【摘要】：燃料電池是一種既有較高能源利用效率又不污染環(huán)境的能源利用方式，在能源短缺、資源爭奪激烈的今天有著巨大的發(fā)展?jié)撃�。然而，陰極緩慢的氧還原反應(yīng)制約了燃料電池大規(guī)模商業(yè)化的發(fā)展進程，尋找高效低耗的氧還原電催化劑成為燃料電池的研究重點。新型負載型合金催化劑的開發(fā)，減小了貴金屬尤其是鉑的擔載量，降低了燃料電池的成本，一定程度上加快了燃料電池的發(fā)展；但由于缺乏對氧還原反應(yīng)機理與動力學(xué)的認識，負載型合金催化劑活化氧還原反應(yīng)的機制尚不清楚，不僅如此，系統(tǒng)研究氧還原的機理與動力學(xué)對氧還原電催化劑的有效設(shè)計也具有重要的指導(dǎo)意義。 本文基于密度泛函理論，系統(tǒng)地研究了含氧石墨烯擔載鉑及鉑合金的負載型合金催化劑催化氧還原反應(yīng)的機理，主要內(nèi)容如下： 在含氧石墨烯中，氧的存在破壞了石墨烯平面的均一性質(zhì)，造成電荷分布不均勻，產(chǎn)生的缺陷位成為金屬負載的活性位點。金屬團簇Pt4，Pt3Ti，Pt3V，Pt3Cr，Pt3Mn，Pt3Fe，Pt3Co和Pt3Ni負載于含氧石墨烯表面后吸附自由態(tài)氧分子，活化后的氧分子以O(shè)-O過渡態(tài)的形式存在于Pt4，Pt3Ti，Pt3Mn，Pt3Fe，Pt3Co和Pt3Ni團簇表面，卻在含氧石墨烯負載的Pt3V和Pt3Cr表面發(fā)生了完全解離，形成了兩個獨立的吸附態(tài)氧原子。過渡金屬原子（Ti，V，Cr，Mn，F(xiàn)e，Co，，Ni）的存在均能有效促進電子向吸附態(tài)氧的轉(zhuǎn)移。 在含氧石墨烯擔載Pt4，Pt3V，Pt3Cr，Pt3Fe，Pt3Co團簇的氧還原反應(yīng)機理研究中，中間體HOO*不能穩(wěn)定存在于催化劑表面，而是會解離成共吸附狀態(tài)的HO*和O*。隨后，在含氧石墨烯擔載的Pt4，Pt3Cr，Pt3Co表面，氧還原過程均能形成共吸附的HO*和共吸附的H2O*與O*，兩種還原路徑都有可能發(fā)生，且以共吸附HO*的還原路徑為熱力學(xué)有利。在含氧石墨烯擔載的Pt3Fe表面，氧還原的過程不僅能形成共吸附的HO*和共吸附的H2O*與O*，且這兩種還原路徑在熱力學(xué)上不分優(yōu)劣，處于競爭關(guān)系。而在含氧石墨烯擔載的Pt3V表面，氧還原的過程不能穩(wěn)定形成共吸附的H2O*與O*，而只能以共吸附的HO*還原路徑為主導(dǎo)。此外，本文的理論研究結(jié)果證實了實驗上觀察到的石墨烯負載Pt3Cr和Pt3Co納米催化劑對活化氧還原反應(yīng)的增強機制。
[Abstract]:Fuel cell is a kind of energy utilization mode which has high energy efficiency and does not pollute the environment. It has great development potential in the shortage of energy and fierce competition for resources. However, the slow oxygen reduction reaction of cathode restricts the development of large-scale commercialization of fuel cell, and the search for high efficiency and low consumption oxygen reduction electrocatalyst has become the research focus of fuel cell. The development of new supported alloy catalysts reduces the loading of precious metals, especially platinum, reduces the cost of fuel cells, and accelerates the development of fuel cells to a certain extent. However, due to the lack of understanding of the mechanism and kinetics of oxygen reduction reaction, the mechanism of oxygen reduction activated by supported alloy catalyst is not clear, not only that, the systematic study of oxygen reduction mechanism and kinetics is also of great significance to the effective design of oxygen reduction electrocatalyst. Based on density functional theory, the mechanism of oxygen reduction catalyzed by platinum supported platinum and platinum alloy catalysts containing oxygen graphene has been systematically studied in this paper. the main contents are as follows: in oxygen graphene, the existence of oxygen destroys the homogeneous property of graphene plane, resulting in uneven charge distribution, and the defect site becomes the active site of metal loading. Metal clusters Pt4,Pt3Ti,Pt3V,Pt3Cr,Pt3Mn,Pt3Fe,Pt3Co and Pt3Ni adsorbed free oxygen molecules on the surface of oxygen-containing graphene. The activated oxygen molecules existed on the surface of Pt4,Pt3Ti,Pt3Mn,Pt3Fe,Pt3Co and Pt3Ni clusters in the form of O 鈮

本文編號：2498248