Sulfation treatment has been widely used to promote the catalytic performance of ceria(CeO_(2))based catalysts for the selective catalytic reduction of NO by NH_(3)(NH_(3)-SCR of NO).Praseodymium oxide(PrO_(x)),anothe...Sulfation treatment has been widely used to promote the catalytic performance of ceria(CeO_(2))based catalysts for the selective catalytic reduction of NO by NH_(3)(NH_(3)-SCR of NO).Praseodymium oxide(PrO_(x)),another commonly used rare earth material with similar structural properties as CeO_(2),also shows satistactory redox properties due to the facile redox cycle of Pr^(3+)■Pr^(4+).In this work,gas phase sulfation treatment with varied duration was performed on PrO_(x) at 200℃,and the NH_(3)-SCR activity of sulfated PrO_(x) was evaluated.Based on the results of systematic characterizations(e.g.,N_(2)-physisorption,NH_(3) oxidation,NO oxidation,in situ diffuse Fourier transform infrared spectroscopy),it is revealed that the catalytic performance of sulfated PrO_(x)is highly dependent on the sulfation time(or the amount of sulfate species deposited on PrO_(x)),which has a significant impact on the competitive reaction between NH_(3) oxidation and NH_(3)-SCR of NO,thus determining the NH_(3)-SCR activity of PrO_(x).This work provides new insight into tuning the interaction between PrO_(x) surface and reactants(NO,NH_(3))via sulfation treatment,which cam guide the design and application of PrO_(x)based catalysts for NH_(3)-SCR of NO in the future.展开更多
CeO_(2)/TiO_(2)(denoted as Ce Ti) catalysts obtained by solid-phase impregnation behaved better in lowtemperature selective catalytic reduction of NO_(x)with NH_(3)(NH_(3)-SCR) than that by conventional wet impregnati...CeO_(2)/TiO_(2)(denoted as Ce Ti) catalysts obtained by solid-phase impregnation behaved better in lowtemperature selective catalytic reduction of NO_(x)with NH_(3)(NH_(3)-SCR) than that by conventional wet impregnation.To explore the main factors for activity distinction,the texture property,CeO_(2)dispersion and structure changes of TiO_(2)were comprehensively analyzed.It was found that surface changes of TiO_(2)had a significant impact on the improved activity.From results of inductively coupled plasma atomic emission spectrometer (ICP-AES),diffuse reflectance UV-vis spectroscopy (UV-vis-DRS) and Raman,it was inferred that Ce ions were partially incorporated into TiO_(2)lattice,accompanied with the formation of defects and vacancies during solid-phase impregnation.Accordingly,Ce Ti catalysts from solid-phase impregnation exhibited superiority in adsorption and activation of reactants.Further result from monitoring the preparation process indicated that the evolved NO played an important role in promoting Ce doping through depriving oxygen atoms on TiO_(2)surface.The interaction between Ce and Ti was enhanced.The catalyst performed better in NH_(3)-SCR,especially at low temperature,which testified the solid-phase impregnation could be an effective method to modulate interface structure for designing efficient catalyst.展开更多
A simple strategy of Cu modification was proposed to broaden the operation temperature window for NbCe catalyst.The best catalyst Cu0.010/Nb1Ce3 presented over 90%NO conversion in a wide temperature range of 200-400℃...A simple strategy of Cu modification was proposed to broaden the operation temperature window for NbCe catalyst.The best catalyst Cu0.010/Nb1Ce3 presented over 90%NO conversion in a wide temperature range of 200-400℃and exhibited an excellent H_(2)O or/and SO_(2) resistance at 275℃.To understand the promotional mechanism of Cu modification,the correlation among the"activity-structure-property"were tried to establish systematically.Cu species highly dispersed on NbCe catalyst to serve as the active component.The strong interaction among Cu,Nb and Ce promoted the