本文研究二元及三元白金合金觸媒 (添加Fe、Co、Ni、Cu) 應用於質子交換膜燃料電池之陰極觸媒。觸媒的微結構、晶體結構與電子結構特性分別以TEM、XRD與XPS分析鑑定。TEM影像顯示奈米金屬顆粒均勻地分佈在碳載體XC-72表面上，但不同合金成份的觸媒顆粒大小有些許的差異。由XRD繞射圖譜可以看出二元或三元合金的結晶結構都與純白金同樣屬於fcc結構，並且白金合金的晶格常數皆比純白金小。其中，晶格常數PtCu < PtNi < PtCo < PtFe，因此Cu為本研究中最有利於“幾何結構因素”之合金元素。大部分之合金在XPS能譜圖中，Pt-4f電子束縛能會往高能位移，其表示5d軌域空位有增加的情形。其中，化學位移PtFe > PtCo > PtNi > PtCu，因此Fe為最有利於“電子結構因素”之合金元素。 由循環伏安法可以量測觸媒之比活性、重量活性與電化學活性面積。然而，觸媒活性受到觸媒顆粒大小影響，因此在比較活性時需特別注意觸媒之顆粒尺寸。本研究發現比活性在Pt-Pt原子間距等於2.71 – 2.72 Å有最大值，而電子結構因素之影響在本研究中並不明顯。 Pt-based binary and ternary alloy catalysts (alloying with Fe, Co, Ni and Cu) as cathode materials for PEMFC were investigated. The morphology, crystal structure and electronic structure were analyzed by TEM, XRD, and XPS. TEM images show the metal particles are dispersed on the XC-72 uniformly, but the particle size of various catalysts with different compositions are slightly different. All prepared alloy catalysts exhibit fcc structure and have smaller lattice constants than pure Pt. The order of lattice constants for binary alloy catalysts is PtCu < PtNi < PtCo < PtFe. This result conforms to the atomic radii of these transition metals. Therefore, Cu owns the greatest “geometric factor”. In XPS spectra, positive chemical shifts of Pt-4f are observed for most of the alloy catalysts studied, indicating that the 5d vacancy of Pt is increased by alloying. The amount of positive chemical shift for binary alloy catalysts is in the order of PtFe > PtCo > PtNi > PtCu. It shows Fe exhibits the greatest “electronic factor”. The specific activity, mass activity and electrochemical surface area are obtained from CV analysis. Because the activity depends on the particle size, the comparison between the catalysts must be done very carefully. We observe that the maximum specific activity occur for the catalyst with a Pt-Pt neighbor distance of 2.71 – 2.72 Å. The influence of electronic property to the activity in our study is not obvious. We conclude that the effect of geometric property is more important than electronic property.
