The atomic structure of the active sites in Cu/CeO2 catalysts is intimately associated with the copper-ceria interaction. Both the shape of ceria and the loading of copper affect the chemical bonding of copper species...The atomic structure of the active sites in Cu/CeO2 catalysts is intimately associated with the copper-ceria interaction. Both the shape of ceria and the loading of copper affect the chemical bonding of copper species on ceria surfaces and the electronic and geometric character of the relevant interfaces. Nanostructured ceria, including particles(polyhedra), rods, and cubes, provides anchoring sites for the copper species. The atomic arrangements and chemical properties of the(111),(110) and(100) facets, preferentially exposed depending on the shape of ceria, govern the copper-ceria interactions and in turn determine their catalytic properties. Also, the metal loading significantly influences the dispersion of copper species on ceria with a specific shape, forming copper layers, clusters, and nanoparticles. Lower copper contents result in copper monolayers and/or bilayers while higher copper loadings lead to multi-layered clusters and faceted particles. The active sites are usually generated via interactions between the copper atoms in the metal species and the oxygen vacancies on ceria, which is closely linked to the number and density of surface oxygen vacancies dominated by the shape of ceria.展开更多
Electrochemical reduction of CO2 to multi-carbon products(e.g.,C2+ ,ethene,ethanol,etc.)not only effectively decreases the CO2 concentration in atmosphere but also shows great potential economic benefits due ...Electrochemical reduction of CO2 to multi-carbon products(e.g.,C2+ ,ethene,ethanol,etc.)not only effectively decreases the CO2 concentration in atmosphere but also shows great potential economic benefits due to these exploitable value-added products.The Cu-based catalysts have caught much attention in CO2 electroreduction due to the good selectivity to hydrocarbons products.However,designing appropriate Cu-based catalysts is desirable to further improve the energy efficiency and selectivity of specific C2+ product.In this review,primary pathways of CO2 electroreduction to C2+ products are first discussed to summarize the key elementary steps of C2+ products formation.Subsequently,various strategies of catalytic activity regulation of Cu-based catalysts are classified into geometric and electronic structures modification based on the inner correlation between these strategies and the mechanism of C2+ products formation.The review ends with a cross-scale perspective that links the selectivity enhancement of a specific C2+ product and the target design of Cu-based catalysts.展开更多
In this study,the promotional effect of Ce and Nb doping on Cu/TiO2 catalyst for diethylamine catalytic degradation was investigated.The activity tests reveal that the Ce and Nb modification can facilitate the risi...In this study,the promotional effect of Ce and Nb doping on Cu/TiO2 catalyst for diethylamine catalytic degradation was investigated.The activity tests reveal that the Ce and Nb modification can facilitate the rising of mineralization rate and N2 selectivity during diethylamine degradation,achieving over 90%mineralization rate at 250-450°C,along with N2 selectivity exceeding 80% within 300-400°C.Characterization results show that the co-addition of Ce and Nb induces strong interactions with Cu species and increases surface Brønsted acid sites.Crucially,the enhanced redox capability derived from interactions guarantees good catalytic activity and mineralization rate.Additionally,the increased Brønsted acidity from Nb doping can suppress the formation of NCO(a)species,resulting in less generation of NOx from NCO(a)oxidation.Moreover,the enhanced Brønsted acidity can promote the internal SCR reaction,which also reduces the NOx emission.This work could offer valuable insights for designing catalysts with superior catalytic performance for amine-like volatile organic compounds(VOCs)degradation.展开更多