emergence of NbO4 and induced more Bronsted acid sites.And Cu modification obviously enhanced the redox behavior of the NbCe catalyst.Besides,EPR probed the Cu species exited in the form of monomeric and dimeric Cu^(2+),the isolated Cu^(2+)acted as catalytic active sites to promote the reaction:Cu^(2+)-NO_(3)^(-)+NO(g)→Cu^(2+)-NO_(2)^(-)+NO_(2)(g).Then the generated NO_(2) would accelerate the fast-SCR reaction process and thus facilitated the lowtemperature deNO_(x) efficiency.Moreover,surface nitrates became unstable and easy to decompose after Cu modification,thus providing additional adsorption and activation sites for NH3,and ensuring the improvement of catalytic activity at high temperature.Since the NH3-SCR reaction followed by E-R reaction pathway efficaciously over Cu_(0.010)/Nb_(1)Ce_(3) catalyst,the excellent H_(2)O and SO_(2) resistance was as expected.展开更多
Active species loss owing to reactant stream washing is a general problem which industrial catalysts suffer from.In case of catalysts synthesized by co-precipitation method,which have active species unused in bulk pha...Active species loss owing to reactant stream washing is a general problem which industrial catalysts suffer from.In case of catalysts synthesized by co-precipitation method,which have active species unused in bulk phase,can be regenerated by a simple thermal treatment that leads to active species in bulk phase migration to surface of the deactivated catalysts.In this work,the influence of regeneration temperature was investigated by employing ammonium hydroxide washing to simulate reactant stream washing of CeCoxO2 catalysts for NO+CO reaction.It is found that the deactivated catalyst can be regenerated by simple thermal treatment and increasing calcination temperature could accelerate the Co species migration from the bulk phase to surface of catalysts.展开更多
In this study,a series of Mn-Ce/Al_(2)O_(3) catalysts was prepared by different methods of depositionprecipitation(MnCeAl-DP),impregnation(MnCeAl-IM) and citric acid(MnCeAl-CA),and the distinct effect of preparation m...In this study,a series of Mn-Ce/Al_(2)O_(3) catalysts was prepared by different methods of depositionprecipitation(MnCeAl-DP),impregnation(MnCeAl-IM) and citric acid(MnCeAl-CA),and the distinct effect of preparation methods on NO_(x) removal performance at low temperature was explored.Results show that MnCeAl-DP exhibits not only the best activity but also the highest resistance against SO_(2)/H_(2)O.With the assistance of comprehensive characterizations from scanning electron microscopy(SEM),Brunauer-Emmett-Teller(BET),X-ray diffraction(XRD),H_(2)-temperature programmed reduction(H_(2)-TPR),NH_(3)-te mperature programmed deso rption(NH_(3)-TPD),and X-ray photoelectron spectroscopy(XPS),it is revealed that the MnCeAl-DP sample owns admired features of large surface area and pore volume,enriched Mn^(4+) and chemisorbed oxygen species originating from enhanced interaction between MnO_x and CeO_(2),as well as improved adsorption capacity to NH_(3) and NO.All these factors contribute to activity enhancement.Further in-situ DRIFTS studies reveal that the improvement of NH_(3)-SCR performance over MnCeAI-DP is related to the formation of abundant nitrate species,which is beneficial to the "NH_(4)NO_(3)" reaction pathway and thus enhances low-temperature activity.展开更多
