Epitaxiai CeO_2 thin films have ben grown on in situ (1102) sapphire subetrate by planar target rf mag-netron sputtering methed. The CeO_2 thin films have perfect (002) orientation with CeO_2(001)∥Al_2O_3(1102). The ...Epitaxiai CeO_2 thin films have ben grown on in situ (1102) sapphire subetrate by planar target rf mag-netron sputtering methed. The CeO_2 thin films have perfect (002) orientation with CeO_2(001)∥Al_2O_3(1102). The X-ray 2θ-θ diffraction, ω scan, Φ scan and electron channelling pattern (ECP) shown that thefilms liave high lattice perfection. The relation of growth conditions and film structure was also studied. Thespudering gas presure and subetrate temperature are the most important parameters preparing fer high qualitybeO_2 films.展开更多
The redox capacity of CeO2/Al2O3 thin film which was prepared by sol-gel method has been investigated by X-ray Photoelectron Spectrascopy (XPS). The results showed that the thin film was easier to be reduced and re-ox...The redox capacity of CeO2/Al2O3 thin film which was prepared by sol-gel method has been investigated by X-ray Photoelectron Spectrascopy (XPS). The results showed that the thin film was easier to be reduced and re-oxidized than pure CeO2 powder. The key role played by oxygen vacancies which were created from the interaction between CeO2 and Al,O, was also discussed.展开更多
Understanding how defect chemistry of oxide material influences the thermal stability of noble metal dopant ions plays an important role in designing high-performance heterogeneous catalytic systems.Here we use in-sit...Understanding how defect chemistry of oxide material influences the thermal stability of noble metal dopant ions plays an important role in designing high-performance heterogeneous catalytic systems.Here we use in-situ ambient-pressure X-ray photoemission spectroscopy(APXPS)to experimentally determine the role of grain boundary in the thermal stability of platinum doped cerium oxide(Pt/CeO_(2)).The grain boundaries were introduced in Pt/CeO_(2)thin films by pulsed laser deposition without significantly change of the surface microstructure.The defect level was tuned by the strain field obtained using a highly/low mismatched substrate.The Pt/CeO_(2)thin film models having well defined crystallographic properties but different grain boundary structural defect levels provide an ideal platform for exploring the evolution of Pt–O–Ce bond with changing the temperature in reducing conditions.We have direct demonstration and explanation of the role of Ce^(3+)induced by grain boundaries in enhancing Pt2+stability.We observe that the Pt^(2+)–O–Ce^(3+)bond provides an ideal coordinated site for anchoring of Pt^(2+)ions and limits the further formation of oxygen vacancies during the reduction with H_(2).Our findings demonstrate the importance of grain boundary in the atomic-scale design of thermally stable catalytic active sites.展开更多
A series of transition metals(Fe,Co,Ni,Cu,Cr and Mn)-doped CeO_(2)-TiO_(2) catalysts were prepared by the sol-gel method and applied for the catalytic removal of 1,2-dichloroethane(DCE) as a model for chlorinated VOCs...A series of transition metals(Fe,Co,Ni,Cu,Cr and Mn)-doped CeO_(2)-TiO_(2) catalysts were prepared by the sol-gel method and applied for the catalytic removal of 1,2-dichloroethane(DCE) as a model for chlorinated VOCs(CVOCs).The various characterization methods including X-ray diffraction(XRD),N_(2) adsorption-desorption,UV-Raman,NH_(3) temperature-programmed desorption(NH_(3)-TPD) and H_(2) temperature-programmed reduction(H_(2)-TPR) were utilized to investigate the physicochemical properties of the catalysts.The results show that doping Fe,Co,Ni or Mn can obviously promote the activity of CeO_(2)-TiO_(2) mixed oxides for DCE degradation,which is related to their improved texture properties,acid sites(especially for strong acidity) and low-temperature reducibility.Particularly,CeTi-Fe doped with moderate Fe exhibits excellent activity for 1,2-dichloroethane(DCE) degradation,giving a T_(90%) value as low as 250℃.More importantly,only trace chlorinated byproducts were produced during the low-temperature degradation of various CVOCs(dichloromethane(DCM),trichloroethylene(TCE) and chlorobenzene(CB)) over CeTi-Fe1/9 catalyst with high durability.展开更多
