کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
10243698 | 47156 | 2005 | 10 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Bistability and oscillations in CO oxidation studied with scanning tunnelling microscopy inside a reactor
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کلمات کلیدی
Oxidation - اکسیداسیونSolid–gas interfaces - رابط های جامد گازSingle crystal surfaces - سطوح کریستال تکCatalysis - فروکافت یا کاتالیزModels of surface chemical reactions - مدل های واکنش های شیمیایی سطحcarbon monoxide - منوکسیدکربنScanning tunnelling microscopy - میکروسکوپ تونلی اسکن کردنPalladium - پالادیوم یا پالادیمPlatinum - پلاتین
موضوعات مرتبط
مهندسی و علوم پایه
مهندسی شیمی
کاتالیزور
پیش نمایش صفحه اول مقاله
![عکس صفحه اول مقاله: Bistability and oscillations in CO oxidation studied with scanning tunnelling microscopy inside a reactor Bistability and oscillations in CO oxidation studied with scanning tunnelling microscopy inside a reactor](/preview/png/10243698.png)
چکیده انگلیسی
This article focuses on the microscopic origin of oscillations in the rate of CO oxidation at atmospheric pressures on Pt group metals. We start by briefly reviewing several existing models for oscillatory CO oxidation on such surfaces at pressures ranging from ultrahigh vacuum to several bar. We describe our observations for this reaction on Pt(1Â 1Â 0) and Pd(1Â 0Â 0) at atmospheric pressures, obtained with a scanning tunnelling microscope inside a microflow reactor. The combination of STM movies and the simultaneously determined partial pressures and reaction rate reveals that by switching between a CO-rich flow and an O2-rich flow, and vice versa, we can reversibly oxidize and reduce the Pt and Pd surfaces. We find that on both surfaces the formation of the oxide, seen in the STM images, is accompanied by a stepwise increase in the reaction rate and a change in the reaction mechanism. The switching between the reduced metal and the surface oxide exhibits significant hysteresis as a function of CO pressure and for both Pt and Pd there exists a CO pressure window in which both the metal and the oxide state are stable. This bistabililty leads to spontaneous reaction oscillations on Pd(1Â 0Â 0). Under our atmospheric conditions these oscillations are not due to the 'familiar' bistability in Langmuir-Hinshelwood kinetics, in contrast with common 'wisdom'. Instead, the high-pressure reaction oscillations reflect the periodic switching between the low-reactivity metallic surface and the high-reactivity oxide surface. Our results show further that effects that are held responsible for low-pressure reaction oscillations are not relevant at atmospheric pressure.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Catalysis Today - Volume 105, Issue 2, 30 July 2005, Pages 234-243
Journal: Catalysis Today - Volume 105, Issue 2, 30 July 2005, Pages 234-243
نویسندگان
B.L.M. Hendriksen, S.C. Bobaru, J.W.M. Frenken,