【摘要】：Pt是一種非常有效的質(zhì)子交換膜燃料電池陰極催化劑,但是其氧還原反應(yīng)速率較慢,這制約了燃料電池的發(fā)展,因此,Pt基二元納米顆粒催化劑已經(jīng)被廣泛研究。為了減少Pt基合金Pt的使用量和增強(qiáng)催化劑的效率和穩(wěn)定性,實(shí)驗(yàn)中研制出了含Pt量少的但具有良好催化活性的納米Pt基合金。另外,附著硼化物的Pt表面也會(huì)起到增強(qiáng)催化劑氧還原反應(yīng)效率。本文利用基于密度泛函理論的第一性原理計(jì)算軟件對(duì)Pt及其合金氧還原反應(yīng)進(jìn)行理論研究。第一,本文研究了PtNi3合金,經(jīng)過電化學(xué)腐蝕,合金表面的Ni流失,剩下的Pt原子重構(gòu)成表面,形成表面富Pt的合金結(jié)構(gòu)。理論研究可以證明這樣的合金結(jié)構(gòu)起到增強(qiáng)氧還原反應(yīng)效率的作用。第二,本文研究了單個(gè)硼原子在Pt(111)面上的穩(wěn)定性,接下來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上存在硼氧化合物時(shí)對(duì)氧原子的吸附過程。另外,在本文中也研究了Pt-BNi膜異質(zhì)結(jié)構(gòu)對(duì)氧還原反應(yīng)催化性能增強(qiáng)的原因。經(jīng)理論研究發(fā)現(xiàn),材料表面的硼原子會(huì)發(fā)生氧化作用,在表面形成BO2或BNiO2團(tuán)簇,然后Pt-BO2結(jié)構(gòu)或Pt-BNiO2結(jié)構(gòu)起到增強(qiáng)氧還原反應(yīng)效率的作用。第三,本文研究了在0.9V的工作電壓下,考慮了溶劑效應(yīng)的影響,以每一反應(yīng)步驟自由能為判據(jù),研究Pt和Pt-BO2表面的氧還原反應(yīng)機(jī)理。經(jīng)理論研究發(fā)現(xiàn),考慮溶劑效應(yīng)時(shí),附著硼化物的Pt表面有增強(qiáng)氧還原反應(yīng)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.
【學(xué)位授予單位】：北京化工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類號(hào)】：O643.36

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