發(fā)布時間：2018-05-15 01:40

  本文選題：直接甲醇燃料電池 + 陽極催化劑��； 參考：《太原理工大學》2015年碩士論文

【摘要】：隨著人類社會的進步，人們對能源和環(huán)境問題有了更深入的認識，環(huán)保新能源已成為世界各國能源發(fā)展戰(zhàn)略的核心。直接甲醇燃料電池（DMFC）因具有高效、低污染、燃料易獲取儲存和運輸等優(yōu)勢而成為開發(fā)與研究的熱點，可廣泛應用于汽車、飛機、航天、航海等領域。但在燃料電池的實際應用中電池成本過高，能量轉化效率偏低等問題一直困擾著燃料電池的商業(yè)化運用。其根本原因則在于現有條件下電催化劑價格昂貴且效率不高，因此研制廉價高效催化劑具有重要意義。本論文采用鈀、銀等金屬鹽作為前驅化合物，通過PVP保護的方法將相應金屬負載于Vulcan XC-72活性碳表面，制備負載型的納米催化劑以達到提高金屬的反應接觸面積從而提高單位質量金屬的利用效率并降低成本。 首先，采用以XC-72活性炭為載體,用堿（NaOH、氨水）調節(jié)溶液的酸堿性，用NaBH4作還原劑制備Pd/C催化劑，篩選制作催化劑的最佳配方。通過透射電鏡（TEM）,X-射線衍射（XRD）及原子吸收光譜法（AAS），對催化劑的結構、形貌及金屬的實際負載量進行表征，并通過循環(huán)伏安法（CV）測試其電化學活性，從不同角度分析比較Pd/C催化劑的活性。結果顯示，堿的添加對提高了鈀的負載量，而弱堿氨水的效果要優(yōu)于強堿氫氧化鈉；而在相同體系下，3ml氨水為最佳使用量。測試結果還顯示，氨水的添加不但提高了金屬鈀的負載量，還改善了金屬鈀納米顆粒的分散程度及其粒徑，其中以3ml氨水條件下的催化劑金屬顆粒最小，分散程度最均勻。在添加3ml氨水的條件下，發(fā)現不同的還原劑添加量也會影響到鈀的粒徑及分散程度。實驗表明，在其他條件相同的情況下，投加160倍硼氫化鈉所制備的催化劑顯示了最好的性能。最后得出，在該實驗條件下的催化劑的最佳配方為，在反應溶液為200ml的條件下，，加入PVP1,252g，PdCl20.02g，160倍硼氫化鈉，3ml1mol/L氨水。 此外，本論文還研究了炭載銀催化劑的制備及其電催化活性。由于銀在元素周期表中與鈀同周期并在相鄰主族，故與鈀具有相似性。更為重要的是銀與鈀相比具有極大的價格優(yōu)勢，因此對于Ag作為陽極催化性能的研究是非常有必要的。本研究分別采用加40倍、80倍、160倍硼氫化鈉制備Ag/C催化劑，通過透射電鏡（TEM）,X-射線衍射（XRD）及原子吸收光譜法（AAS），對催化劑的結構、形貌及金屬的實際負載量進行表征，并通過循環(huán)伏安法（CV）測試其電化學活性，從不同角度分析比較Ag/C催化劑的活性。研究結果表明，隨著加入還原劑量的增加。催化活性逐漸升高。研究還發(fā)現，加入不同量的還原劑并未影響催化劑的負載量，而影響到了金屬顆粒的大小和分散性。結果表明在160倍硼氫化鈉條件下制備的Ag/C催化劑中銀納米粒子粒徑均勻，分散性較好，電化學性最高。但是，相比單金屬鈀納米催化劑，銀的粒徑較大導致其催化活性不如Pd/C催化劑。 關于Pd/C和Ag/C催化劑的研究中發(fā)現，Pd與Ag的催化特征各有千秋。若綜合兩者優(yōu)勢，有可能會獲得更為理想的催化劑。為此本論文在此前的研究基礎上以Vulcan XC-72為載體通過溶膠法制備了炭載Pd-Ag雙金屬納米催化劑。加入NaOH調節(jié)溶液的酸堿性，并通過改變硼氫化鈉的添加量控制晶體生長。本研究分別在40倍、80倍、160倍硼氫化鈉條件下制備Pd-Ag/C催化劑樣品，通過透射電鏡（TEM）,X-射線衍射（XRD）及原子吸收光譜法（AAS），對催化劑的結構、形貌及金屬的實際負載量進行表征，并通過循環(huán)伏安法（CV）測試其電化學活性，從不同角度分析比較Pd-Ag/C催化劑的活性。研究結果顯示，在80倍硼氫化鈉的條件下制備的催化劑不但具有良好的催化性能，且抗中毒性能良好。 文末結合本論文中制備催化劑所存在的問題，對未來的研究工作提出了合理的建議。本論文述及的制備炭載型納米催化劑的方法具有廣泛的適用性，將對其它的納米催化劑制備產生深遠的影響。
[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.

【學位授予單位】：太原理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：O643.36;TM911.4

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