A series of perovskite type oxides and supported Ag catalysts were prepared, and characterized by X ray diffraction (XRD) and X ray photoelectron spectroscopy (XPS). The catalytic activities of the catalyst...A series of perovskite type oxides and supported Ag catalysts were prepared, and characterized by X ray diffraction (XRD) and X ray photoelectron spectroscopy (XPS). The catalytic activities of the catalysts as well as influencing factors on catalytic activity have been investigated for the simultaneous removal of NOx and diesel soot particulate. An increase in catalytic activity for the selective reduction of NOx was observed with Ag addition in these perovskite oxides, especially with 5% Ag loading. This catalyst could be a promising candidate of catalytic material for the simultaneous elimination of NOx and diesel soot.展开更多
Ag‐Cu‐Cl/BaCO3 catalysts with different Cl and Cu loadings, prepared by the reduction deposition impregnation method, were investigated for gas‐phase epoxidation of propylene by molecular oxygen and characterized b...Ag‐Cu‐Cl/BaCO3 catalysts with different Cl and Cu loadings, prepared by the reduction deposition impregnation method, were investigated for gas‐phase epoxidation of propylene by molecular oxygen and characterized by X‐ray diffraction, X‐ray photoelectron spectroscopy and O2 temperatureprogrammed desorption. Ag‐Cu‐Cl/BaCO3 catalyst with 0.036 wt% Cu and 0.060 wt% Cl exhibitedthe highest catalytic performance for gas‐phase epoxidation of propylene by molecular oxygen. Apropylene oxide selectivity of 83.7% and propylene conversion of 1.2% were achieved under thereaction conditions of 20% C3H6‐10% O2‐70% N2, 200 °C, 0.1 MPa and 3000 h?1. Increasing the Clloading allowed Ag to ensemble easier, whereas changing the Cu loading showed little effect on Agcrystallite size. The appropriate Cl loading of Ag‐Cu‐Cl/BaCO3 catalyst can reduce the dissociationadsorption of oxygen to atomic oxygen species leading to the combustion of propylene to CO2, whichbenefits epoxidation of propylene by molecular oxygen. Excessive Cl loading of Ag‐Cu‐Cl/BaCO3catalyst decreases propylene conversion and propylene oxide selectivity remarkably because of Clpoisoning. The appropriate Cu loading of Ag‐Cu‐Cl/BaCO3 catalyst is efficient for the epoxidation ofpropylene by molecular oxygen, and an excess Cu loading decreases propylene oxide selectivitybecause the aggregation of Cu species increases the exposed surfaces of Ag nanoparticles, whichwas shown by slight increases in atomic oxygen species adsorbed. The appropriate loadings of Cu and Cl of Ag‐Cu‐Cl/BaCO3 catalyst are important to strike the balance between molecular oxygen and atomic oxygen species to create a favorable epoxidation of propylene by molecular oxygen.展开更多
In this study,Ag/γ-Al_(2)O_(3)catalysts were synthesized by an Ar dielectric barrier discharge plasma using silver nitrate as the Ag source andγ-alumina(γ-Al_(2)O_(3))as the support.It is revealed that plasma can r...In this study,Ag/γ-Al_(2)O_(3)catalysts were synthesized by an Ar dielectric barrier discharge plasma using silver nitrate as the Ag source andγ-alumina(γ-Al_(2)O_(3))as the support.It is revealed that plasma can reduce silver ions to generate crystalline silver nanoparticles(Ag NPs)of good dispersion and uniformity on the alumina surface,leading to the formation of Ag/γ-Al_(2)O_(3)catalysts in a green manner without traditional chemical reductants.Ag/γ-Al_(2)O_(3)exhibited good catalytic activity and stability in CO oxidation reactions,and the activity increased with increase in the Ag content.For catalysts with more than 2 wt%Ag,100%CO conversion can be achieved at 300°C.The catalytic activity of the Ag/γ-Al_(2)O_(3)catalysts is also closely related to the size of theγ-alumina,where Ag/nano-γ-Al_(2)O_(3)catalysts demonstrate better performance than Ag/micro-γ-Al_(2)O_(3)catalysts with the same Ag content.In addition,the catalytic properties of plasma-generated Ag/nano-γ-Al_(2)O_(3)(Ag/γ-Al_(2)O_(3)-P)catalysts were compared with those of Ag/nano-γ-Al_(2)O_(3)catalysts prepared by the traditional calcination approach(Ag/γ-Al_(2)O_(3)-C),with the plasma-generated samples demonstrating better overall performance.This simple,rapid and green plasma process is considered to be applicable for the synthesis of diverse noble metal-based catalysts.展开更多
