Studies on the Improvement of catalytic performance for direct methanol fuel cell

直接甲醇燃料电池(DMFC)因具有能量转换效率高、污染物排放低、甲醇能量密度高、燃料利用率高等特点而备受关注。但也存在一些问题，制约了直接甲醇燃料电池的应用。这些需要解决的问题包括甲醇活性低和对CO_2的耐受。为了提高甲醇氧化的催化活性，人们对铂合金催化剂进行了大量的研究，以减少催化剂的中毒。本文以聚乙烯吡咯烷酮为稳定剂，采用醇还原法和反相微乳液化学还原法制备了高分散的铂和铂-Ru合金颗粒。用紫外-可见光谱、X-射线衍射、电子显微镜、X-射线光电子能谱、循环伏安法和CO溶出法对催化剂进行了表征。与…相比，前者具有简单性好的优点更多的氯盐直接还原，没有任何改变。在后一种情况下，纳米粒子的平均尺寸约为2-4 nm，分布较窄。此外，它们均匀分散在碳载体上。结果表明，纳米粒子的大小依赖于微乳液中的水量。此外，CO溶出伏安法和CO/H2和甲醇的电化学氧化实验表明，合成的双金属粒子具有较高的比表面积，对CO和甲醇的氧化具有良好的催化活性。铂-Ru-锡催化剂的催化活性明显高于铂-Ru。三元合金催化剂中的锡改性了铂的电子结构，而没有大幅度增加铂-铂键距，这可能通过提高催化剂的抗一氧化碳能力来提高其对甲醇氧化的催化活性。其次，考察了Pt_3Ru_2Fe催化剂的催化活性。提高了催化剂的CO耐受性，使催化剂的甲醇氧化活性提高了2.5倍。较少

Direct methanol fuel cells(DMFC) have been received much attention because of their characteristics such as high energy conversion efficiency, low pollutant emission, high energy density of methanol, and fuel availability. However, there are some problems, inhibiting the application of DMFC. These problems to be solved involve the low activity of methanol and CO_2 tolerance. To enhance the catalytic activity of methanol oxidation, there are intensive researches on Pt alloy catalysts that minimize the catalyst poisoning.In the present work, the highly dispersed Pt and Pt-Ru alloy particles on carbon support were prepared by alcohol-reduction method using polyvinylpyrolidone as a stabilizer, and by chemical reduction method using reverse microemulsion. The prepared catalysts were characterized by UV-visible spectroscopy, x-ray diffraction, electron microscopy, x-ray photoelectron spectroscopy, cyclic voltammetry, and CO striping method. The former method has advantages over simplicity an … More d straight reduction of chloride salt without any modification. In the latter case, the average size of nanoparticle was ca. 2-4 nm with narrow distribution. Moreover, they are homogeneously dispersed on carbon support. It is cleared that the particle size of nanoparticle was dependent on the water volume in microemulsion. In addition, CO stripping voltammetry and the electrochemical oxidations of CO/H_2 and methanol showed that the synthesized bimetallic particles had a high surface area and a good catalytic activity for the oxidations of CO and methanol.The preparation and characterization of Pt_3Ru_2Sn and Pt-Ru-Fe catalysts were investigated. The catalytic activity of Pt-Ru-Sn catalyst was significantly higher than that of Pt-Ru. Sn in ternary alloy catalyst modified the Pt electric structure without the large increase of Pt-Pt bond distance, which may enhance the catalytic activity for methanol oxidation by improving CO tolerance. Next, the catalytic activity of Pt_3Ru_2Fe catalyst was studied. The activity of methanol oxidation of Pt_3Ru_2Fe catalyst was 2.5 times higher than that of Pt-Ru catalyst by the enhanced CO tolerance. Less