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عنوان فارسی مقاله:
مطالعه جذب اشعه X از نانوذرات پالادیم و مس سریا پشتیبانی شده برای تغییرات بخار آب اکسیژن افزایش یافته
عنوان انگلیسی مقاله:
In-situ X-ray absorption study of ceria-supported Pd-Cu nanoparticles for oxygen-enhanced water gas shift
سال انتشار : 2016
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مقدمه انگلیسی مقاله:
1. Introduction
Water gas shift (WGS) is one of the key steps in fuel processing for H2 production for low-temperature fuel cell applications [1,2]. Cu-based catalysts have traditionally been employed for this reaction [3]. In the case of a Cu-Zn-Al oxide catalyst, a linear relationship was obtained between copper surface area and activity, but the linearity is not valid when the preparation method differs, meaning that the WGS is structure-sensitive [4]. Zinc and aluminum oxides are used as the support of catalyst where zinc addition increases the specific rate (activity per Cu surface area) through decrease of heat of CO adsorption [5] and increases dispersion of Cu while aluminum addition only disperses the Cu phase [6]. Although numerous efforts have been made for increasing activity and stability, the Cu-based catalysts have drawbacks of easy sintering and pyrophoricity [1]. CeO2-supported Cu catalyst is one of the non-pyrophoric alternatives. While the surface of Cu/Al2O3 is saturated with a copper surface phase, fine CuO crystallites are formed on Cu/CeO2/Al2O3catalyst due to an interaction between the CeO2 and copper phase [7]. Thus, the reaction pathway should be different. Copper is immiscible to CeO2 lattice and enrichment of copper on the surface was identified by XPS [8]. Proposed active sites includes Cu1+ species that originates from interaction of copper clusters with oxygen species on ceria surface [9], and an isolated copper oxo species formed on CeO2-containig supports [10]. In the effort to improve WGS activity at low temperature, our group has developed a method called oxygen-enhanced water gas shift (OWGS) in which a small amount of oxygen is added to a WGS feed [11]. Since catalyst should stand the oxidative condition, a new formulation, CeO2-supported Pd-Cu and Pt-Cu catalysts, were developed. We have found that with these catalysts CO shift is significantly promoted by O2 addition to the feed without deactivation [12]. Through kinetic analysis, we found that CO order is low on monometallic noble metal (Pd or Pt) due to high CO coverage on the active surface while CO order is high on Cu and it is moderate on Pd-Cu and Pt-Cu bimetallics. H2O order showed an opposite trend to the CO order, which suggested that the reaction proceeds through the association of chemisorbed reactants [13]. By adding oxygen into the feed, only the CO order increased, which suggested that oxygen removes the chemisorbed CO to free up the sites for H2O chemisorption and to balance these surface reactants. The oxygen addition did not promote CO shift on Al2O3-supported catalyst and low-surface-area CeO2-supported catalyst (<2 m2/g)while over 90 m2/g of surface area the turnover rate leveled off for CeO2-supported catalysts [14]. However, the structural variation of Pd-Cu on different supports and its impacts on catalytic performance were not yet clear. In the present study, X-ray absorption fine structure of Pd-Cu bimetallic catalysts was investigated to find the factor to controlthe catalytic activity.We have also investigated the Pd-Cu structure in an in-situ CO shift atmosphere.
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کلمات کلیدی:
Using in situ environmental transmission microscopy and operando X ... onlinelibrary.wiley.com › ... › European Microscopy Congress 2016: Proceedings by AM Gänzler - Related articles Dec 20, 2016 - ... operando X-ray absorption spectroscopy to investigate ceria based ... In the present study, ceria supported catalysts were investigated for ... In-situ X-ray Spectroscopy publications | Paul Scherrer Institut (PSI) https://www.psi.ch/group-superxas/publications Publications of the In-situ X-ray Spectroscopy group .... DOI: 10.1039/c4cp03226h; Catalytically Active and Spectator Ce3+ in Ceria-Supported Metal Catalysts .... to extended x-ray-absorption fine structure in a new cell to study solid catalysts ... In Situ Characterization of Highly Dispersed, Ceria-Supported Fe Sites ... pubs.acs.org/doi/abs/10.1021/jp5126975 by CA Roberts - 2015 - Cited by 8 - Related articles Jan 29, 2015 - In situ X-ray absorption spectroscopy with simultaneous gas-phase monitoring ... Monolayer Detection of Supported Fe and Co Oxides on Ceria To ... DFT+U Study of the Adsorption and Oxidation of an Iron Oxide Cluster on ... In-situ extended X-ray absorption fine structure study of electrostriction ... scitation.aip.org/content/aip/journal/apl/106/4/10.1063/1.4906857 by R Korobko - 2015 - Cited by 12 - Related articles Accepted: January 2015 .... Gd-doped ceria is one of the most extensively studied oxygen ion conductors.8. ... As we show below using in situ differential X-ray absorption spectroscopy (differential XAS), the structural changes associated with ... Operando Research in Heterogeneous Catalysis https://books.google.com/books?isbn=3319444395 Joost Frenken, Irene Groot - 2016 - Science ... in heterogeneous catalysts probed by in situ X-ray absorption techniques. ... et al., XAFS spectroscopy; fundamental principles and data analysis. ... R. Kopelent et al., Catalytically active and spectator Ce3+ in ceria-supported metal catalysts. X-ray absorption study of ceria nanorods promoting ... - RSC Publishing pubs.rsc.org/en/content/articlehtml/2016/CC/C5CC10643E by TS Wu - 2016 - Cited by 4 - Related articles Mar 7, 2016 - Received 30th December 2015 , Accepted 3rd March 2016 ... A quasi in situ X-ray absorption study demonstrated that the disproportionation of ...
