直接甲醇燃料电池非铂催化剂的制备及其性能研究

发布时间：2018-05-15 01:40

本文选题：直接甲醇燃料电池 + 阳极催化剂　；参考：《太原理工大学》2015年硕士论文

【摘要】：随着人类社会的进步，人们对能源和环境问题有了更深入的认识，环保新能源已成为世界各国能源发展战略的核心。直接甲醇燃料电池（DMFC）因具有高效、低污染、燃料易获取储存和运输等优势而成为开发与研究的热点，可广泛应用于汽车、飞机、航天、航海等领域。但在燃料电池的实际应用中电池成本过高，能量转化效率偏低等问题一直困扰着燃料电池的商业化运用。其根本原因则在于现有条件下电催化剂价格昂贵且效率不高，因此研制廉价高效催化剂具有重要意义。本论文采用钯、银等金属盐作为前驱化合物，通过PVP保护的方法将相应金属负载于Vulcan XC-72活性碳表面，制备负载型的纳米催化剂以达到提高金属的反应接触面积从而提高单位质量金属的利用效率并降低成本。首先，采用以XC-72活性炭为载体,用碱（NaOH、氨水）调节溶液的酸碱性，用NaBH4作还原剂制备Pd/C催化剂，筛选制作催化剂的最佳配方。通过透射电镜（TEM）,X-射线衍射（XRD）及原子吸收光谱法（AAS），对催化剂的结构、形貌及金属的实际负载量进行表征，并通过循环伏安法（CV）测试其电化学活性，从不同角度分析比较Pd/C催化剂的活性。结果显示，碱的添加对提高了钯的负载量，而弱碱氨水的效果要优于强碱氢氧化钠；而在相同体系下，3ml氨水为最佳使用量。测试结果还显示，氨水的添加不但提高了金属钯的负载量，还改善了金属钯纳米颗粒的分散程度及其粒径，其中以3ml氨水条件下的催化剂金属颗粒最小，分散程度最均匀。在添加3ml氨水的条件下，发现不同的还原剂添加量也会影响到钯的粒径及分散程度。实验表明，在其他条件相同的情况下，投加160倍硼氢化钠所制备的催化剂显示了最好的性能。最后得出，在该实验条件下的催化剂的最佳配方为，在反应溶液为200ml的条件下，，加入PVP1,252g，PdCl20.02g，160倍硼氢化钠，3ml1mol/L氨水。此外，本论文还研究了炭载银催化剂的制备及其电催化活性。由于银在元素周期表中与钯同周期并在相邻主族，故与钯具有相似性。更为重要的是银与钯相比具有极大的价格优势，因此对于Ag作为阳极催化性能的研究是非常有必要的。本研究分别采用加40倍、80倍、160倍硼氢化钠制备Ag/C催化剂，通过透射电镜（TEM）,X-射线衍射（XRD）及原子吸收光谱法（AAS），对催化剂的结构、形貌及金属的实际负载量进行表征，并通过循环伏安法（CV）测试其电化学活性，从不同角度分析比较Ag/C催化剂的活性。研究结果表明，随着加入还原剂量的增加。催化活性逐渐升高。研究还发现，加入不同量的还原剂并未影响催化剂的负载量，而影响到了金属颗粒的大小和分散性。结果表明在160倍硼氢化钠条件下制备的Ag/C催化剂中银纳米粒子粒径均匀，分散性较好，电化学性最高。但是，相比单金属钯纳米催化剂，银的粒径较大导致其催化活性不如Pd/C催化剂。关于Pd/C和Ag/C催化剂的研究中发现，Pd与Ag的催化特征各有千秋。若综合两者优势，有可能会获得更为理想的催化剂。为此本论文在此前的研究基础上以Vulcan XC-72为载体通过溶胶法制备了炭载Pd-Ag双金属纳米催化剂。加入NaOH调节溶液的酸碱性，并通过改变硼氢化钠的添加量控制晶体生长。本研究分别在40倍、80倍、160倍硼氢化钠条件下制备Pd-Ag/C催化剂样品，通过透射电镜（TEM）,X-射线衍射（XRD）及原子吸收光谱法（AAS），对催化剂的结构、形貌及金属的实际负载量进行表征，并通过循环伏安法（CV）测试其电化学活性，从不同角度分析比较Pd-Ag/C催化剂的活性。研究结果显示，在80倍硼氢化钠的条件下制备的催化剂不但具有良好的催化性能，且抗中毒性能良好。文末结合本论文中制备催化剂所存在的问题，对未来的研究工作提出了合理的建议。本论文述及的制备炭载型纳米催化剂的方法具有广泛的适用性，将对其它的纳米催化剂制备产生深远的影响。
[Abstract]:With the progress of human society, people have a deeper understanding of energy and environmental problems. New environmental protection energy has become the core of the energy development strategy of all countries in the world. Direct methanol fuel cell (DMFC) has become a hot spot for development and research because of its advantages such as high efficiency, low pollution, easy access to storage and transportation of fuel. However, in the practical application of fuel cells, the high cost of battery and low efficiency of energy conversion have plagued the commercialization of fuel cells. The fundamental reason is the high cost and low efficiency of the electrocatalyst under the existing conditions. Therefore, it is of great significance to develop a cheap and efficient catalyst. In this paper, the metal salts such as palladium, silver and other metal salts are used as precursors. By means of PVP protection, the corresponding metal is loaded on the surface of Vulcan XC-72 active carbon to prepare the supported nano catalyst to increase the contact area of the metal and improve the efficiency of the unit mass metal and reduce the cost.
First, using XC-72 active carbon as the carrier, using alkali (NaOH, ammonia water) to adjust the acidity and alkalinity of the solution, using NaBH4 as the reducing agent to prepare the Pd/C catalyst and screening the best formula for making the catalyst. Through the transmission electron microscope (TEM), X- ray diffraction (XRD) and atomic absorption spectrometry (AAS), the structure, morphology and the actual load of the metal are made out by the transmission electron microscope (TEM). The electrochemical activity was tested by cyclic voltammetry (CV) and the activity of Pd/C catalyst was analyzed and compared from different angles. The results showed that the addition of alkali increased the load of palladium, while the effect of weak alkali ammonia water was better than that of alkali sodium hydroxide; and under the same system, the 3ml ammonia was the best use. The test results also showed that the ammonia water was added. Addition not only improves the load of metal