【作者】 麻博远；

【导师】 雷敏生；

【作者基本信息】 江西师范大学 ， 理论物理， 2003， 硕士

【摘要】 直接甲醇燃料电池（Direct Methanol Fuel Cell，DMFC）是直接使用液体甲醇作燃料，且不需要氢源重整的发电装置。因其燃料来源便利，电池内部结构简单，是一种非常有前途的新型高效化学电源。 本论文的主要研究工作：1．纯Pt催化剂不同晶面的CO“中毒”反应机理研究，并验证从头算法的准确性；2．在此基础上，用从头算法研究Pt-Ru二元合金催化剂CO“中毒”反应的机理。 本文用较小的原子簇模型，模拟Pt（100）和Pt（111）晶面，通过从头算法对CO吸附在Pt（100）和Pt（111）晶面的顶位进行了理论计算。计算结果表明：CO在Pt（100）和Pt（111）晶面顶位吸附的结合能分别为222kJ／mol和175kJ／mol，与近期发表的热力学实验数据吻合得很好。由此我们得到如下结论：1．用小的原子簇模型，结合高精度的理论计算可以对CO吸附在Pt（111）和Pt（100）表面的反应过程进行描述；2．通过计算结果的对比，表明Pt（111）单晶面更不容易发生CO“中毒”，即Pt（111）晶面的催化性能比Pt（100）晶面好。 本文还用原子簇模型近似模拟了CO在Pt-Rt二元合金表面的吸附，计算了它在平衡状态时的结构和振动光谱，发现它们与实验值极其一致。同时我们也发现，在Pt₃Ru₂CO原子簇模型中，Pt-C的键长明显比在Pt_1．4CO原子簇模型中更短，它的结合能为147kJ／mol，也明显低于在Pt_1．4CO原子簇模型中的情况。这说明Pt₃Ru₂原子簇更不容易发生CO“中毒”。通过用射影算子方法，我们对所有原子簇模型中的化学吸附键进行了分析。分析结果显示，虽然σ轨道在成键过程中扮演了主要角色，但是对吸附起决定作用的却是π轨道。几乎在所有原子簇模型中（除了Pt₃Ru₂CO原子簇模型外），CO分子的5σ和2π轨道的布居分布数都近似等于1.5和0.7。 本文的研究为寻找和设计新型直接甲醇燃料电池的催化剂提供了理论参考。更多还原

【Abstract】 Direct methanol fuel cell (DMFC) is an ideal power source due to the high energy density of methanol and convenient fuel management and low system complexity. In the dissertation, carbon monoxide poisoning of the different single-crystal faces of platinum catalysts have been studied. The results provide the precision of Ab initio when it was used to calculate the adsorption of CO on the pure Pt surfaces. Based the precision of Ab initio. carbon monoxide poisoning of the Pt-Ru alloys have been studied.Using the ab initio, we theoretically study the adsorption of CO at the on-top site of the Pt(100) and Pt(111) surfaces in the first part of the dissertation. The binding energies calculated with the Pts cluster models and Pt7 cluster model are 222 kJ/mol and 175 kJ/mol. respectively. These results agree on the recently calorimetric measurements quite well. Our results indicate that Ab initio. which combine small clusters, can be used to simulate the adsorption CO on the pure platinum surface. According to the results, the adsorption CO on Pt(100) surface is more facile.In the second part of the dissertation, we have used the ab initio cluster model approach to study the adsorption of CO on the Pt-Ru alloys surfaces. The calculated equilibrium geometries and vibrational frequencies have been found to be rather in agreement with experimental study. The Pt-C bond length is slightly shorter in the Pt3Ru2CO cluster than in the Pt(1,4)CO cluster, and its adsorption energy is 147 kJ/mol below that for Pt91.4)CO cluster. It accounts that the Pt3Ru2 cluster is not more easily CO "poison". The analysis of the chemisorption bond has been carried out by means of projection operator techniques. These analyses reveal that the bonding interactions are dominated by the π-back-donation although σ-donation plays a significant role. The populations of 5σ and the 2π CO molecular orbitals are about 1.5 and 0.7 electrons expect the Pt3Ru2CO cluster.All these results illustrate the role in which theoretical methods can be used to provide data for combinatorial strategies for discovering and designing new catalysts.更多还原