碳载过渡金属氨基比林类催化剂在碱性介质中的氧还原性特性及机制研究

发布时间：2018-04-19 23:14

本文选题：燃料电池 + 氧还原反应　；参考：《东华大学》2015年硕士论文

【摘要】：人类正面临能源危机和环境污染问题，聚合物电解质膜燃料电池具有能量转换效率高和零污染两项重要优势，长远来看其具有替代内燃机成为新型动力源的发展潜力。由于目前燃料电池阴极氧还原催化剂仍需采用贵金属Pt，成本问题成为制约燃料电池商业化应用的关键因素。因此制备可替代Pt系催化剂的新型非贵金属催化剂成为燃料电池发展的突破口，其中碳载氮掺杂催化剂表现出最高的氧还原活性和稳定性，受到研究者的广泛青睐。本论文以商业炭黑BP2000为载体，含氮有机物氨基比林为氮源，以多种过渡金属盐为金属前躯体制备了一系列碳载金属氨基比林催化剂（M-Apyr/C）作为研究对象，通过循环扫描伏安法（CV）、线性扫描伏安（LSV）、旋转环盘电极技术（RRDE）等电化学测试手段对这些催化剂在碱性介质中的氧还原催化活性和电极动力学进行了详尽研究。在此基础上结合X射线衍射（XRD）、透射电子显微镜（TEM）、X射线光电子能谱（XPS）等物理表征方法分析了促进或抑制氧还原活性及选择性的各种因素，从而进一步揭示M-Apyr/C催化剂氧还原活性的作用机制。首先，通过对比碳载体种类对M-Apyr/C氧还原活性的影响，，选择BP2000作为碳载体；通过碳载体组分优化，得到载体在整个催化剂中所占的质量比为60%时制得催化剂氧还原活性最高；通过金属载量优化，得到金属载量为5%时制得催化剂氧还原活性最高；通过未经解热及不同温度热解后催化剂活性比对，得到M-Apyr/C催化剂的最佳热解温度为700℃。其次，分析了无金属催化剂C-Metal free，及采用Mn、Fe、Co、Ni、Cu五种金属掺杂的C-Mn、C-Fe、C-Co、C-Ni、C-Cu催化剂。得到金属添加对于催化剂氧还原性能的提升顺序为Co Fe~CuMn Ni，对催化选择性的提升顺序为Fe Mn Co Cu Ni。结合XRD、TEM、XPS分析得出以下四点结论：（ⅰ）五种金属热解过程中与硫结合的程度排序为Mn、Fe Co Ni、Cu；（ⅱ）热解过程中N、S在与金属元素结合时存在竞争机制，金属与S结合会阻碍其与N的结合；（ⅲ）催化剂表面金属元素的分散、分布状态，以及金属与载体结合程度对催化活性产生重要影响；（ⅳ）金属及吡啶氮形成的M-Nx/C结构是构成M-Apyr/C催化剂的活性中心位结构。随后中选用催化选择性最高的Fe和氧还原活性最高的Co作为目标金属，分别研究Fe-Apyr/C及Co-Apyr/C的阴离子掺杂效应。对于所制备研究的四种Fe-Apyr/C催化剂，氧还原催化活性由高到低遵循C-Fe(NO3)3 C-FeAc C-FeSO4 C-FeCl2的规律，催化选择性排列为C-FeAc C-Fe(NO3)3 C-FeSO4 C-FeCl2。对于所制备的三种Co-Apyr/C催化剂，氧还原活性和选择性均遵循C-Co(NO3)2C-CoSO4~C-CoCl2的规律。对于不同种阴离子对催化剂表面结构、催化活性及选择性的影响主要得出两点结论：（ⅰ）NO3-离子能够促进金属在催化剂表面的分散以及金属与载体和氮源的结合，进而促进M-Nx/C活性结构的形成，提高M-Apyr/C催化剂催化氧还原活性及选择性。（ⅱ）SO42-离子掺杂会导致热解过程的N、S竞争作用，抑制M-Nx/C活性结构的形成，从而造成M-Apyr/C催化剂氧还原活性的下降。最后以C-Co(NO3)2为目标催化剂，研究了其半电池氧还原反应的载量效应，结果表明，400μg/cm2载量下电极氧还原活性最高，600μg/cm2载量下催化剂的选择性最高。经循环伏安10000圈加速老化测试后，催化剂性能仅下降31mV，表明C-Co(NO3)2具有优良的耐久稳定性。进一步制备膜电极（MEA）进行单电池测试表明：以C-Co(NO3)2催化剂作为阴极所制备MEA碱性条件室温下的发电功率为36.5mW/cm2，接近本实验室在相同发电条件下得到的商业铂碳催化剂发电功率。
[Abstract]:Human beings are facing the problems of energy crisis and environmental pollution. Polymer electrolyte membrane fuel cells have two important advantages, such as high energy conversion efficiency and zero pollution. In the long run, it has the potential to replace the internal combustion engine to become a new power source. Because of the current fuel cell cathode oxygen and the original catalyst still need to use the precious metal Pt, the cost problem As a key factor restricting the commercial application of fuel cells, a new non noble metal catalyst, which can replace the Pt catalyst, has become the breakthrough point of the development of fuel cell. Carbon carrying nitrogen doping catalyst shows the highest activity and stability of oxygen reduction, which is widely favored by researchers.
In this paper, a series of carbon loaded amino pyrine catalysts (M-Apyr/C) were prepared by using commercial carbon black BP2000 as the carrier and nitrogen organic substance amino billing as the nitrogen source. A series of carbon borne amino pyrine catalysts (CV), linear sweep voltammetry (LSV), rotating ring disk electrode technology (RRDE) and other electrochemical methods were used as the metal precursors. The catalytic activity and electrode kinetics of these catalysts in alkaline medium were studied in detail. On this basis, various factors, such as X ray diffraction (XRD), transmission electron microscope (TEM), X ray photoelectron spectroscopy (XPS) and other physical characterization methods, were used to analyze the factors of promoting or inhibiting the activity and selectivity of oxygen reduction. The mechanism of oxygen reduction activity of M-Apyr/C catalyst was further revealed.
