Fe-N-C氧还原催化剂的第一性原理研究

FIRST-PRINCIPLES STUDY OF FE-N-C OXYGEN REDUCTION CATALYST

陈昭杨

11849414

硕士

物理学

黄丽

2020-05-29

2020-07-07

哈尔滨工业大学

深圳

化石燃料的巨大消耗导致了一系列环境污染和气候变化等问题，因而可持续清洁能源的合理利用就变得尤为重要。质子交换膜燃料电池具有运行安静、启动快速，能量转换效率高和无污染物排放等优点，它被认为是一种极具潜力的固定、便携式和车载应用的清洁电源。然而，由于其阴极催化剂存在成本高昂和催化活性不足等问题，使得燃料电池的商业化进程受到了阻碍。因此，开发出催化活性高以及成本低廉的新型催化剂变得尤为重要。Fe-N-C氧还原催化剂因其来源丰富、成本低廉以及较高的活性而被普遍认为是铂基贵金属最有潜力的替代品之一。本文通过密度泛函理论的第一性原理计算方法，研究了有少量Fe3C/Fe修饰的FeN4以及两种Fe-N-C/MXene催化剂的氧还原电催化活性。本论文的主要内容和结果可分为如下几个部分：第一部分是以FeN4和有少量Fe3C/Fe修饰的FeN4为模型研究了它们的氧还原反应催化机理。利用第一性原理计算得到了其氧还原反应中氧气的吸附特性，并通过Bader电荷分析了原子的得失电子情况，发现有Fe3C/Fe团簇修饰的FeN4催化剂，其吸附的氧原子周围会积累更多的额外电荷，从而产生相对较大的吸附能并促进氧还原反应的活性。除此之外，还计算了催化剂对氧还原反应中间体的吉布斯自由能，从而得到氧还原反应路径。研究表明催化剂的活性控制步骤发生在OH的脱附反应上，并且计算得到的过电势也表明Fe3C/Fe的修饰的确能改善FeN4的催化活性，即Fe3C/Fe与FeN4间具有协同效应。第二部分是以Fe-N-C/Mo2C和Fe-N-C/V2C为模型研究了其氧还原反应的催化活性。利用第一性原理计算得到催化剂对含氧中间体的吉布斯自由能，由此得到氧还原反应路径。研究表明，催化剂的活性控制步骤发生在OH的脱附反应上，并且催化剂的氧还原活性顺序为：G-Mo2C-hollow > G-Mo2C-top > G-V2C-hollow≈G-V2C-top。除此以外，通过对催化剂d能带中心的分析，发现d能带中心数值越正，含氧中间体OH的脱附越困难，催化剂的催化效果越差。

The huge consumption of fossil fuels has caused a series of problems such as environmental pollution and climate change, so the rational use of sustainable clean energy has become particularly important. The proton exchange membrane fuel cell has the advantages of quiet operation, fast startup, high energy conversion efficiency and no pollutant emissions. It is considered to be a clean power source with great potential for fixed, portable and vehicle applications. However, due to the high cost and insufficient catalytic activity of its cathode catalyst, the commercialization of fuel cells has been hindered. Therefore, it has become particularly important to develop new catalysts with high catalytic activity and low cost. Fe-N-C oxygen reduction catalyst is generally considered to be one of the most potential substitutes for platinum-based precious metals because of its rich source, low cost and high activity. In this thesis, the oxygen reduction electrocatalytic activity of FeN4 modified with a small amount of Fe3C / Fe and two Fe-N-C / MXene catalysts was studied by density functional theory. The main content and results of this paper can be divided into the following parts: In the first part, FeN4 and FeN4 modified with a small amount of Fe3C / Fe were used as models to study their catalytic mechanism of oxygen reduction. Using the first-principles calculation, the oxygen adsorption characteristics of the oxygen reduction reaction were calculated, and the electron gain and loss of the atoms were analyzed by Bader charge. It was found that the FeN4 catalyst modified by Fe3C / Fe clusters will accumulate more extra charge around the adsorbed oxygen atoms, which produces a relatively large adsorption energy and promotes the activity of the oxygen reduction reaction. In addition, the Gibbs free energy of the catalyst for the oxygen reduction reaction intermediate is also calculated, thereby obtaining the oxygen reduction reaction path. Studies have shown that the activity control step of the catalyst occurs on the desorption reaction of OH, and the calculated overpotential also indicates that the modification of Fe3C / Fe can indeed improve the catalytic activity of FeN4, that is, Fe3C / Fe and FeN4 have a synergistic effect. The second part studied the catalytic activity of the oxygen reduction reaction with Fe-N-C / Mo2C and Fe-N-C / V2C as models. Using the first-principles calculation, the Gibbs free energy of the catalyst to the oxygen-containing intermediate is obtained, thereby obtaining the oxygen reduction reaction path. Studies have shown that the activity control step of the catalyst occurs on the desorption reaction of OH, and the order of the oxygen reduction activity of the catalyst is: G-Mo2C-hollow> G-Mo2C-top> G-V2C-hollow≈G-V2C-top. In addition, through the analysis of the d band center of the catalyst, it is found that the more positive the d band center value, the more difficult the desorption of the oxygen-containing intermediate OH, and the worse the catalytic effect of the catalyst.

质子交换膜燃料电池 Fe-N-C 氧还原反应 第一性原理 d能带中心

proton exchange membrane fuel cell Fe-N-C oxygen reduction reaction first-principles d band center

中文

联合培养

南方科技大学

陈昭杨. Fe-N-C氧还原催化剂的第一性原理研究[D]. 深圳. 哈尔滨工业大学,2020.