铂及其合金氧还原反应第一性原理理论研究

发布时间：2018-08-18 12:37

【摘要】：Pt是一种非常有效的质子交换膜燃料电池阴极催化剂,但是其氧还原反应速率较慢,这制约了燃料电池的发展,因此,Pt基二元纳米颗粒催化剂已经被广泛研究。为了减少Pt基合金Pt的使用量和增强催化剂的效率和稳定性,实验中研制出了含Pt量少的但具有良好催化活性的纳米Pt基合金。另外,附着硼化物的Pt表面也会起到增强催化剂氧还原反应效率。本文利用基于密度泛函理论的第一性原理计算软件对Pt及其合金氧还原反应进行理论研究。第一,本文研究了PtNi3合金,经过电化学腐蚀,合金表面的Ni流失,剩下的Pt原子重构成表面,形成表面富Pt的合金结构。理论研究可以证明这样的合金结构起到增强氧还原反应效率的作用。第二,本文研究了单个硼原子在Pt(111)面上的稳定性,接下来探究了硼原子和氧原子的相互作用及硼氧化物的形成方式,最后,探究了Pt上存在硼氧化合物时对氧原子的吸附过程。另外,在本文中也研究了Pt-BNi膜异质结构对氧还原反应催化性能增强的原因。经理论研究发现,材料表面的硼原子会发生氧化作用,在表面形成BO2或BNiO2团簇,然后Pt-BO2结构或Pt-BNiO2结构起到增强氧还原反应效率的作用。第三,本文研究了在0.9V的工作电压下,考虑了溶剂效应的影响,以每一反应步骤自由能为判据,研究Pt和Pt-BO2表面的氧还原反应机理。经理论研究发现,考虑溶剂效应时,附着硼化物的Pt表面有增强氧还原反应催化效率的作用。
[Abstract]:Pt is a very effective cathode catalyst for proton exchange membrane fuel cells, but its oxygen reduction rate is slow, which restricts the development of fuel cells. In order to reduce the use of Pt and enhance the efficiency and stability of the catalyst, nanocrystalline Pt-base alloys with low Pt content and good catalytic activity were prepared. In addition, the Pt surface with boride can enhance the efficiency of oxygen reduction reaction. In this paper, the oxygen reduction reaction of Pt and its alloys has been studied theoretically by using the first-principle calculation software based on density functional theory (DFT). Firstly, the PtNi3 alloy is studied. After electrochemical corrosion, Ni is lost on the surface of the alloy, and the remaining Pt atoms form the surface of the alloy, forming the structure of the Pt-rich alloy on the surface. Theoretical study shows that this alloy structure can enhance the efficiency of oxygen reduction reaction. Secondly, the stability of single boron atom on Pt (111) surface is studied. The interaction between boron atom and oxygen atom and the formation of boron oxide are studied. Finally, the adsorption process of oxygen atom on Pt with boron oxide is investigated. In addition, the reasons for the enhancement of catalytic performance of Pt-BNi heterostructure for oxygen reduction have also been studied in this paper. It is found that boron atoms on the surface of the material will be oxidized, forming BO2 or BNiO2 clusters on the surface, and then the Pt-BO2 or Pt-BNiO2 structure can enhance the efficiency of oxygen reduction reaction. Thirdly, under the operating voltage of 0.9V, the effect of solvent effect is considered, and the mechanism of oxygen reduction on Pt and Pt-BO2 surface is studied based on the free energy of each reaction step. It is found that the surface of Pt with boride adhesion can enhance the catalytic efficiency of oxygen reduction reaction when the solvent effect is taken into account.
【学位授予单位】：北京化工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O643.36

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