Our recent theoretical studies have screened out CuCs-doped Ag-based promising catalysts for ethylene epoxidation[ACS Catal.11,3371(2021)].The theoretical results were based on surface modeling,while in the actual rea...Our recent theoretical studies have screened out CuCs-doped Ag-based promising catalysts for ethylene epoxidation[ACS Catal.11,3371(2021)].The theoretical results were based on surface modeling,while in the actual reaction process Ag catalysts are particle shaped.In this work,we combine density functional theory(DFT),Wulff construction theory,and micro kinetic analysis to study the catalytic performance of Ag catalysts at the particle model.It demonstrates that the CuCs-doped Ag catalysts are superior to pure Ag catalysts in terms of selectivity and activity,which is further proved by experimental validation.The characterization analysis finds that both Cu and Cs dopant promote particle growth as well as particle dispersion,resulting in a grain boundary-rich Ag particle.Besides,CuCs also facilitate electrophilic atomic oxygen formation on catalyst surface,which is benefitial for ethylene oxide formation and desorption.Our work provides a case study for catalyst design by combining theory and experiment.展开更多
Activated carbon （AC） supported silver catalysts were prepared by incipient wetness impregnation method and their catalytic performance for CO preferential oxidation （PROX） in excess H2 was evaluated. Ag/AC cataly...Activated carbon （AC） supported silver catalysts were prepared by incipient wetness impregnation method and their catalytic performance for CO preferential oxidation （PROX） in excess H2 was evaluated. Ag/AC catalysts, after reduction in H2 at low temperatures （≤200 ℃） following heat treatment in He at 200 ℃ （He200H200）, exhibited the best catalytic properties. Temperature-programmed desorption （TPD）, X-ray diffraction （XRD） and temperature-programmed reduction （TPR） results indicated that silver oxides were produced during heat treatment in He at 200 ℃ which were reduced to metal silver nanoparticles in H2 at low temperatures （≤200 ℃）, simultaneously generating the adsorbed water/OH. CO conversion was enhanced 40% after water treatment following heat treatment in He at 600 ℃. These results imply that the metal silver nanoparticles are the active species and the adsorbed water/OH has noticeable promotion effects on CO oxidation. However, the promotion effect is still limited compared to gold catalysts under the similar conditions, which may be the reason of low selectivity to CO oxidation in PROX over silver catalysts. The reported Ag/AC-S-He catalyst after He200H200 treatment displayed similar PROX of CO reaction properties to Ag/SiO2. This means that Ag/AC catalyst is also an efficient low-temperature CO oxidation catalyst.展开更多
Fully formulated lean NOx trap(LNT)catalysts of the type Pt/Rh/BaO/Al2O3 were prepared with and without incorporation of CeO2-ZrO2 in the washcoat,and their NOx reduction behavior was evaluated in steady-state,continu...Fully formulated lean NOx trap(LNT)catalysts of the type Pt/Rh/BaO/Al2O3 were prepared with and without incorporation of CeO2-ZrO2 in the washcoat,and their NOx reduction behavior was evaluated in steady-state,continuous flow experiments.In the fresh state, the CeO2-ZrO2 addition was found to exert little effect on NOx reduction activity using H2,CO,and NH3 as the reductants.However,after simulated road aging,NOx reduction activity was significantly impaired for the CeO2-ZrO2-free catalyst,whereas the performance of the CeO2-ZrO2-containing analog was affected to only a minor degree.These differences are explained on the basis of high-resolution transmission electron microscopy measurements showing that Pt supported on CeO2-ZrO2 remained highly dispersed after aging,whereas Pt supported on BaO/Al2O3 underwent significant sintering.In addition,the Pt/CeO2-ZrO2 component did not accumulate sulfur during aging, unlike Pt/BaO/Al2O3 for which significant sulfation of the Ba phase occurred.For both catalysts,selectivity to NH3 in NO and NO2 reduction by H2 increased after the catalyst aging,indicative of a change in the relative surface coverages of N and H ad-atoms on the precious metal sites.展开更多
Silver(9 wt.%)was loaded on Co_(3)O_(4)-nanofiber using reduction and impregnation methods,respectively.Due to the stronger electronegativity of silver,the ratios of surface Co^(3+)/Co^(2+) on Ag/Co_(3)O_(4) were high...Silver(9 wt.%)was loaded on Co_(3)O_(4)-nanofiber using reduction and impregnation methods,respectively.Due to the stronger electronegativity of silver,the ratios of surface Co^(3+)/Co^(2+) on Ag/Co_(3)O_(4) were higher than on Co_(3)O_(4),which further led to more adsorbed oxygen species as a result of the charge compensation.Moreover,the introducing of silver also obviously improved the reducibility of Co_(3)O_(4).Hence the Ag/Co_(3)O_(4) showed better catalytic performance than Co_(3)O_(4) in benzene oxidation.Compared with the Ag/Co_(3)O_(4) synthesized via impregnation method,the one prepared using reduction method(named as Ag Co-R)exhibited higher contents of surface Co^(3+) and adsorbed oxygen species,stronger reducibility,as well as more active surface lattice oxygen species.Consequently,Ag Co-R showed lowest T_(90) value of 183℃,admirable catalytic stability,largest normalized reaction rate of1.36×10^(-4)mol/(h·m^(2))(150℃),and lowest apparent activation energy(E_(a))of 63.2 kJ/mol.The analyzing of in-situ DRIFTS indicated benzene molecules were successively oxidized to phenol,o-benzoquinone,small molecular intermediates,and finally to CO_(2) and water on the surface of Ag Co-R.At last,potential reaction pathways including five detailed steps were proposed.展开更多