Sol-gel derived nanostructured CeO_2 film was deposited on glass substrate using by dip-coating technique with annealing at 650℃.X-ray diffraction（XRD）,scanning electron microscopy（SEM）,Fourier transform infrared...Sol-gel derived nanostructured CeO_2 film was deposited on glass substrate using by dip-coating technique with annealing at 650℃.X-ray diffraction（XRD）,scanning electron microscopy（SEM）,Fourier transform infrared （FTIR）,UV/vis and photoluminescence（PL） spectroscopy studies were employed to analyze the structural and optical properties of the sol-gel derived nanostructured CeO_2 film.The average crystallite size was estimated from the XRD pattern using by Scherrer equation as about 3-4 nm.An SEM micrograph shows that the film was porous in nature and crack free.The UV-visible absorption spectroscopic measurement results showed that the products had conspicuous quantum size effects.The absorption spectrum indicates that the sol-gel derived nanostructured CeO_2 film has a direct bandgap of 3.23 eV and the photoluminescence spectra of the film show a strong band at 378 nm：it may have a promising application as an optoelectronic material.展开更多
In this paper,the early stages of nucleation and photoirradiation growth of CeO_(2) thin films have been studied.Cyclic voltammetry,chronoamperometry and scanning electron microscopy were used to analyze the nucleatio...In this paper,the early stages of nucleation and photoirradiation growth of CeO_(2) thin films have been studied.Cyclic voltammetry,chronoamperometry and scanning electron microscopy were used to analyze the nucleation process of CeO_(2) thin films deposited on the anode with photo irradiation.Experimental results show that the anodic deposition process with photo illumination is controlled by diffusion.Compared with the dark state,photo illumination mainly contributed to increase the current density of the three-dimensional nucleation process,because photo illumination is helpful to create active sites and accelerate the nucleation progress on the surface that a thin ceria film has been formed.Two-dimensional nucleation process mainly exists within the initial 2 s,and then only three-dimensional instantaneous nucleation process continues,which may be the main reason why the thickness of the CeO_(2) film can continue to grow with photo illumination but not in the dark state.Increasing the deposition overpotential can promote two-dimensional nucleation and growth rate,whilst when the potential exceeds 0.65 V,three-dimensional current density decreases.The limiting factor at that time may be the diffusion rate of cerium ions in the solution towards the electrode substrate.展开更多
文摘Epitaxiai CeO_2 thin films have ben grown on in situ (1102) sapphire subetrate by planar target rf mag-netron sputtering methed. The CeO_2 thin films have perfect (002) orientation with CeO_2(001)∥Al_2O_3(1102). The X-ray 2θ-θ diffraction, ω scan, Φ scan and electron channelling pattern (ECP) shown that thefilms liave high lattice perfection. The relation of growth conditions and film structure was also studied. Thespudering gas presure and subetrate temperature are the most important parameters preparing fer high qualitybeO_2 films.
文摘The redox capacity of CeO2/Al2O3 thin film which was prepared by sol-gel method has been investigated by X-ray Photoelectron Spectrascopy (XPS). The results showed that the thin film was easier to be reduced and re-oxidized than pure CeO2 powder. The key role played by oxygen vacancies which were created from the interaction between CeO2 and Al,O, was also discussed.
基金The APXPS experiments were performed at BL02B01 of SSRF with the approval of the Proposal Assessing Committee of SiP.ME2 platform project(Proposal No.2019-SSRF-PT-011613)the Natural Science Foundation of China(No.11227902)the Shanghai Key Research Program(No.20ZR1436700).