CeO2 was synthesized via sol-gel process and used as supporter to prepare CuO/CeO2, Cu/CeO2 catalysts by impregnation method. The catalytic properties and characterization of CeO2, CuO/CeO2 and Cu/CeO2 catalysts were ...CeO2 was synthesized via sol-gel process and used as supporter to prepare CuO/CeO2, Cu/CeO2 catalysts by impregnation method. The catalytic properties and characterization of CeO2, CuO/CeO2 and Cu/CeO2 catalysts were examined by means of a microreactor-GC system, HRTEM, XRD, TPR and XPS techniques. The results show that CuO has not catalytic activity and the activity of CeO2 is quite low for CO oxidation. However, the catalytic activity of CuO/CeO2 and Cu/ CeO2 catalysts increases significantly. Furthermore, the activity of CuO/CeO2 is higher than that of Cu/CeO2 catalysts.展开更多
Direct synthesis of dimethyl carbonate(DMC)from CO2 is critical for achieving carbon neutrality,yet the sluggish formation and conversion of the key*CH₃OCOO intermediate-due to the difficulty of C-O coupling-limit ...Direct synthesis of dimethyl carbonate(DMC)from CO2 is critical for achieving carbon neutrality,yet the sluggish formation and conversion of the key*CH₃OCOO intermediate-due to the difficulty of C-O coupling-limit high DMC yields.Herein,we developed a boric acid-assisted recrystallization strategy to fabricate grain-boundary-rich CeO2 hollow nanospheres,which serve as an efficient catalyst for CO2 to DMC synthesis.The introduction of grain-boundary(GBs)induced the electron redistribution,which led a decrease in the electron density of bulk Ce ions and created a localized electron-rich region at homogeneous interface.This unique electronic landscape promoted reactive methoxy formation and stronger CO2 adsorption,thereby enabling more efficient coupling of*CH3O and*CO2 to form the*CH3OCOO.Concurrently,the enhanced CO2 adsorption facilitated the dissociation of*CH3OCOO and subsequent DMC formation.As a result,the 4%BCeO2-GBs achieved an advantageous DMC yield of 19.8 mmol/g.In the assistance of dehydrating agent,the catalyst delivered a remarkable 264.2 mmol/g DMC yield and 7.12%methanol conversion,which was 32 times higher than commercial CeO2.This study elucidated the intrinsic mechanisms governing*CH3OCOO intermediate behavior and offers valuable guidance for CO2 converting into high-value organic chemicals.展开更多
The reduction of carbon emissions in the steel industry is a significant challenge,and utilizing CO2 from carbon intensive steel industry off-gases for methanol production is a promising strategy for decarbonizatio...The reduction of carbon emissions in the steel industry is a significant challenge,and utilizing CO2 from carbon intensive steel industry off-gases for methanol production is a promising strategy for decarbonization.However,steelwork off-gases typically contain various impurities,including H2S,which can deactivate commercial methanol synthesis catalysts,Cu/ZnO/Al2O3(CZA).Reverse water-gas shift(RWGS)reaction is the predominant side reaction in CO2 hydrogenation to methanol which can occur at ambient pressure,enabling the decouple of RWGS from methanol production at high pressure.Then,a series of activated CZA catalysts has been in-situ pretreated in 400 ppm H2S/Ar at 250℃and tested for both RWGS reaction at ambient pressure and CO2 hydrogenation to methanol at high pressure.An innovative decoupling strategy was employed to isolate the RWGS reaction from the methanol synthesis process,enabling the investigation of the evolution of active site structures and the poisoning mechanism through elemental analysis,X-ray Diffraction,X-ray Photoelectron Spectroscopy,Fourier Transform Infrared Spectroscopy,Temperature Programmed Reduction and CO2 Temperature Programmed Desorption.The results indicate that there are different dynamic migration behaviors of ZnOx in the two reaction systems,leading to different poisoning mechanisms.These interesting findings are beneficial to develop sulfur resistant and durable highly efficient catalysts for CO2 hydrogenation to methanol,promoting the carbon emission reduction in steel industry.展开更多