The side-glowing optical fibers (SOFs) were chosen as the conducting medium of endogenous light; and 20 mg·L-1 methylene blue was chosen as the target to be degraded. The SOF is made up of quartz core with a sili...The side-glowing optical fibers (SOFs) were chosen as the conducting medium of endogenous light; and 20 mg·L-1 methylene blue was chosen as the target to be degraded. The SOF is made up of quartz core with a silicon cladding, which can emit light through side surface more uniformly and transmit light for longer distance to avoid attenuation of light by liquid medium. The filament lamp was chosen as visible light source. Different reaction conditions, such as the presence of optical fiber or not, the quantity of SOF, light irradiation intensity were tested by measuring the methylene blue degradation of methylene blue. The results show that suitable reaction conditions were 1.167 g·L-1 Ag + /TiO 2 with 7% (by mass) of Ag + doped in TiO 2 , and 500 roots of SOF (30 cm length in solution). The photocatalytic degradation efficiency under 300W lamp irradiation for 8h was about 97%. And the photocatalytic degradation efficiency of methylene blue degradation was proportional to SOF quantity, light irradiation intensity and catalytic dosage within a certain range. Compared with general UV and visible light SOFs could save a huge amount of energy and cost, in the potential applications in dealing with organic pollutants on a large scale.展开更多
The melting behaviour of four typical core-shell structured 309-atom Ag-Rh bimetallic clusters, with decahedral and icosahedral geometric configurations, is investigated by using molecular dynamics simulation, based o...The melting behaviour of four typical core-shell structured 309-atom Ag-Rh bimetallic clusters, with decahedral and icosahedral geometric configurations, is investigated by using molecular dynamics simulation, based on the Sutton-Chen potential. The initial atomic configurations are obtained from semi-grand canonical ensemble Monte Carlo simulations. It is found that the melting point temperature Tm increases with the mole fraction of Rh in the bimetallic clusters, and Tm of Ag-Rh icosahedral clusters is higher than those of Ag-Rh decahedral clusters with the same Rh mole fraction. It is also found that the Ag atoms lie on the surface of Ag-Rh bimetallic clusters even after melting.展开更多
Electrochemical CO_(2)reduction to C_(2)H_(4)can provide a sustainable route to reduce globally accelerating CO_(2)emissions and produce energy-rich chemical feedstocks.However,the poor selectivity in C_(2)H_(4)electr...Electrochemical CO_(2)reduction to C_(2)H_(4)can provide a sustainable route to reduce globally accelerating CO_(2)emissions and produce energy-rich chemical feedstocks.However,the poor selectivity in C_(2)H_(4)electrosynthesis limits its implementation in industrially interesting processes.Herein,we report a composite structured catalyst composed of Ag and Cu_(2)O with different crystal faces to achieve highly efficient reduction of CO_(2)to C_(2)H_(4).The catalyst composed of Ag and octahedral Cu_(2)O enclosed with(111)facet exhibits the best CO_(2)electroreduction performance,with the Faradaic efficiency(FE)and partial current density reaching 66.8%and 17.8 mA cm2 for C_(2)H_(4)product at-1.2 VRHE in 0.5 M KHCO_(3),respectively.Physical characterization and electrochemical test analysis indicate that the high selectivity for C_(2)H_(4)product stems from the synergistic effect of crystal faces control engineering and tandem catalysis.Specifically,Ag can provide optimal availability of CO intermediate by suppressing hydrogen evolution;subsequently,C-C coupling is promoted on the intimate surface of Cu_(2)O with facetdependent selectivity.The insights gained from this work may be beneficial for designing efficient multicomponent catalysts for improving the selectivity of electrochemical CO_(2)reduction reaction to generate C2þproducts.展开更多