文摘Understanding how defect chemistry of oxide material influences the thermal stability of noble metal dopant ions plays an important role in designing high-performance heterogeneous catalytic systems.Here we use in-situ ambient-pressure X-ray photoemission spectroscopy(APXPS)to experimentally determine the role of grain boundary in the thermal stability of platinum doped cerium oxide(Pt/CeO_(2)).The grain boundaries were introduced in Pt/CeO_(2)thin films by pulsed laser deposition without significantly change of the surface microstructure.The defect level was tuned by the strain field obtained using a highly/low mismatched substrate.The Pt/CeO_(2)thin film models having well defined crystallographic properties but different grain boundary structural defect levels provide an ideal platform for exploring the evolution of Pt–O–Ce bond with changing the temperature in reducing conditions.We have direct demonstration and explanation of the role of Ce^(3+)induced by grain boundaries in enhancing Pt2+stability.We observe that the Pt^(2+)–O–Ce^(3+)bond provides an ideal coordinated site for anchoring of Pt^(2+)ions and limits the further formation of oxygen vacancies during the reduction with H_(2).Our findings demonstrate the importance of grain boundary in the atomic-scale design of thermally stable catalytic active sites.
基金Project supported by the National Key Research and Development Program of China(2016YFC0204300)the National Natural Science Foundation of China(21477109)。
文摘A series of transition metals(Fe,Co,Ni,Cu,Cr and Mn)-doped CeO_(2)-TiO_(2) catalysts were prepared by the sol-gel method and applied for the catalytic removal of 1,2-dichloroethane(DCE) as a model for chlorinated VOCs(CVOCs).The various characterization methods including X-ray diffraction(XRD),N_(2) adsorption-desorption,UV-Raman,NH_(3) temperature-programmed desorption(NH_(3)-TPD) and H_(2) temperature-programmed reduction(H_(2)-TPR) were utilized to investigate the physicochemical properties of the catalysts.The results show that doping Fe,Co,Ni or Mn can obviously promote the activity of CeO_(2)-TiO_(2) mixed oxides for DCE degradation,which is related to their improved texture properties,acid sites(especially for strong acidity) and low-temperature reducibility.Particularly,CeTi-Fe doped with moderate Fe exhibits excellent activity for 1,2-dichloroethane(DCE) degradation,giving a T_(90%) value as low as 250℃.More importantly,only trace chlorinated byproducts were produced during the low-temperature degradation of various CVOCs(dichloromethane(DCM),trichloroethylene(TCE) and chlorobenzene(CB)) over CeTi-Fe1/9 catalyst with high durability.
文摘Sol-gel derived nanostructured CeO_2 film was deposited on glass substrate using by dip-coating technique with annealing at 650℃.X-ray diffraction（XRD）,scanning electron microscopy（SEM）,Fourier transform infrared （FTIR）,UV/vis and photoluminescence（PL） spectroscopy studies were employed to analyze the structural and optical properties of the sol-gel derived nanostructured CeO_2 film.The average crystallite size was estimated from the XRD pattern using by Scherrer equation as about 3-4 nm.An SEM micrograph shows that the film was porous in nature and crack free.The UV-visible absorption spectroscopic measurement results showed that the products had conspicuous quantum size effects.The absorption spectrum indicates that the sol-gel derived nanostructured CeO_2 film has a direct bandgap of 3.23 eV and the photoluminescence spectra of the film show a strong band at 378 nm：it may have a promising application as an optoelectronic material.
基金This work was supported by the National Natural Science Foundation of China(Nos.52001300,51771173,21171155 and 51471156).
文摘In this paper,the early stages of nucleation and photoirradiation growth of CeO_(2) thin films have been studied.Cyclic voltammetry,chronoamperometry and scanning electron microscopy were used to analyze the nucleation process of CeO_(2) thin films deposited on the anode with photo irradiation.Experimental results show that the anodic deposition process with photo illumination is controlled by diffusion.Compared with the dark state,photo illumination mainly contributed to increase the current density of the three-dimensional nucleation process,because photo illumination is helpful to create active sites and accelerate the nucleation progress on the surface that a thin ceria film has been formed.Two-dimensional nucleation process mainly exists within the initial 2 s,and then only three-dimensional instantaneous nucleation process continues,which may be the main reason why the thickness of the CeO_(2) film can continue to grow with photo illumination but not in the dark state.Increasing the deposition overpotential can promote two-dimensional nucleation and growth rate,whilst when the potential exceeds 0.65 V,three-dimensional current density decreases.The limiting factor at that time may be the diffusion rate of cerium ions in the solution towards the electrode substrate.