Pt_(3)Ni alloy structure is an effective strategy to accelerate ethanol oxidation reaction(EOR),while the stability in acid electrolyte is the fatal weakness and the current density still needs to be enhanced.Herein,u...Pt_(3)Ni alloy structure is an effective strategy to accelerate ethanol oxidation reaction(EOR),while the stability in acid electrolyte is the fatal weakness and the current density still needs to be enhanced.Herein,ultralong Pt_(3)Ni nanowires tailored by trace Mo(Mo/Pt_(3)Ni NWs)were successfully synthesized by surfactant free method.The specific activity of the optimized catalyst was 2.66 mA·cm^(-2),which is approximately 2.16 and 4.6-fold that of Pt_(3)Ni NWs and commercial Pt/C catalyst,respectively.Most importantly,the Mo/Pt_(3)Ni NWs catalyst showed negligible structure degradation after 3,000 cycles(42 h)of durability test in 0.1 M HClO4 and 0.5 M ethanol,as compared to severe structural collapse and Ni dissolution for the pure Pt_(3)Ni NWs.The density functional theory(DFT)calculation also confirmed that both the surface and subsurface Mo atom could form Pt-Mo and Ni-Mo bonds with Pt and Ni,which were stronger than Pt-Ni bonds,to pin the Ni atoms in the unstable position and suppress the dissolution of surface Ni.The findings of this study indicate a promising pathway for the design and engineering of durable alloy nanocatalysts for direct ethanol fuel cell applications.展开更多
Strengthening the oxide-metal interfacial synergistic interaction in nanocatalysts is identified as potential strategy to boost intrinsic activities and the availability of active sites by regulating the surface/inter...Strengthening the oxide-metal interfacial synergistic interaction in nanocatalysts is identified as potential strategy to boost intrinsic activities and the availability of active sites by regulating the surface/interface environment of catalysts.Herein,the SnO_(2)/PtNi concave nanocubes(CNCs)enclosed by high-index facets(HIFs)with tunable SnO_(2)composition are successfully fabricated through combining the hydrothermal and self-assembly method.The interfacial interaction between ultrafine SnO_(2)nanoparticles and PtNi with HIFs surface structure is characterized by analytical techniques.The as-prepared 0.20%SnO_(2)/PtNi catalyst exhibits extraordinarily high catalytic performance for ethylene glycol electrooxidation(EGOR)in acidic conditions with specific activity of 3.06 mA/cm^(2),which represents 6.2-fold enhancement compared with the state-of-the-art Pt/C catalyst.Additionally,the kinetic study demonstrates that the strong interfacial interaction between SnO_(2)and PtNi not only degrades the activation energy barrier during the process of EGOR but also enhances the CO-resistance ability and long-term stability.This study provides a novel perspective to construct highly efficient and stable electrocatalysts for energy conversions.展开更多
基金Project supported by the National Natural Science Foundation of China(21972063)the Natural Science Foundation of Jiangsu Province(BK20200012).
文摘Sulfation treatment has been widely used to promote the catalytic performance of ceria(CeO_(2))based catalysts for the selective catalytic reduction of NO by NH_(3)(NH_(3)-SCR of NO).Praseodymium oxide(PrO_(x)),another commonly used rare earth material with similar structural properties as CeO_(2),also shows satistactory redox properties due to the facile redox cycle of Pr^(3+)■Pr^(4+).In this work,gas phase sulfation treatment with varied duration was performed on PrO_(x) at 200℃,and the NH_(3)-SCR activity of sulfated PrO_(x) was evaluated.Based on the results of systematic characterizations(e.g.,N_(2)-physisorption,NH_(3) oxidation,NO oxidation,in situ diffuse Fourier transform infrared spectroscopy),it is revealed that the catalytic performance of sulfated PrO_(x)is highly dependent on the sulfation time(or the amount of sulfate species deposited on PrO_(x)),which has a significant impact on the competitive reaction between NH_(3) oxidation and NH_(3)-SCR of NO,thus determining the NH_(3)-SCR activity of PrO_(x).This work provides new insight into tuning the interaction between PrO_(x) surface and reactants(NO,NH_(3))via sulfation treatment,which cam guide the design and application of PrO_(x)based catalysts for NH_(3)-SCR of NO in the future.