The electrochemical conversion of CO_(2) to C_(2+)products represents a significant technological opportunity for addressing global climate change.Nevertheless,copper-based catalysts continue to present challenges in ...The electrochemical conversion of CO_(2) to C_(2+)products represents a significant technological opportunity for addressing global climate change.Nevertheless,copper-based catalysts continue to present challenges in terms of selectivity and the long-term stability of C_(2+)products.In this study,we demonstrate that the introduction of a second metal,silver(Ag),onto copper-based catalysts represents an effective strategy for enhancing the selectivity and reactivity of these catalysts in the electrochemical CO_(2) reduction reaction.This approach involves modulating the adsorption strength or geometry of CO intermediates on the Cu-based catalyst surface.The results demonstrate that the Faradaic efficiency(FE)of C_(2+)products in the electrochemical CO_(2) reduction reaction over a 5%Ag/Cu catalyst is 77%-80% within the current density range of 800 to 1000 mA·cm^(-2).Furthermore,stability tests were conducted on the electrochemical CO_(2) reduction reaction in a membrane electrolyzer using pure water as the electrolyte.Following a 15 h testing period at a current of -1000 mA,the FE of CO_(2) reduction was observed to be 45%,indicating favorable stability.This provides a foundation for further research and development in the industrial application of electrochemical CO_(2) reduction.展开更多
Reconstruction of supported nanocatalysts often occurs in gas-solid reactions and significantly affects the catalytic performance,yet it is much less explored in liquid-phase environment.Herein,we find that highly-dis...Reconstruction of supported nanocatalysts often occurs in gas-solid reactions and significantly affects the catalytic performance,yet it is much less explored in liquid-phase environment.Herein,we find that highly-dispersed Ag nanocatalysts,i.e.,AgOx clusters,supported on alumina,silica,and titania,can aggregate into larger Ag or Ag2O particles after immersing in liquid-phase media at room temperature.The spontaneous aggregation of AgOx clusters in liquid water is attributed to liquid-phase Ostwald ripening through dissolution of AgOx clusters into water and subsequent redeposition to form Ag2O particles.The immersion into organic solvents such as ethanol leads to reduction of AgOx clusters and further growth into Ag particles.This work reveals that liquid-phase reaction media can induce substantial structural evolution of supported nanostructured catalysts,which should be carefully considered in liquid-solid interface catalytic reactions such as electrocatalysis,environmental catalysis,and organic synthesis in liquid phase.展开更多
The electrochemical reduction of NH4HCO3 to syngas can bypass the high energy consumption of high-purity CO_(2)release and compression after the ammonia-based CO_(2)capture process.This technology has broad prospects ...The electrochemical reduction of NH4HCO3 to syngas can bypass the high energy consumption of high-purity CO_(2)release and compression after the ammonia-based CO_(2)capture process.This technology has broad prospects in industrial applications and carbon neutrality.A zeolitic imidazolate framework-8 precursor was introduced with different Ag contents via colloid chemical synthesis.This material was carbonized at 1000℃to obtain AgZn zeolitic imidazolate framework derived nitrogen carbon catalysts,which were used for the first time for boosting the direct conversion of NH4HCO3 electrolyte to syngas.The AgZn zeolitic imidazolate framework derived nitrogen carbon catalyst with a Ag/Zn ratio of 0.5:1 achieved the highest CO Faradaic efficiency of 52.0%with a current density of 1.15 mA·cm^(−2)at−0.5 V,a H2/CO ratio of 1-2(−0.5 to−0.7 V),and a stable catalytic activity of more than 6 h.Its activity is comparable to that of the CO_(2)-saturated NH4HCO3 electrolyte.The highly discrete Ag-N_(x)and Zn-N_(x)nodes may have combined catalytic effects in the catalysts synthesized by appropriate Ag doping and sufficient carbonization.These nodes could increase active sites of catalysts,which is conducive to the transport and adsorption of reactant CO_(2)and the stability of*COOH intermediate,thus can improve the selectivity and catalytic activity of CO.展开更多
文摘A series of perovskite type oxides and supported Ag catalysts were prepared, and characterized by X ray diffraction (XRD) and X ray photoelectron spectroscopy (XPS). The catalytic activities of the catalysts as well as influencing factors on catalytic activity have been investigated for the simultaneous removal of NOx and diesel soot particulate. An increase in catalytic activity for the selective reduction of NOx was observed with Ag addition in these perovskite oxides, especially with 5% Ag loading. This catalyst could be a promising candidate of catalytic material for the simultaneous elimination of NOx and diesel soot.