Comprehensive analysis of the connection be-tween surface metal species and the mechanism of hydrogen(H2)generation on TiO2provides important new information for the develop-ment of more effective catalysts for ...Comprehensive analysis of the connection be-tween surface metal species and the mechanism of hydrogen(H2)generation on TiO2provides important new information for the develop-ment of more effective catalysts for H2 produc-tion.We have systematically investigated the mechanism of catalytic H2 generation on the Cu10/TiO2,Au10/TiO2,Au8Cu2/TiO2and Cu1/Au8Cu2/TiO2surfaces using density func-tional theory.Our results demonstrate an O-Hδ+···Hδ−-M type transition state for H2 production,and the Au8Cu2(0.54 eV)bimetal-lic cluster catalyst exhibits more activity in comparison to the Cu10(0.63 eV)and Au10(0.88 eV)cluster catalysts on the TiO2surface.On the Cu1/Au8Cu2/TiO2surface,we found that Au8Cu2clusters act as electron donors,while Cu single atom acts as an electron acceptor.Therefore,the Au8Cu2bimetallic catalyst has a low energy barrier(0.58 eV)in the reductive reaction of H2 production in water,but Cu single atom as the catalytic center has a higher en-ergy barrier(1.49 eV).This implies that bimetallic catalysts may be able to catalyze the wa-ter dehydrogenation reaction more successfully,which would be important knowledge for comprehending and refining the photocatalytic H2 generation process.展开更多
The oxidative properties and characterization of CuO, CeO 2 and CuO/CeO 2 cata lysts were examined by means of a CO micro-reactor GC system, TPR, XPS and X-r ay diffraction Rietveld methods. The results show that eith...The oxidative properties and characterization of CuO, CeO 2 and CuO/CeO 2 cata lysts were examined by means of a CO micro-reactor GC system, TPR, XPS and X-r ay diffraction Rietveld methods. The results show that either CuO or CeO 2 ac tivity is quite low for CO oxidation. However, when CuO and CeO 2 are mixed, the oxidative activity of the catalyst increases significantly, probably owing to the valency status of copper species (Cu 2+ and Cu+) on the CeO 2 surfa ce, the dispersion and reducibility. XPS surface analysis shows that CuO loading is very important in forming of either Cu 2+ or Cu+. Rietveld analysis s hows that some CuO, which has smaller ion radius than Ce 4+, enters the Ce O 2 lattice after CuO and CeO 2 are mixed. When the CuO loading reaches 5.0%, the size of CuO crystals is a minimum (6.1 nm) and the micro-strain value i s a maximum (2.86×10 -3), resulting in high surface energy and the best ac tivity for CO oxidation.展开更多
The CuO/CeO2 catalysts were investigated by means of X-ray diffraction (XRD), laser Raman spectroscopy (LRS), X-ray photoelectronic spectroscopy (XPS), temperature-programmed reduction (TPR), in situ Fourier t...The CuO/CeO2 catalysts were investigated by means of X-ray diffraction (XRD), laser Raman spectroscopy (LRS), X-ray photoelectronic spectroscopy (XPS), temperature-programmed reduction (TPR), in situ Fourier transform infrared spectroscopy (FTIR) and NO+CO reaction. The results revealed that the low temperature (〈150℃) catalytic performances were enhanced for CO pretreated samples. During CO pretreatment, the surface Cu+/Cu0 and oxygen vacancies on ceria surface were present. The low va- lence copper species activated the adsorbed CO and surface oxygen vacancies facilitated the NO dissociation. These effects in turn led to higher activities of CuO/CeO2 for NO reduction. The current study provided helpful understandings of active sites and reaction mechanism in NO+CO reaction.展开更多
The nanometer CeO2 powder was prepared by the method of microwave-assisted heating hydrolysis,and the nanometer CeO2-supported or ordinary CeO2-supported vanadia catalysts with different vanadium loadings(atomic ratio...The nanometer CeO2 powder was prepared by the method of microwave-assisted heating hydrolysis,and the nanometer CeO2-supported or ordinary CeO2-supported vanadia catalysts with different vanadium loadings(atomic ratios:100V/Ce=0.1,1,4,10,and 20) were prepared by an incipient-wetness impregnation method.Spectroscopic techniques(XRD,FT-IR,Raman and UV-Vis DRS) were utilized to characterize the structures of VOx/CeO2 catalysts.The results showed that the structures of CeO2-supported vanadium oxide catalysts de...展开更多
