Ceria-based catalytic materials are known for their crystal-face-dependent catalytic properties.To obtain a molecular-level understanding of their surface chemistry,controlled synthesis of ceria with well-defined surf...Ceria-based catalytic materials are known for their crystal-face-dependent catalytic properties.To obtain a molecular-level understanding of their surface chemistry,controlled synthesis of ceria with well-defined surface structures is required.We have thus studied the growth of CeOx nanostructures(NSs)and thin films on Pt(111).The strong metal-oxide interaction has often been invoked to explain catalytic processes over the Pt/CeOx catalysts.However,the Pt-CeOx interaction has not been understood at the atomic level.We show here that the interfacial interaction between Pt and ceria could indeed affect the surface structures of ceria,which could subsequently determine their catalytic chemistry.While ceria on Pt(111)typically exposes the CeO2(111)surface,we found that the structures of ceria layers with a thickness of three layers or less are highly dynamic and dependent on the annealing temperatures,owing to the electronic interaction between Pt and CeOx.A two-step kinetically limited growth procedure was used to prepare the ceria film that fully covers the Pt(111)substrate.For a ceria film of^3–4 monolayer(ML)thickness on Pt(111),annealing in ultrahigh vacuum(UHV)at 1000 K results in a surface of CeO2(100),stabilized by a c-Ce2O3(100)buffer layer.Further oxidation at 900 K transforms the surface of the CeO2(100)thin film into a hexagonal CeO2(111)surface.展开更多
To investigate the effects of chlorine on the Au/ceria catalysts,the adsorption of gold or chlorine and their coadsorpiton on the stoichiometric and partially reduced CeO2（111） surfaces are studied from the first pr...To investigate the effects of chlorine on the Au/ceria catalysts,the adsorption of gold or chlorine and their coadsorpiton on the stoichiometric and partially reduced CeO2（111） surfaces are studied from the first principles.It is found that the adsorption of Au is significantly enhanced by the chlorine preadsorption on the stoichiometric CeO2（111） surface;while on the partially reduced CeO2（111） surface,the preadsorbed chlorine inhabits the oxygen vacancy（which is the preferred adsorption site for gold）,leading to a CeOCl phase and the dramatical weakening of the Au adsorption.Therefore,chlorine on the CeO2（111） surface can affect the Au adsorption thus the activity of the Au/CeO2 catalyst.展开更多
Density functional theory calculations were carried out to investigate the influence of doping transition metal(TM) ions into the ceria surface on the activation of surface lattice oxygen atoms. For this purpose, the ...Density functional theory calculations were carried out to investigate the influence of doping transition metal(TM) ions into the ceria surface on the activation of surface lattice oxygen atoms. For this purpose, the structure and stability of the most stable(111) surface termination of CeO2 modified by TM ions was determined. Except for Zr and Pt dopants that preserve octahedral oxygen coordination, the TM dopants prefer a square-planar coordination when substituting the surface Ce ions. The surface construction from octahedral to square-planar is facile for all TM dopants, except for Pt(1.14 e V) and Zr(square-planar coordination unstable). Typically, the ionic radius of tetravalent TM cations is much smaller than that of Ce4+, resulting a significant tensile-strained lattice and explaining the lowered oxygen vacancy formation energy. Except for Zr, the square-planar structure is the preferred one when one oxygen vacancy is created. Thermodynamic analysis shows that TM-doped CeO2 surfaces contain oxygen defects under typical conditions of environmental catalysis. A case of practical importance is the facile lattice oxygen activation in Zr-doped CeO2(111), which benefits CO oxidation. The findings emphasize the origin of lattice oxygen activation and the preferred location of TM dopants in TM-ceria solid solution catalysts.展开更多
基金supported by the National Natural Science Foundation of China(10674042)Innovation Scientists and Technicians Troop Construction Projects of Henan Province,China(104200510014)~~