基金supported by National Basic Research Program of China (2013CB933200)Commission of Science and Technology of Shanghai Municipality (15DZ1205305)~~
文摘Ag‐Cu‐Cl/BaCO3 catalysts with different Cl and Cu loadings, prepared by the reduction deposition impregnation method, were investigated for gas‐phase epoxidation of propylene by molecular oxygen and characterized by X‐ray diffraction, X‐ray photoelectron spectroscopy and O2 temperatureprogrammed desorption. Ag‐Cu‐Cl/BaCO3 catalyst with 0.036 wt% Cu and 0.060 wt% Cl exhibitedthe highest catalytic performance for gas‐phase epoxidation of propylene by molecular oxygen. Apropylene oxide selectivity of 83.7% and propylene conversion of 1.2% were achieved under thereaction conditions of 20% C3H6‐10% O2‐70% N2, 200 °C, 0.1 MPa and 3000 h?1. Increasing the Clloading allowed Ag to ensemble easier, whereas changing the Cu loading showed little effect on Agcrystallite size. The appropriate Cl loading of Ag‐Cu‐Cl/BaCO3 catalyst can reduce the dissociationadsorption of oxygen to atomic oxygen species leading to the combustion of propylene to CO2, whichbenefits epoxidation of propylene by molecular oxygen. Excessive Cl loading of Ag‐Cu‐Cl/BaCO3catalyst decreases propylene conversion and propylene oxide selectivity remarkably because of Clpoisoning. The appropriate Cu loading of Ag‐Cu‐Cl/BaCO3 catalyst is efficient for the epoxidation ofpropylene by molecular oxygen, and an excess Cu loading decreases propylene oxide selectivitybecause the aggregation of Cu species increases the exposed surfaces of Ag nanoparticles, whichwas shown by slight increases in atomic oxygen species adsorbed. The appropriate loadings of Cu and Cl of Ag‐Cu‐Cl/BaCO3 catalyst are important to strike the balance between molecular oxygen and atomic oxygen species to create a favorable epoxidation of propylene by molecular oxygen.
基金financial support from National Natural Science Foundation of China(Nos.52004102 and 22078125)Postdoctoral Science Foundation of China(No.2021M690068)+2 种基金Fundamental Research Funds for the Central Universities(Nos.JUSRP221018 and JUSRP622038)Key Laboratory of Green Cleaning Technology and Detergent of Zhejiang Province(No.Q202204)Open Project of Key Laboratory of Green Chemical Engineering Process of Ministry of Education(No.GCP202112)。
文摘In this study,Ag/γ-Al_(2)O_(3)catalysts were synthesized by an Ar dielectric barrier discharge plasma using silver nitrate as the Ag source andγ-alumina(γ-Al_(2)O_(3))as the support.It is revealed that plasma can reduce silver ions to generate crystalline silver nanoparticles(Ag NPs)of good dispersion and uniformity on the alumina surface,leading to the formation of Ag/γ-Al_(2)O_(3)catalysts in a green manner without traditional chemical reductants.Ag/γ-Al_(2)O_(3)exhibited good catalytic activity and stability in CO oxidation reactions,and the activity increased with increase in the Ag content.For catalysts with more than 2 wt%Ag,100%CO conversion can be achieved at 300°C.The catalytic activity of the Ag/γ-Al_(2)O_(3)catalysts is also closely related to the size of theγ-alumina,where Ag/nano-γ-Al_(2)O_(3)catalysts demonstrate better performance than Ag/micro-γ-Al_(2)O_(3)catalysts with the same Ag content.In addition,the catalytic properties of plasma-generated Ag/nano-γ-Al_(2)O_(3)(Ag/γ-Al_(2)O_(3)-P)catalysts were compared with those of Ag/nano-γ-Al_(2)O_(3)catalysts prepared by the traditional calcination approach(Ag/γ-Al_(2)O_(3)-C),with the plasma-generated samples demonstrating better overall performance.This simple,rapid and green plasma process is considered to be applicable for the synthesis of diverse noble metal-based catalysts.
基金This work is supported by PetroChina Innovation Foundation(2019D-5007-0403).