This paper presented a study on the role of yttrium addition to CuO/CeO2 catalyst for water-gas shift reaction. A single-step co-precipitation method was used for preparation of a series of yttrium doped CuO/CeO2 cata...This paper presented a study on the role of yttrium addition to CuO/CeO2 catalyst for water-gas shift reaction. A single-step co-precipitation method was used for preparation of a series of yttrium doped CuO/CeO2 catalysts with yttrium content in the range of 0-5wt.%. Properties of the obtained samples were characterized and analyzed by X-ray diffraction (XRD), Raman spectroscopy, H2-TPR, cyclic voltammetry (CV) and the BET method. The results revealed that catalytic activity was increased with the yttrium content at first, but then decreased with the further increase of yttrium content. Herein, CuO/CeO2 catalyst doped with 2wt.% of yttrium showed the highest catalytic activity (CO conversion reaches 93.4% at 250 ℃) and thermal stability for WGS reaction. The catalytic activity was correlated with the surface area, the area of peak γ of H2-TPR profile (i.e., the reduction of surface copper oxide (crystalline forms) interacted with surface oxygen vacancies on ceria), and the area of peak C2 and A1 (Cu^0→←Cu^2+ in cyclic voltammetry process), respectively. Besides, Raman spectra provided evidences for a synergistic Cu-Ovacancy interaction, and it was indicated that doping yttrium may facilitate the formation of oxygen vacancies on ceria.展开更多
Cu/CeO2-ZrO2 catalysts for water-gas shift(WGS)reaction were prepared with co-precipitation method,and the influence of ZrO2 content on the catalytic structure and properties was investigated by the techniques of N2 p...Cu/CeO2-ZrO2 catalysts for water-gas shift(WGS)reaction were prepared with co-precipitation method,and the influence of ZrO2 content on the catalytic structure and properties was investigated by the techniques of N2 physical adsorption analysis,XRD and H2-TPR.The results indicate that the BET surface areas of the catalysts are increased in varying degrees due to the presence of ZrO2.With increasing ZrO2 content,the pore size distribution is centered on 1.9 nm.ZrO2 can efficiently restrain the growth of Cu crystal particles.The appropriate amount of ZrO2 in the Cu/CeO2 catalysts can help the catalyst keep better copper dispersion in the WGS reaction,which can lead to both higher catalytic activity and better thermal stability.When ZrO2 content is 10%(atom fraction),Cu/CeO2-Zr02 catalyst reaches a CO conversion rate of 73.7%at the reaction temperature of 200℃.展开更多
Three series of CeO2/CuO samples were prepared by impregnation method and characterized by XRD, N2 adsorption-desorption, temperatureprogrammed reduction (TPR), XPS and TEM techniques. In comparison with the samples...Three series of CeO2/CuO samples were prepared by impregnation method and characterized by XRD, N2 adsorption-desorption, temperatureprogrammed reduction (TPR), XPS and TEM techniques. In comparison with the samples prepared with CuO as initial support, the samples with Cu(OH)2 as initial support have higher reducibilities and smaller relative TPR peak areas, and also larger specific surface areas at calcina- tion temperatures of 400 ℃--600 ℃. As a result, Cu(OH)2 is better than CuO as initial support for preferential oxidation of CO in excess H2 (CO-PROX). The best catalytic performance was achieved on the sample calcined at 600 ℃ and with an atomic ratio of Ce/Cu at 40%. XPS analyses indicate that more interface linkages Ce-O-Cu could be formed when it was calcined at 600 ℃. And the atomic ratio of Ce/Cu at 40% led to a proper reducibility for the sample as illustrated by the TPR measurements.展开更多
In this work, we have reported the influence of the addition of base (KOH) on the physicochemical property of ceria synthesized by alcohothermal process, and the alcohothermal mechanism was also put forward. Further...In this work, we have reported the influence of the addition of base (KOH) on the physicochemical property of ceria synthesized by alcohothermal process, and the alcohothermal mechanism was also put forward. Furthermore, the prepared CeO2 was used as the support to prepare CuO/CeO2 catalysts via the wet impregnation method. The samples were characterized by N2 adsorption-desorption, X-ray powder diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and temperatureprogrammed reduction by H2 (H2-TPR). The catalytic properties of the CuO/CeO2 catalysts for lowtemperature CO oxidation were studied using a microreactor-GC system. The crystal size of CeO2-A was much smaller than that of CeO2-B, and the corresponding copper oxide catalysts exhibited higher catalytic activity than that of the CeO2-B-supported catalysts under the same reaction conditions. The alcohothermal mechanism indicated that KOH plays a key role in determining the physicochemical and catalytic properties of ceria-based materials.展开更多