First, by comparing the effect of the type of carbon carrier on the M-Apyr/C oxygen reduction activity, BP2000 is selected as the carbon carrier, and the catalyst oxygen redox activity is the highest when the mass ratio of the carrier in the whole catalyst is 60%, and the catalyst oxygen is obtained when the metal load is 5% through the optimization of the carbon carrier component. The activity of M-Apyr/C catalyst is the highest, and the optimum pyrolysis temperature of the catalyst is 700 C by comparing the catalyst activity without pyrolysis and pyrolysis at different temperatures.
Secondly, the five metals doped Mn, Fe, Co, Ni, Cu are used for the five metals doped C-Mn, C-Fe, C-Co, C-Ni, and C-Cu catalysts. The order of promotions for the catalyst oxygen reduction is obtained, and the following four points are obtained. Conclusion: the degree of sulfur binding with sulfur in the five metal pyrolysis processes is Mn, Fe Co Ni, Cu; (II) N, S has a competitive mechanism in the process of binding with metal elements during the pyrolysis process, and the combination of metal and S hinders its combination with N; (III) the dispersion and distribution of metal elements on the surface of the catalyst and the combination of metal and carrier to catalysis The M-Nx/C structure formed by metal and pyridine nitrogen is the active center structure of M-Apyr/C catalyst.
Subsequently, the highest selective Fe and Co with the highest oxygen reduction activity were selected as target metals, and the anion doping effects of Fe-Apyr/C and Co-Apyr/C were studied respectively. For the four Fe-Apyr/C catalysts studied, the catalytic activity of oxygen reduction from high to low followed C-Fe (NO3) 3 C-FeAc C-FeSO4 C-FeCl2 and catalyzed selective arrangement. For the three Co-Apyr/C catalysts prepared by C-FeAc C-Fe (NO3) 3 C-FeSO4 C-FeCl2., the activity and selectivity of oxygen reduction follow the law of C-Co (NO3) 2C-CoSO4~C-CoCl2. The effects of different kinds of anions on the surface structure, catalytic activity and selectivity of the catalyst are mainly concluded: NO3- ions can promote metal to be promoted. The dispersion of chemical agent surface and the combination of metal with carrier and nitrogen source promote the formation of M-Nx/C active structure and increase the activity and selectivity of M-Apyr/C catalyst to catalyze oxygen reduction. (II) the doping of SO42- ions leads to the N, S competitive action of the pyrolysis process and the inhibition of the formation of M-Nx/C active structure, resulting in the oxygen reduction activity of the M-Apyr/C catalyst. The decline.
At last, C-Co (NO3) 2 was used as the target catalyst to study the load effect of the oxygen reduction reaction in the semi battery. The results showed that the oxygen reduction activity of the electrode was the highest under the 400 g/cm2 load, and the selectivity of the catalyst under the load of 600 mu g/cm2 was the highest. The performance of the catalyst decreased by 31mV after the accelerated aging test of 10000 cycles of cyclic voltammetry, indicating that C-Co (NO3) 2 had excellent performance. The single cell test of the further preparation of membrane electrode (MEA) shows that the power generation power of C-Co (NO3) 2 catalyst as cathode at room temperature is 36.5mW/cm2, which is close to the power generation of commercial platinum carbon catalyst obtained under the same power generation condition.

【学位授予单位】：东华大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O643.36;TM911.4

【共引文献】