دانلود رایگان مقاله مطالعه جذب اشعه X از نانوذرات پالادیم و مس سریا پشتیبانی شده

عنوان فارسی
مطالعه جذب اشعه X از نانوذرات پالادیم و مس سریا پشتیبانی شده برای تغییرات بخار آب اکسیژن افزایش یافته
عنوان انگلیسی
In-situ X-ray absorption study of ceria-supported Pd-Cu nanoparticles for oxygen-enhanced water gas shift
صفحات مقاله فارسی
0
صفحات مقاله انگلیسی
7
سال انتشار
2016
نشریه
الزویر - Elsevier
فرمت مقاله انگلیسی
PDF
کد محصول
E2107
رشته های مرتبط با این مقاله
شیمی
گرایش های مرتبط با این مقاله
شیمی کاتالیست، شیمی تجزیه
مجله
کاتالیز های کاربردی A: عمومی - Applied Catalysis A: General
دانشگاه
موسسه انرژی EMS، بخش انرژی و مهندسی معدنی، دانشگاه ایالتی پنسیلوانیا
کلمات کلیدی
تمدید جذب اشعه ایکس ساختار ریز، CeO2-پشتیبانی از Pd-مس، کاتالیزور دو فلزی، آلیاژ PD-مس، تغییرات بخار آب، اکسیژن افزایش یافته است (WGS)
چکیده

ABSTRACT


 The detailed structures of bimetallic Pd-Cu on various CeO2 and Al2O3 supports were investigated by X-ray absorption technique in-situ in hydrogen and WGS conditions. No indication of the neighboring Pd atoms in both Pd-K edge and Cu-K edge EXAFS fittings showed that Pd is highly dispersed in the lattice of metallic Cu. The Cu-Cu bond distance was markedly shortened by alloying with Pd and correlated to decrease of coordination number, which reflects particle size. A higher coordination number for Pd-Cu than that for Cu-Cu on Al2O3 support suggested that Pd is in the interior of the nanoparticles on Al2O3 while these coordination numbers were close on CeO2 support indicating a uniform distribution of Pd and Cu atoms. The CO shift activity was not simply correlated to the Cu-Cu bond distance or particle size, but the high activity of Pd-Cu/CeO2 was attributed to surface Pd interacting with Cu on CeO2 surface.

نتیجه گیری

4. Conclusions


Using the X-ray absorption technique, the local structures of Pd and Cu in Pd-Cu catalysts were investigated in comparison with monometallic catalysts. From Cu K-edge spectra, only Cu neighbors were recognized and Pd neighbor was invisible. The particle size estimated from the Cu-Cu coordination number was much smaller for Pd-Cu system than monometallic Cu. The Cu-Cu bond distance in the Pd-Cu system was much shorter than that of monometallic Cu, which was correlated to the small particle size. The Pd K-edge XANES looks like an alloy, but in the EXAFS spectra, only Cu neighbors were identified. Thus, Pd is atomically dispersed in the Cu lattice. The Fourier transform of Pd K-edge spectra showed that Pd is geometrically identicalto Cu, i.e.the Pd-Cu bond distance is much shorter than that of monometallic Pd (2.75Å) and is close to Cu-Cu bond distance of monometallic Cu (2.55Å). Although such structural feature (small particle size and lattice shrinkage) of Pd-Cu is not a sole factor for the enhanced CO shift activity, the interactions among these two metal components and CeO2 support were suggested to control the CO shift activity.


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