化学学报 ›› 2017, Vol. 75 ›› Issue (2): 189-192.DOI: 10.6023/A16080451 上一篇    下一篇

所属专题: 先进电池材料

研究通讯

锗纳米管催化的氧还原反应:催化性能和机理研究

陈鑫a,b, 鄢慧君a, 夏定国a   

  1. a 北京大学工学院 先进电池材料理论与技术北京市重点实验室 北京 100871;
    b 西南石油大学化学化工学院 新能源材料与技术研究中心 成都 610500
  • 收稿日期:2016-08-29 修回日期:2016-10-09 出版日期:2017-02-15 发布日期:2016-10-10
  • 通讯作者: 夏定国,E-mail:dgxia@pku.edu.cn;Tel.:010-62767962;Fax:010-62767962 E-mail:dgxia@pku.edu.cn
  • 基金资助:

    项目受国家自然科学基金(Nos.51602270,51671004)资助.

Germanium Nanotube as the Catalyst for Oxygen Reduction Reaction: Performance and Mechanism

Chen Xina,b, Yan Huijuna, Xia Dingguoa   

  1. a Beijing Key Laboratory for Theory and Technology of Advanced Battery Materials, College of Engineering, Peking University, Beijing 100871;
    b The Center of New Energy Materials and Technology, College of Chemistry and Chemical Engineering, Southwest Petroleum University, Chengdu 610500
  • Received:2016-08-29 Revised:2016-10-09 Online:2017-02-15 Published:2016-10-10
  • Contact: 10.6023/A16080451 E-mail:dgxia@pku.edu.cn
  • Supported by:

    Project supported by the National Natural Science Foundation of China (Nos. 51602270, 51671004).

应用密度泛函理论,在DZP基组水平上研究了(5,5)型锗纳米管催化的氧还原反应(ORR)的性能以及可能的催化机理.计算结果表明,ORR在锗纳米管上可能经历O2解离、OOH解离、H2O2解离三种可能机理.无论是对哪种机理,整个ORR均遵循四电子反应路径.评估ORR性能的重要中间产物O和OH的吸附能分别为-4.33 eV和-2.21 eV,这与它们在贵金属铂(Pt)上的吸附能非常接近.此外,在GeNT上,整个ORR过程中最后一步生成的H2O分子的吸附能仅仅为-0.05 eV,比O2分子的吸附能弱得多,意味着整个ORR催化循环在GeNT上可以顺利更替.因此,联合ORR的反应能量数据和中间产物的吸附数据,可以认为(5,5)型锗纳米管具有类Pt的催化性能.溶剂效应计算结果表明,一些反应中间产物的吸附结构,如O中间体会在很大程度上受到溶剂效应的影响.对所研究的锗纳米管来说,溶剂效应可以促进其催化的ORR进程.

关键词: 锗纳米管, 氧还原反应, 溶剂效应, 密度泛函理论

One of the major technical barriers to the commercialization of proton exchange membrane fuel cells is the high cost of Pt-based oxygen reduction reaction (ORR) electrocatalysts. In this paper, the ORR catalytic performance and the possible mechanism on (5,5) germanium nanotube (GeNT) were studied by density functional theory methods using DZP basis set. The results indicate that the ORR on the GeNT may undergo three mechanisms including O2 dissociation, OOH dissociation and H2O2 dissociation. For any of the above mechanism, the whole process could easily take place on the GeNT with a complete 4e- ORR pathway. The adsorption properties of the ORR intermediates, especially for O and OH, are also very important for evaluating the catalytic performance. The calculated adsorption energies of the above species are -4.33 and -2.21 eV respectively, much close to those on the Pt. Furthermore, the adsorption energy of H2O on the GeNT is only -0.05 eV, much weaker than the O2 binding, indicating the catalytic cycle of ORR could repeat most easily on the GeNT. Therefore, both the reaction energies of the ORR steps and the adsorption energies of ORR intermediates show that the current GeNT model has the catalytic performance similar to that of precious Pt catalyst. Furthermore, the solvent effect was also studied by using three-water-molecule clusters as the real solvent. The obtained results indicate that the solvent effect could affect the geometrical structure of some adsorbed ORR intermediates, such as atomic O. This would lead to the decrease of the heat loss during the O2 dissociation mechanism. The decreased heat loss would accelerate the following electron transfer steps, due to the fact that an effective electrocatalyst must make the energy loss as small as possible for non-electron-transfer step, in which case the cathode electrocatalyst would deliver all the Gibbs energy of the ORR as electrical work. With solvation, the heat loss is slightly increased from *O2 to *OOH, and decreased from *OOH to *OH in the H2O2 dissociation mechanism, which are also more favorable for ORR.

Key words: germanium nanotube, oxygen reduction reaction, solvent effect, density functional theory (DFT)