文摘Our recent theoretical studies have screened out CuCs-doped Ag-based promising catalysts for ethylene epoxidation[ACS Catal.11,3371(2021)].The theoretical results were based on surface modeling,while in the actual reaction process Ag catalysts are particle shaped.In this work,we combine density functional theory(DFT),Wulff construction theory,and micro kinetic analysis to study the catalytic performance of Ag catalysts at the particle model.It demonstrates that the CuCs-doped Ag catalysts are superior to pure Ag catalysts in terms of selectivity and activity,which is further proved by experimental validation.The characterization analysis finds that both Cu and Cs dopant promote particle growth as well as particle dispersion,resulting in a grain boundary-rich Ag particle.Besides,CuCs also facilitate electrophilic atomic oxygen formation on catalyst surface,which is benefitial for ethylene oxide formation and desorption.Our work provides a case study for catalyst design by combining theory and experiment.
基金supported by the National Natural Science Foundation of China (No. 21207039)the Natural Science Foundation of Guangdong Province, China (Grant No. S2011010000737)+2 种基金the Doctoral Fund of Ministry of Education of China (20110172120017)the Fundamental Research Funds for the Central Universities (Grant No. 2011zm 0048)the Key Laboratory of Renewable Energy and Gas Hydrate, Chinese Academy of Sciences (No. Y007K1)
文摘Activated carbon （AC） supported silver catalysts were prepared by incipient wetness impregnation method and their catalytic performance for CO preferential oxidation （PROX） in excess H2 was evaluated. Ag/AC catalysts, after reduction in H2 at low temperatures （≤200 ℃） following heat treatment in He at 200 ℃ （He200H200）, exhibited the best catalytic properties. Temperature-programmed desorption （TPD）, X-ray diffraction （XRD） and temperature-programmed reduction （TPR） results indicated that silver oxides were produced during heat treatment in He at 200 ℃ which were reduced to metal silver nanoparticles in H2 at low temperatures （≤200 ℃）, simultaneously generating the adsorbed water/OH. CO conversion was enhanced 40% after water treatment following heat treatment in He at 600 ℃. These results imply that the metal silver nanoparticles are the active species and the adsorbed water/OH has noticeable promotion effects on CO oxidation. However, the promotion effect is still limited compared to gold catalysts under the similar conditions, which may be the reason of low selectivity to CO oxidation in PROX over silver catalysts. The reported Ag/AC-S-He catalyst after He200H200 treatment displayed similar PROX of CO reaction properties to Ag/SiO2. This means that Ag/AC catalyst is also an efficient low-temperature CO oxidation catalyst.
基金supported by the U.S.Department of Energy(DOE)under award No.DE-EE0000205
文摘Fully formulated lean NOx trap(LNT)catalysts of the type Pt/Rh/BaO/Al2O3 were prepared with and without incorporation of CeO2-ZrO2 in the washcoat,and their NOx reduction behavior was evaluated in steady-state,continuous flow experiments.In the fresh state, the CeO2-ZrO2 addition was found to exert little effect on NOx reduction activity using H2,CO,and NH3 as the reductants.However,after simulated road aging,NOx reduction activity was significantly impaired for the CeO2-ZrO2-free catalyst,whereas the performance of the CeO2-ZrO2-containing analog was affected to only a minor degree.These differences are explained on the basis of high-resolution transmission electron microscopy measurements showing that Pt supported on CeO2-ZrO2 remained highly dispersed after aging,whereas Pt supported on BaO/Al2O3 underwent significant sintering.In addition,the Pt/CeO2-ZrO2 component did not accumulate sulfur during aging, unlike Pt/BaO/Al2O3 for which significant sulfation of the Ba phase occurred.For both catalysts,selectivity to NH3 in NO and NO2 reduction by H2 increased after the catalyst aging,indicative of a change in the relative surface coverages of N and H ad-atoms on the precious metal sites.