基金supported by the National Key R&D Program of China(2017YFB0602205,2016YFA0202803,2017YFA0303104)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB17020200)the National Natural Science Foundation of China(21473191,91545204)~~
文摘Ceria-based catalytic materials are known for their crystal-face-dependent catalytic properties.To obtain a molecular-level understanding of their surface chemistry,controlled synthesis of ceria with well-defined surface structures is required.We have thus studied the growth of CeOx nanostructures(NSs)and thin films on Pt(111).The strong metal-oxide interaction has often been invoked to explain catalytic processes over the Pt/CeOx catalysts.However,the Pt-CeOx interaction has not been understood at the atomic level.We show here that the interfacial interaction between Pt and ceria could indeed affect the surface structures of ceria,which could subsequently determine their catalytic chemistry.While ceria on Pt(111)typically exposes the CeO2(111)surface,we found that the structures of ceria layers with a thickness of three layers or less are highly dynamic and dependent on the annealing temperatures,owing to the electronic interaction between Pt and CeOx.A two-step kinetically limited growth procedure was used to prepare the ceria film that fully covers the Pt(111)substrate.For a ceria film of^3–4 monolayer(ML)thickness on Pt(111),annealing in ultrahigh vacuum(UHV)at 1000 K results in a surface of CeO2(100),stabilized by a c-Ce2O3(100)buffer layer.Further oxidation at 900 K transforms the surface of the CeO2(100)thin film into a hexagonal CeO2(111)surface.
基金supported by the National Natural Science Foundation of China(Grant Nos.11174070,51401078,and 11147006)the China Postdoctoral Science Foundation(Grant No.2012M521399)+2 种基金the Postdoctoral Research Sponsorship in Henan Province,China(Grant No.2011038)the Foundation for the Key Young Teachers of Henan Normal UniversityStart-up Foundation for Doctors of Henan Normal University,China
文摘To investigate the effects of chlorine on the Au/ceria catalysts,the adsorption of gold or chlorine and their coadsorpiton on the stoichiometric and partially reduced CeO2（111） surfaces are studied from the first principles.It is found that the adsorption of Au is significantly enhanced by the chlorine preadsorption on the stoichiometric CeO2（111） surface;while on the partially reduced CeO2（111） surface,the preadsorbed chlorine inhabits the oxygen vacancy（which is the preferred adsorption site for gold）,leading to a CeOCl phase and the dramatical weakening of the Au adsorption.Therefore,chlorine on the CeO2（111） surface can affect the Au adsorption thus the activity of the Au/CeO2 catalyst.
基金supported by The Netherlands Organization for Scientific Research(NWO)through a Vici grant and Nuffic fundingfunding from the European Union’s Horizon 2020 research and innovation programme under grant No.686086(Partial-PGMs)。
文摘Density functional theory calculations were carried out to investigate the influence of doping transition metal(TM) ions into the ceria surface on the activation of surface lattice oxygen atoms. For this purpose, the structure and stability of the most stable(111) surface termination of CeO2 modified by TM ions was determined. Except for Zr and Pt dopants that preserve octahedral oxygen coordination, the TM dopants prefer a square-planar coordination when substituting the surface Ce ions. The surface construction from octahedral to square-planar is facile for all TM dopants, except for Pt(1.14 e V) and Zr(square-planar coordination unstable). Typically, the ionic radius of tetravalent TM cations is much smaller than that of Ce4+, resulting a significant tensile-strained lattice and explaining the lowered oxygen vacancy formation energy. Except for Zr, the square-planar structure is the preferred one when one oxygen vacancy is created. Thermodynamic analysis shows that TM-doped CeO2 surfaces contain oxygen defects under typical conditions of environmental catalysis. A case of practical importance is the facile lattice oxygen activation in Zr-doped CeO2(111), which benefits CO oxidation. The findings emphasize the origin of lattice oxygen activation and the preferred location of TM dopants in TM-ceria solid solution catalysts.