摘要The atomic structure of the active sites in Cu/CeO2 catalysts is intimately associated with the copper-ceria interaction. Both the shape of ceria and the loading of copper affect the chemical bonding of copper species on ceria surfaces and the electronic and geometric character of the relevant interfaces. Nanostructured ceria, including particles(polyhedra), rods, and cubes, provides anchoring sites for the copper species. The atomic arrangements and chemical properties of the(111),(110) and(100) facets, preferentially exposed depending on the shape of ceria, govern the copper-ceria interactions and in turn determine their catalytic properties. Also, the metal loading significantly influences the dispersion of copper species on ceria with a specific shape, forming copper layers, clusters, and nanoparticles. Lower copper contents result in copper monolayers and/or bilayers while higher copper loadings lead to multi-layered clusters and faceted particles. The active sites are usually generated via interactions between the copper atoms in the metal species and the oxygen vacancies on ceria, which is closely linked to the number and density of surface oxygen vacancies dominated by the shape of ceria.
基金financially supported by the project Natural Science Foundation of Jiangxi Provincial(Grant Nos.20252BAC200212 and 20252BAC250027)the Fundamental Research Funds for the Cultivation of Early Career Young Scientific and Technological Talents of Jiangxi Province(Grant Nos.20252BEJ730203,20252BEJ730205,and 20224ACB203010)+2 种基金Doctor's Starting Research Foundation of Jiangxi University of Science and Technology(Grant No.205200100778)the National Natural Science Foundation of China(Grant Nos.22572077,22162012 and 22202089)the Natural Science Foundation of Jiangxi Province for Distinguished Young Scholars(Grant No.20224ACB213005)。
摘要Electrochemical reduction of CO2 to multi-carbon products(e.g.,C2+ ,ethene,ethanol,etc.)not only effectively decreases the CO2 concentration in atmosphere but also shows great potential economic benefits due to these exploitable value-added products.The Cu-based catalysts have caught much attention in CO2 electroreduction due to the good selectivity to hydrocarbons products.However,designing appropriate Cu-based catalysts is desirable to further improve the energy efficiency and selectivity of specific C2+ product.In this review,primary pathways of CO2 electroreduction to C2+ products are first discussed to summarize the key elementary steps of C2+ products formation.Subsequently,various strategies of catalytic activity regulation of Cu-based catalysts are classified into geometric and electronic structures modification based on the inner correlation between these strategies and the mechanism of C2+ products formation.The review ends with a cross-scale perspective that links the selectivity enhancement of a specific C2+ product and the target design of Cu-based catalysts.
基金Project supported by the National Natural Science Foundation of China (22076164,22276162,22306072)China Postdoctoral Science Foundation (2023M731441)Young Talent Fund of Jiaxing Science and Technology Project (2023AY40030)
摘要In this study,the promotional effect of Ce and Nb doping on Cu/TiO2 catalyst for diethylamine catalytic degradation was investigated.The activity tests reveal that the Ce and Nb modification can facilitate the rising of mineralization rate and N2 selectivity during diethylamine degradation,achieving over 90%mineralization rate at 250-450°C,along with N2 selectivity exceeding 80% within 300-400°C.Characterization results show that the co-addition of Ce and Nb induces strong interactions with Cu species and increases surface Brønsted acid sites.Crucially,the enhanced redox capability derived from interactions guarantees good catalytic activity and mineralization rate.Additionally,the increased Brønsted acidity from Nb doping can suppress the formation of NCO(a)species,resulting in less generation of NOx from NCO(a)oxidation.Moreover,the enhanced Brønsted acidity can promote the internal SCR reaction,which also reduces the NOx emission.This work could offer valuable insights for designing catalysts with superior catalytic performance for amine-like volatile organic compounds(VOCs)degradation.