基金supported by the National Natural Science Foundation of China(No.22176123)the Natural Science Foundation of Xinjiang(Nos.2020D01C021,2021D01C036)the National Natural Science Foundation of China-Xinjiang Joint Fund(No.U2003123)。
文摘Silver(9 wt.%)was loaded on Co_(3)O_(4)-nanofiber using reduction and impregnation methods,respectively.Due to the stronger electronegativity of silver,the ratios of surface Co^(3+)/Co^(2+) on Ag/Co_(3)O_(4) were higher than on Co_(3)O_(4),which further led to more adsorbed oxygen species as a result of the charge compensation.Moreover,the introducing of silver also obviously improved the reducibility of Co_(3)O_(4).Hence the Ag/Co_(3)O_(4) showed better catalytic performance than Co_(3)O_(4) in benzene oxidation.Compared with the Ag/Co_(3)O_(4) synthesized via impregnation method,the one prepared using reduction method(named as Ag Co-R)exhibited higher contents of surface Co^(3+) and adsorbed oxygen species,stronger reducibility,as well as more active surface lattice oxygen species.Consequently,Ag Co-R showed lowest T_(90) value of 183℃,admirable catalytic stability,largest normalized reaction rate of1.36×10^(-4)mol/(h·m^(2))(150℃),and lowest apparent activation energy(E_(a))of 63.2 kJ/mol.The analyzing of in-situ DRIFTS indicated benzene molecules were successively oxidized to phenol,o-benzoquinone,small molecular intermediates,and finally to CO_(2) and water on the surface of Ag Co-R.At last,potential reaction pathways including five detailed steps were proposed.
文摘The side-glowing optical fibers (SOFs) were chosen as the conducting medium of endogenous light; and 20 mg·L-1 methylene blue was chosen as the target to be degraded. The SOF is made up of quartz core with a silicon cladding, which can emit light through side surface more uniformly and transmit light for longer distance to avoid attenuation of light by liquid medium. The filament lamp was chosen as visible light source. Different reaction conditions, such as the presence of optical fiber or not, the quantity of SOF, light irradiation intensity were tested by measuring the methylene blue degradation of methylene blue. The results show that suitable reaction conditions were 1.167 g·L-1 Ag + /TiO 2 with 7% (by mass) of Ag + doped in TiO 2 , and 500 roots of SOF (30 cm length in solution). The photocatalytic degradation efficiency under 300W lamp irradiation for 8h was about 97%. And the photocatalytic degradation efficiency of methylene blue degradation was proportional to SOF quantity, light irradiation intensity and catalytic dosage within a certain range. Compared with general UV and visible light SOFs could save a huge amount of energy and cost, in the potential applications in dealing with organic pollutants on a large scale.
基金Supported by the National Natural Science Foundation of China under Nos 20236010 and 20476004, and the National Basic Research Programme of China under Grant No G2003CB615807.
文摘The melting behaviour of four typical core-shell structured 309-atom Ag-Rh bimetallic clusters, with decahedral and icosahedral geometric configurations, is investigated by using molecular dynamics simulation, based on the Sutton-Chen potential. The initial atomic configurations are obtained from semi-grand canonical ensemble Monte Carlo simulations. It is found that the melting point temperature Tm increases with the mole fraction of Rh in the bimetallic clusters, and Tm of Ag-Rh icosahedral clusters is higher than those of Ag-Rh decahedral clusters with the same Rh mole fraction. It is also found that the Ag atoms lie on the surface of Ag-Rh bimetallic clusters even after melting.
基金This work was supported by the University of Science and Technology Beijing.DG acknowledges the financial support from 111 Project(no.B170003)Foshan Science and Technology Innovation Project(no.2018IT100363).
文摘Electrochemical CO_(2)reduction to C_(2)H_(4)can provide a sustainable route to reduce globally accelerating CO_(2)emissions and produce energy-rich chemical feedstocks.However,the poor selectivity in C_(2)H_(4)electrosynthesis limits its implementation in industrially interesting processes.Herein,we report a composite structured catalyst composed of Ag and Cu_(2)O with different crystal faces to achieve highly efficient reduction of CO_(2)to C_(2)H_(4).The catalyst composed of Ag and octahedral Cu_(2)O enclosed with(111)facet exhibits the best CO_(2)electroreduction performance,with the Faradaic efficiency(FE)and partial current density reaching 66.8%and 17.8 mA cm2 for C_(2)H_(4)product at-1.2 VRHE in 0.5 M KHCO_(3),respectively.Physical characterization and electrochemical test analysis indicate that the high selectivity for C_(2)H_(4)product stems from the synergistic effect of crystal faces control engineering and tandem catalysis.Specifically,Ag can provide optimal availability of CO intermediate by suppressing hydrogen evolution;subsequently,C-C coupling is promoted on the intimate surface of Cu_(2)O with facetdependent selectivity.The insights gained from this work may be beneficial for designing efficient multicomponent catalysts for improving the selectivity of electrochemical CO_(2)reduction reaction to generate C2þproducts.
