BP presented higher ORR current and potential in both acidic and alkaline electrolytes than their origins. Moreover, the ORR on-set potential, kinetic current and electron transfer number of the pyrolyzed Co-IAA/BP were higher than the values of the pyrolyzed Co-indole/BP.Co-IAA/BP and pyrolyzed Co-indole/BP and Co-IAA/BP catalyst in acidic medium had good ORR catalytic activity, because Oxygen in the Co-IAA and Co3O4 draws protons to enhance the ORR occurring in the acidic electrolyte. The formation of the catalytic site composed of electrophilic center coupled with nucleophilic center is the key to develop the ORR catalyst with high electrocatalytic activity in the acidic electrolyte.Based on the study above, a series of fuel cell test had been performed using the synthesized composites as cathode materials. And the results revealed that, pyrolyzed Co-IAA/BP showed worse ORR performance than 10% Pt/C in direct methanol fuel cell (DMFC), But it has better performance compared to 10% Pt/C catalyst in direct sodium borohydride fuel cell(DBFC). Means that the catalyst used for direct sodium borohydride fuel cell can be a replace of 10% Pt/C. The cathode life test showed that the pyrolyzed Co-indole/BP and Co-IAA/BP has good stability.更多还原