基金Projected supported by the National Natural Science Foundation of China (20271028) and Tianjin Natural Science Foundation(033602511)
摘要CeO2 was synthesized via sol-gel process and used as supporter to prepare CuO/CeO2, Cu/CeO2 catalysts by impregnation method. The catalytic properties and characterization of CeO2, CuO/CeO2 and Cu/CeO2 catalysts were examined by means of a microreactor-GC system, HRTEM, XRD, TPR and XPS techniques. The results show that CuO has not catalytic activity and the activity of CeO2 is quite low for CO oxidation. However, the catalytic activity of CuO/CeO2 and Cu/ CeO2 catalysts increases significantly. Furthermore, the activity of CuO/CeO2 is higher than that of Cu/CeO2 catalysts.
摘要Direct synthesis of dimethyl carbonate(DMC)from CO2 is critical for achieving carbon neutrality,yet the sluggish formation and conversion of the key*CH₃OCOO intermediate-due to the difficulty of C-O coupling-limit high DMC yields.Herein,we developed a boric acid-assisted recrystallization strategy to fabricate grain-boundary-rich CeO2 hollow nanospheres,which serve as an efficient catalyst for CO2 to DMC synthesis.The introduction of grain-boundary(GBs)induced the electron redistribution,which led a decrease in the electron density of bulk Ce ions and created a localized electron-rich region at homogeneous interface.This unique electronic landscape promoted reactive methoxy formation and stronger CO2 adsorption,thereby enabling more efficient coupling of*CH3O and*CO2 to form the*CH3OCOO.Concurrently,the enhanced CO2 adsorption facilitated the dissociation of*CH3OCOO and subsequent DMC formation.As a result,the 4%BCeO2-GBs achieved an advantageous DMC yield of 19.8 mmol/g.In the assistance of dehydrating agent,the catalyst delivered a remarkable 264.2 mmol/g DMC yield and 7.12%methanol conversion,which was 32 times higher than commercial CeO2.This study elucidated the intrinsic mechanisms governing*CH3OCOO intermediate behavior and offers valuable guidance for CO2 converting into high-value organic chemicals.
基金supported by the National Natural Science Foundation of China(Nos.22276060 and 21976059)Guangdong Basic and Applied Basic Research Foundation(No.2024A1515012636)China Scholarship Council Scholarship(No.201906155006)。
摘要The reduction of carbon emissions in the steel industry is a significant challenge,and utilizing CO2 from carbon intensive steel industry off-gases for methanol production is a promising strategy for decarbonization.However,steelwork off-gases typically contain various impurities,including H2S,which can deactivate commercial methanol synthesis catalysts,Cu/ZnO/Al2O3(CZA).Reverse water-gas shift(RWGS)reaction is the predominant side reaction in CO2 hydrogenation to methanol which can occur at ambient pressure,enabling the decouple of RWGS from methanol production at high pressure.Then,a series of activated CZA catalysts has been in-situ pretreated in 400 ppm H2S/Ar at 250℃and tested for both RWGS reaction at ambient pressure and CO2 hydrogenation to methanol at high pressure.An innovative decoupling strategy was employed to isolate the RWGS reaction from the methanol synthesis process,enabling the investigation of the evolution of active site structures and the poisoning mechanism through elemental analysis,X-ray Diffraction,X-ray Photoelectron Spectroscopy,Fourier Transform Infrared Spectroscopy,Temperature Programmed Reduction and CO2 Temperature Programmed Desorption.The results indicate that there are different dynamic migration behaviors of ZnOx in the two reaction systems,leading to different poisoning mechanisms.These interesting findings are beneficial to develop sulfur resistant and durable highly efficient catalysts for CO2 hydrogenation to methanol,promoting the carbon emission reduction in steel industry.