基金financially supported in part by National Energy R&D Center of Petroleum Technology(RIPP,SINOPEC)the National Key R&D Program of China(No.2021YFA1501502)+4 种基金the National Natural Science Foundation of China(Nos.52261135635,22232003,U23A2091,and 22479139)Anhui Provincial Natural Science Foundation(No.2408085JX001)Youth Innovation Promotion Association of CAS(No.Y2023129)Fundamental Research Funds for the Central Universities(Nos.WK2060000099 and KY2140000031)West Light Foundation of Chinese Academy of Sciences(No.xbzg-zdsys-202209).
文摘The electrochemical conversion of CO_(2) to C_(2+)products represents a significant technological opportunity for addressing global climate change.Nevertheless,copper-based catalysts continue to present challenges in terms of selectivity and the long-term stability of C_(2+)products.In this study,we demonstrate that the introduction of a second metal,silver(Ag),onto copper-based catalysts represents an effective strategy for enhancing the selectivity and reactivity of these catalysts in the electrochemical CO_(2) reduction reaction.This approach involves modulating the adsorption strength or geometry of CO intermediates on the Cu-based catalyst surface.The results demonstrate that the Faradaic efficiency(FE)of C_(2+)products in the electrochemical CO_(2) reduction reaction over a 5%Ag/Cu catalyst is 77%-80% within the current density range of 800 to 1000 mA·cm^(-2).Furthermore,stability tests were conducted on the electrochemical CO_(2) reduction reaction in a membrane electrolyzer using pure water as the electrolyte.Following a 15 h testing period at a current of -1000 mA,the FE of CO_(2) reduction was observed to be 45%,indicating favorable stability.This provides a foundation for further research and development in the industrial application of electrochemical CO_(2) reduction.
基金National Key Research and Development Program of China(Nos.2021YFA1502800,2022YFA1504800,and 2022YFA1504500)the National Natural Science Foundation of China(Nos.21825203,22288201,22332006,and 22321002)+2 种基金Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB0600300)the Fundamental Research Funds for the Central Universities(No.20720220009)Photon Science Center for Carbon Neutrality。
文摘Reconstruction of supported nanocatalysts often occurs in gas-solid reactions and significantly affects the catalytic performance,yet it is much less explored in liquid-phase environment.Herein,we find that highly-dispersed Ag nanocatalysts,i.e.,AgOx clusters,supported on alumina,silica,and titania,can aggregate into larger Ag or Ag2O particles after immersing in liquid-phase media at room temperature.The spontaneous aggregation of AgOx clusters in liquid water is attributed to liquid-phase Ostwald ripening through dissolution of AgOx clusters into water and subsequent redeposition to form Ag2O particles.The immersion into organic solvents such as ethanol leads to reduction of AgOx clusters and further growth into Ag particles.This work reveals that liquid-phase reaction media can induce substantial structural evolution of supported nanostructured catalysts,which should be carefully considered in liquid-solid interface catalytic reactions such as electrocatalysis,environmental catalysis,and organic synthesis in liquid phase.
基金This work was supported by the 2022 Heilongjiang Province’s“Emission and carbon neutrality”the open competition mechanism to select the best candidate project(Adsorption-type compression of carbon dioxide energy storage key technology research and demonstration:Grant No.2022ZXJ09C01).
文摘The electrochemical reduction of NH4HCO3 to syngas can bypass the high energy consumption of high-purity CO_(2)release and compression after the ammonia-based CO_(2)capture process.This technology has broad prospects in industrial applications and carbon neutrality.A zeolitic imidazolate framework-8 precursor was introduced with different Ag contents via colloid chemical synthesis.This material was carbonized at 1000℃to obtain AgZn zeolitic imidazolate framework derived nitrogen carbon catalysts,which were used for the first time for boosting the direct conversion of NH4HCO3 electrolyte to syngas.The AgZn zeolitic imidazolate framework derived nitrogen carbon catalyst with a Ag/Zn ratio of 0.5:1 achieved the highest CO Faradaic efficiency of 52.0%with a current density of 1.15 mA·cm^(−2)at−0.5 V,a H2/CO ratio of 1-2(−0.5 to−0.7 V),and a stable catalytic activity of more than 6 h.Its activity is comparable to that of the CO_(2)-saturated NH4HCO3 electrolyte.The highly discrete Ag-N_(x)and Zn-N_(x)nodes may have combined catalytic effects in the catalysts synthesized by appropriate Ag doping and sufficient carbonization.These nodes could increase active sites of catalysts,which is conducive to the transport and adsorption of reactant CO_(2)and the stability of*COOH intermediate,thus can improve the selectivity and catalytic activity of CO.