palladium, but also improves the dispersing degree and particle size of metal palladium nanoparticles, in which the catalyst metal particles are the smallest and the dispersion degree is the most uniform under the condition of 3ml ammonia water. Under the condition of adding 3ml ammonia water, it is found that the addition of different reductants also affects the particle size and dispersion of palladium. In the case of the same other conditions, the catalyst prepared by adding 160 times the sodium borohydride showed the best performance. Finally, the best formula of the catalyst under the experimental condition was that, under the condition of the reaction solution of 200ml, PVP1252g, PdCl20.02g, sodium borohydride and 3ml1mol/L ammonia water were added.
In addition, the preparation and electrocatalytic activity of the carbon loaded silver catalyst are also studied. Because silver is in the same periodic table with palladium in the periodic table and is adjacent to the host, it is similar to palladium. It is more important that silver has a great price advantage compared with palladium. Therefore, it is necessary to study the catalytic performance of Ag as a anode. The Ag/C catalyst was prepared by adding 40 times, 80 times and 160 times sodium borohydride. The structure, morphology and the actual load of metal were characterized by transmission electron microscopy (TEM), X- ray diffraction (XRD) and atomic absorption spectrometry (AAS). The electrochemical activity of the catalyst was tested by cyclic voltammetry (CV), and Ag/C was compared from different angles. The results showed that the catalytic activity increased gradually with the increase of the reduced dose. It was also found that the amount and dispersion of the metal particles were affected by the addition of different reductants, and the size and dispersion of the metal particles were affected. The results showed that the silver nanoparticles were prepared in the Ag/C catalyst prepared at 160 times of sodium borohydride. The particle size is uniform, the dispersity is better, and the electrochemical property is the highest. However, compared with the single metal palladium nano catalyst, the larger particle size of silver leads to its less catalytic activity than the Pd/C catalyst.
In the study of Pd/C and Ag/C catalysts, it is found that the catalytic characteristics of Pd and Ag have different characteristics. If the two advantages are comprehensive, it is possible to obtain more ideal catalysts. Therefore, on the basis of this study, a carbon loaded Pd-Ag bimetallic nano catalyst was prepared on the basis of Vulcan XC-72 as the carrier, and NaOH to adjust the acid of the solution by adding NaOH. The crystal growth was controlled by the addition of sodium borohydride. The Pd-Ag/C catalyst samples were prepared under the conditions of 40 times, 80 times and 160 times sodium borohydride. The structure, morphology and actual load of the metal were characterized by transmission electron microscopy (TEM), X- ray diffraction (XRD) and atomic absorption spectrometry (AAS). Over cyclic voltammetry (CV) was used to test its electrochemical activity and to compare the activity of Pd-Ag/C catalyst from different angles. The results showed that the catalyst prepared under the condition of 80 times sodium borohydride had good catalytic performance and good anti poisoning performance.
At the end of this paper, a reasonable suggestion for future research is put forward in connection with the problems in the preparation of catalysts in this paper. The preparation of carbon loaded nanoscale catalysts in this paper has extensive applicability and will have a far-reaching impact on the preparation of other nano catalysts.

【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O643.36;TM911.4

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