基金supported by the National Natural Science Foundation of China(No.22473107)。
摘要Comprehensive analysis of the connection be-tween surface metal species and the mechanism of hydrogen(H2)generation on TiO2provides important new information for the develop-ment of more effective catalysts for H2 produc-tion.We have systematically investigated the mechanism of catalytic H2 generation on the Cu10/TiO2,Au10/TiO2,Au8Cu2/TiO2and Cu1/Au8Cu2/TiO2surfaces using density func-tional theory.Our results demonstrate an O-Hδ+···Hδ−-M type transition state for H2 production,and the Au8Cu2(0.54 eV)bimetal-lic cluster catalyst exhibits more activity in comparison to the Cu10(0.63 eV)and Au10(0.88 eV)cluster catalysts on the TiO2surface.On the Cu1/Au8Cu2/TiO2surface,we found that Au8Cu2clusters act as electron donors,while Cu single atom acts as an electron acceptor.Therefore,the Au8Cu2bimetallic catalyst has a low energy barrier(0.58 eV)in the reductive reaction of H2 production in water,but Cu single atom as the catalytic center has a higher en-ergy barrier(1.49 eV).This implies that bimetallic catalysts may be able to catalyze the wa-ter dehydrogenation reaction more successfully,which would be important knowledge for comprehending and refining the photocatalytic H2 generation process.
摘要The oxidative properties and characterization of CuO, CeO 2 and CuO/CeO 2 cata lysts were examined by means of a CO micro-reactor GC system, TPR, XPS and X-r ay diffraction Rietveld methods. The results show that either CuO or CeO 2 ac tivity is quite low for CO oxidation. However, when CuO and CeO 2 are mixed, the oxidative activity of the catalyst increases significantly, probably owing to the valency status of copper species (Cu 2+ and Cu+) on the CeO 2 surfa ce, the dispersion and reducibility. XPS surface analysis shows that CuO loading is very important in forming of either Cu 2+ or Cu+. Rietveld analysis s hows that some CuO, which has smaller ion radius than Ce 4+, enters the Ce O 2 lattice after CuO and CeO 2 are mixed. When the CuO loading reaches 5.0%, the size of CuO crystals is a minimum (6.1 nm) and the micro-strain value i s a maximum (2.86×10 -3), resulting in high surface energy and the best ac tivity for CO oxidation.
基金supported by National Basic Research Program of China(2010CB732300)National Natural Science Foundation of China(21273110,20973091)Natural Science Foundation for the Youth(21203091)
摘要The CuO/CeO2 catalysts were investigated by means of X-ray diffraction (XRD), laser Raman spectroscopy (LRS), X-ray photoelectronic spectroscopy (XPS), temperature-programmed reduction (TPR), in situ Fourier transform infrared spectroscopy (FTIR) and NO+CO reaction. The results revealed that the low temperature (〈150℃) catalytic performances were enhanced for CO pretreated samples. During CO pretreatment, the surface Cu+/Cu0 and oxygen vacancies on ceria surface were present. The low va- lence copper species activated the adsorbed CO and surface oxygen vacancies facilitated the NO dissociation. These effects in turn led to higher activities of CuO/CeO2 for NO reduction. The current study provided helpful understandings of active sites and reaction mechanism in NO+CO reaction.
基金supported by the National Natural Science Foundation of China (20803093,20833011,20525621)the Doctor Select Foundation for the University of State Education Ministry (200804251016)+1 种基金the Beijing Outstanding Ph.D.Thesis Foundation (YB 20091141401)the Hi-Tech Research and Development Program (863) of China (SQ2009AA06Z3488052)
摘要The nanometer CeO2 powder was prepared by the method of microwave-assisted heating hydrolysis,and the nanometer CeO2-supported or ordinary CeO2-supported vanadia catalysts with different vanadium loadings(atomic ratios:100V/Ce=0.1,1,4,10,and 20) were prepared by an incipient-wetness impregnation method.Spectroscopic techniques(XRD,FT-IR,Raman and UV-Vis DRS) were utilized to characterize the structures of VOx/CeO2 catalysts.The results showed that the structures of CeO2-supported vanadium oxide catalysts de...