基金financial supports from the National Natural Science Foundation of China (Nos.21976081,21773106)。
文摘CeO_(2)/TiO_(2)(denoted as Ce Ti) catalysts obtained by solid-phase impregnation behaved better in lowtemperature selective catalytic reduction of NO_(x)with NH_(3)(NH_(3)-SCR) than that by conventional wet impregnation.To explore the main factors for activity distinction,the texture property,CeO_(2)dispersion and structure changes of TiO_(2)were comprehensively analyzed.It was found that surface changes of TiO_(2)had a significant impact on the improved activity.From results of inductively coupled plasma atomic emission spectrometer (ICP-AES),diffuse reflectance UV-vis spectroscopy (UV-vis-DRS) and Raman,it was inferred that Ce ions were partially incorporated into TiO_(2)lattice,accompanied with the formation of defects and vacancies during solid-phase impregnation.Accordingly,Ce Ti catalysts from solid-phase impregnation exhibited superiority in adsorption and activation of reactants.Further result from monitoring the preparation process indicated that the evolved NO played an important role in promoting Ce doping through depriving oxygen atoms on TiO_(2)surface.The interaction between Ce and Ti was enhanced.The catalyst performed better in NH_(3)-SCR,especially at low temperature,which testified the solid-phase impregnation could be an effective method to modulate interface structure for designing efficient catalyst.
基金Financial support from the National Natural Science Foundation of China,China(Nos.21972062,21976081,21976111)。
文摘A simple strategy of Cu modification was proposed to broaden the operation temperature window for NbCe catalyst.The best catalyst Cu0.010/Nb1Ce3 presented over 90%NO conversion in a wide temperature range of 200-400℃and exhibited an excellent H_(2)O or/and SO_(2) resistance at 275℃.To understand the promotional mechanism of Cu modification,the correlation among the"activity-structure-property"were tried to establish systematically.Cu species highly dispersed on NbCe catalyst to serve as the active component.The strong interaction among Cu,Nb and Ce promoted the emergence of NbO4 and induced more Bronsted acid sites.And Cu modification obviously enhanced the redox behavior of the NbCe catalyst.Besides,EPR probed the Cu species exited in the form of monomeric and dimeric Cu^(2+),the isolated Cu^(2+)acted as catalytic active sites to promote the reaction:Cu^(2+)-NO_(3)^(-)+NO(g)→Cu^(2+)-NO_(2)^(-)+NO_(2)(g).Then the generated NO_(2) would accelerate the fast-SCR reaction process and thus facilitated the lowtemperature deNO_(x) efficiency.Moreover,surface nitrates became unstable and easy to decompose after Cu modification,thus providing additional adsorption and activation sites for NH3,and ensuring the improvement of catalytic activity at high temperature.Since the NH3-SCR reaction followed by E-R reaction pathway efficaciously over Cu_(0.010)/Nb_(1)Ce_(3) catalyst,the excellent H_(2)O and SO_(2) resistance was as expected.
基金Project supported by the Opening Foundation of Jiangsu Key Laboratory of Vehicle Emissions Control(OVEC041)Major Scientific and Technological Project of Bingtuan(2018AA002)。
文摘Active species loss owing to reactant stream washing is a general problem which industrial catalysts suffer from.In case of catalysts synthesized by co-precipitation method,which have active species unused in bulk phase,can be regenerated by a simple thermal treatment that leads to active species in bulk phase migration to surface of the deactivated catalysts.In this work,the influence of regeneration temperature was investigated by employing ammonium hydroxide washing to simulate reactant stream washing of CeCoxO2 catalysts for NO+CO reaction.It is found that the deactivated catalyst can be regenerated by simple thermal treatment and increasing calcination temperature could accelerate the Co species migration from the bulk phase to surface of catalysts.
