|کد مقاله||کد نشریه||سال انتشار||مقاله انگلیسی||ترجمه فارسی||نسخه تمام متن|
|53352||1419190||2016||5 صفحه PDF||سفارش دهید||دانلود کنید|
• With ambient pressure XPS, the oxidation states of Pt3Ni(1 1 1) surface are measured in in situ.
• Under elevated oxygen pressure, Ni atoms segregate to surface and form surface oxide.
• Pt skin layer is stable under UHV condition.
Utilizing ambient pressure X-ray photoelectron spectroscopy (AP-XPS), the surface segregation and oxidation of Pt3Ni(1 1 1) alloys are investigated as a function of temperature and oxygen pressure. The in situ AP-XPS measurements of oxygen oxidation process show that the Pt “skin” surface is not stable under the exposure of oxygen pressure of 100 mTorr at room temperature. As the temperature and pressure are elevated, the formations of Ni2O3, NiOx, and NiO are observed on surface while Pt atom starts to reduce its adsorbed oxygen, which is a clear sign of surface segregation of Ni to surface. Upon the evacuation of oxygen gas, i.e. ultrahigh vacuum condition, both of NiOx and NiO oxide get reduced and Ni2O3 remains on the surface. The DFT calculation is employed to explain the formation of surface oxides under oxidation condition.
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Journal: Catalysis Today - Volume 260, 1 February 2016, Pages 3–7