基金supported by the National Natural Science Foundation of China (20771025)A-type Science and Technology Projects of Fujian Provincial Department of Education (JA08021)
摘要This paper presented a study on the role of yttrium addition to CuO/CeO2 catalyst for water-gas shift reaction. A single-step co-precipitation method was used for preparation of a series of yttrium doped CuO/CeO2 catalysts with yttrium content in the range of 0-5wt.%. Properties of the obtained samples were characterized and analyzed by X-ray diffraction (XRD), Raman spectroscopy, H2-TPR, cyclic voltammetry (CV) and the BET method. The results revealed that catalytic activity was increased with the yttrium content at first, but then decreased with the further increase of yttrium content. Herein, CuO/CeO2 catalyst doped with 2wt.% of yttrium showed the highest catalytic activity (CO conversion reaches 93.4% at 250 ℃) and thermal stability for WGS reaction. The catalytic activity was correlated with the surface area, the area of peak γ of H2-TPR profile (i.e., the reduction of surface copper oxide (crystalline forms) interacted with surface oxygen vacancies on ceria), and the area of peak C2 and A1 (Cu^0→←Cu^2+ in cyclic voltammetry process), respectively. Besides, Raman spectra provided evidences for a synergistic Cu-Ovacancy interaction, and it was indicated that doping yttrium may facilitate the formation of oxygen vacancies on ceria.
基金supported by the National Natural Science Foundation of China(20271012)Project for Science and Technology ofFujian Province(2002H026)
摘要Cu/CeO2-ZrO2 catalysts for water-gas shift(WGS)reaction were prepared with co-precipitation method,and the influence of ZrO2 content on the catalytic structure and properties was investigated by the techniques of N2 physical adsorption analysis,XRD and H2-TPR.The results indicate that the BET surface areas of the catalysts are increased in varying degrees due to the presence of ZrO2.With increasing ZrO2 content,the pore size distribution is centered on 1.9 nm.ZrO2 can efficiently restrain the growth of Cu crystal particles.The appropriate amount of ZrO2 in the Cu/CeO2 catalysts can help the catalyst keep better copper dispersion in the WGS reaction,which can lead to both higher catalytic activity and better thermal stability.When ZrO2 content is 10%(atom fraction),Cu/CeO2-Zr02 catalyst reaches a CO conversion rate of 73.7%at the reaction temperature of 200℃.
摘要Three series of CeO2/CuO samples were prepared by impregnation method and characterized by XRD, N2 adsorption-desorption, temperatureprogrammed reduction (TPR), XPS and TEM techniques. In comparison with the samples prepared with CuO as initial support, the samples with Cu(OH)2 as initial support have higher reducibilities and smaller relative TPR peak areas, and also larger specific surface areas at calcina- tion temperatures of 400 ℃--600 ℃. As a result, Cu(OH)2 is better than CuO as initial support for preferential oxidation of CO in excess H2 (CO-PROX). The best catalytic performance was achieved on the sample calcined at 600 ℃ and with an atomic ratio of Ce/Cu at 40%. XPS analyses indicate that more interface linkages Ce-O-Cu could be formed when it was calcined at 600 ℃. And the atomic ratio of Ce/Cu at 40% led to a proper reducibility for the sample as illustrated by the TPR measurements.
摘要In this work, we have reported the influence of the addition of base (KOH) on the physicochemical property of ceria synthesized by alcohothermal process, and the alcohothermal mechanism was also put forward. Furthermore, the prepared CeO2 was used as the support to prepare CuO/CeO2 catalysts via the wet impregnation method. The samples were characterized by N2 adsorption-desorption, X-ray powder diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and temperatureprogrammed reduction by H2 (H2-TPR). The catalytic properties of the CuO/CeO2 catalysts for lowtemperature CO oxidation were studied using a microreactor-GC system. The crystal size of CeO2-A was much smaller than that of CeO2-B, and the corresponding copper oxide catalysts exhibited higher catalytic activity than that of the CeO2-B-supported catalysts under the same reaction conditions. The alcohothermal mechanism indicated that KOH plays a key role in determining the physicochemical and catalytic properties of ceria-based materials.