基金Project supported by the National Natural Science Foundation of China (22272077,22276097,21976081)Major Scientific and Technological Project of Bingtuan (2018AA002)。
文摘In this study,a series of Mn-Ce/Al_(2)O_(3) catalysts was prepared by different methods of depositionprecipitation(MnCeAl-DP),impregnation(MnCeAl-IM) and citric acid(MnCeAl-CA),and the distinct effect of preparation methods on NO_(x) removal performance at low temperature was explored.Results show that MnCeAl-DP exhibits not only the best activity but also the highest resistance against SO_(2)/H_(2)O.With the assistance of comprehensive characterizations from scanning electron microscopy(SEM),Brunauer-Emmett-Teller(BET),X-ray diffraction(XRD),H_(2)-temperature programmed reduction(H_(2)-TPR),NH_(3)-te mperature programmed deso rption(NH_(3)-TPD),and X-ray photoelectron spectroscopy(XPS),it is revealed that the MnCeAl-DP sample owns admired features of large surface area and pore volume,enriched Mn^(4+) and chemisorbed oxygen species originating from enhanced interaction between MnO_x and CeO_(2),as well as improved adsorption capacity to NH_(3) and NO.All these factors contribute to activity enhancement.Further in-situ DRIFTS studies reveal that the improvement of NH_(3)-SCR performance over MnCeAI-DP is related to the formation of abundant nitrate species,which is beneficial to the "NH_(4)NO_(3)" reaction pathway and thus enhances low-temperature activity.
基金The authors acknowledge financial support from the National Natural Science Foundation of China(NSFC)(No.21573286)the Key Scientific and Technological Innovation projects in Shandong Province(No.2019JZZY010343)the open fund of Jiangsu Key Laboratory of Vehicle Emissions Control,Nanjing University.
文摘Pt_(3)Ni alloy structure is an effective strategy to accelerate ethanol oxidation reaction(EOR),while the stability in acid electrolyte is the fatal weakness and the current density still needs to be enhanced.Herein,ultralong Pt_(3)Ni nanowires tailored by trace Mo(Mo/Pt_(3)Ni NWs)were successfully synthesized by surfactant free method.The specific activity of the optimized catalyst was 2.66 mA·cm^(-2),which is approximately 2.16 and 4.6-fold that of Pt_(3)Ni NWs and commercial Pt/C catalyst,respectively.Most importantly,the Mo/Pt_(3)Ni NWs catalyst showed negligible structure degradation after 3,000 cycles(42 h)of durability test in 0.1 M HClO4 and 0.5 M ethanol,as compared to severe structural collapse and Ni dissolution for the pure Pt_(3)Ni NWs.The density functional theory(DFT)calculation also confirmed that both the surface and subsurface Mo atom could form Pt-Mo and Ni-Mo bonds with Pt and Ni,which were stronger than Pt-Ni bonds,to pin the Ni atoms in the unstable position and suppress the dissolution of surface Ni.The findings of this study indicate a promising pathway for the design and engineering of durable alloy nanocatalysts for direct ethanol fuel cell applications.
基金the National Natural Science Foundation of China(No.21573286)the Key Scientific and Technological Innovation Project in Shandong Province(No.2019JZZY010343).
文摘Strengthening the oxide-metal interfacial synergistic interaction in nanocatalysts is identified as potential strategy to boost intrinsic activities and the availability of active sites by regulating the surface/interface environment of catalysts.Herein,the SnO_(2)/PtNi concave nanocubes(CNCs)enclosed by high-index facets(HIFs)with tunable SnO_(2)composition are successfully fabricated through combining the hydrothermal and self-assembly method.The interfacial interaction between ultrafine SnO_(2)nanoparticles and PtNi with HIFs surface structure is characterized by analytical techniques.The as-prepared 0.20%SnO_(2)/PtNi catalyst exhibits extraordinarily high catalytic performance for ethylene glycol electrooxidation(EGOR)in acidic conditions with specific activity of 3.06 mA/cm^(2),which represents 6.2-fold enhancement compared with the state-of-the-art Pt/C catalyst.Additionally,the kinetic study demonstrates that the strong interfacial interaction between SnO_(2)and PtNi not only degrades the activation energy barrier during the process of EGOR but also enhances the CO-resistance ability and long-term stability.This study provides a novel perspective to construct highly efficient and stable electrocatalysts for energy conversions.
