【作者】 陈礼敏；

【导师】 包信和；

【作者基本信息】 中国科学院研究生院（大连化学物理研究所） ， 物理化学， 2007， 博士

【摘要】 质子交换膜燃料电池(PEMFC)以纯氢或由甲醇、天然气等碳氢化合物重整得到的氢为燃料,操作温度低(60-80oC)而受到了广泛的关注。但是Pt电极很容易被重整气中微量的CO所毒化,因此低温选择氧化消除富氢中的CO对PEMFC的应用十分重要。本论文重点研究了炭材料担载的Ag、PtAg以及PtFeNi催化剂上CO选择氧化反应的性能,主要研究内容和实验结果包括:(1)系统考察了椰壳基活性炭(AC)载体的孔结构、表面化学性质以及氢气活化对Ag/AC催化剂上反应性能的影响。结果表明高的中孔比表面积有利于提高Ag粒子的分散度,低温达到较高的CO最高转化率;高的微孔比表面积使生成的Ag粒子很大,高温达到较低的CO最高转化率。丰富的表面含氧基团一方面使Ag粒子尺寸呈双峰分布,另一方面又有利于小粒子的生成,催化剂在低温达到较低的CO最高转化率。氢气处理后,AC上可以形成超氧物种;银的存在促进了超氧物种的形成;银存在时超氧物种可以与CO反应,高温活化提高了AC生成超氧物种的能力,从而提高了Ag/AC催化剂的催化性能。(2)研究了碳黑担载的PtAg双金属催化剂的催化性能和结构,并将二者进行关联。结果表明Pt、Ag没有形成明显的合金相,但是二者具有一定的相互作用,从而显示出明显的协同效应。(3)详细的研究了不同炭材料担载的PtFeNi催化剂的催化性能以及Fe和/或Ni对Pt催化剂的促进作用。研究发现含有铁、镍的多壁碳纳米管担载的铂催化剂具有高活性、高选择性、高稳定性并且在室温可以完全消除CO。Fe和/或Ni对Pt催化剂有明显的促进作用;炭材料的电阻率越小则其对应催化剂的催化性能越好。更多还原

【Abstract】 Proton exchange membrane fuel cells (PEMFC), operating at relatively low temperatures (e.g. 60-80oC) with pure hydrogen or reformed gas as fuels, have attracted much attention as a potential power source of electric vehicles. However, the Pt anode catalysts can be seriously poisoned by traces of CO in the reformed gas, which has motivated the search of high efficient catalysts for the CO preferential oxidation in excess H2 at low temperature.The present work was focused on the catalytic properties of carbon materials supported Ag, PtAg, PtFeNi catalysts for CO selective oxidation in H2 feed gas and three parts were included: (1) The effects of textural properties, surface chemistry of activated carbon supports and the roles of hydrogen activation on the activities of Ag/AC catalysts were investigated. The following conclusions can be drawn (a) large amounts of mesopore tend to increase the dispersions of Ag particles, thus, giving higher maximum CO conversion at low temperature; (b) there is maybe negative effect of microporous structure on the dispersions of Ag particles and catalytic performance; (c) rich surface functional groups on one hand make size distribution of Ag particles bimodal, but on the other hand promote the formation of very fine Ag particles, leading to low maximum CO conversion at low temperature; (d) after pretreatment with H2, AC can form superoxide species, O2-; the existence of Ag promotes the formation of superoxide species. With silver, superoxide species can react with CO, the higher pre-treatment temperaturesenhance the formation ability of superoxide species over AC support, leading to better catalytic performance. (2) The catalytic properties and catalyst structure of carbon black supported PtAg bimetal catalysts were investigated. It is found that no obvious PtAg alloy has been observed; however, there maybe exists some interaction between Pt and Ag, leading to evidently synergistic effects for PtAg bimetal catalysts. (3) The Fe and/or Ni promotion and catalytic properties of different carbon materials supported PtFeNi catalysts have been studied in details. It is found that the multiwall carbon nanotubes with Fe and Ni catalyst residues supported Pt catalyst is able to remove all CO at room temperature, with high activity, high selectivity and high stability. The promotion effects of Fe and/or Ni were observed, and the good electron-conductivity of carbon supports played an important role for the good catalytic properties.更多还原