Using the molten salt and polyvinyl alcohol-protected reduction method,we fabricated Co3O4 octahedron-supported Au-Pd（x（AuPdy）/Co3O4;x =（0.18,0.47,and 0.96） wt%;y（Pd/Au molar ratio） =1.85-1.97） nanocatalysts.T...Using the molten salt and polyvinyl alcohol-protected reduction method,we fabricated Co3O4 octahedron-supported Au-Pd（x（AuPdy）/Co3O4;x =（0.18,0.47,and 0.96） wt%;y（Pd/Au molar ratio） =1.85-1.97） nanocatalysts.The molten salt-derived Co3O4 sample possessed well-defined octahedral morphology,with an edge length of 300 nm.The Au-Pd nanoparticles,with sizes of 2.7-3.2 nm,were uniformly dispersed on the surface of Co3O4.The 0.96（AuPd1.92）/Co3O4 sample showed the highest catalytic activity for toluene and o-xylene oxidation,and the temperature required for achieving 90%conversion of toluene and o-xylene was 180 and 187 ℃,respectively,at a space velocity of 40000 mL/（g·h）.The high catalytic performance of Co3O4 octahedron-supported Au-Pd nanocatalysts was associated with the interaction between Au-Pd nanoparticles and Co3O4 and high concentration of adsorbed oxygen species.展开更多
Single-atom catalysts(SACs),including metalmetal-bonded bimetallic ones named single-atom alloys(SAAs),have aroused significant interest in catalysis.In this article,the catalytic mechanism and bonding analysis of CO ...Single-atom catalysts(SACs),including metalmetal-bonded bimetallic ones named single-atom alloys(SAAs),have aroused significant interest in catalysis.In this article,the catalytic mechanism and bonding analysis of CO oxidation reaction on bimetallic gold–palladium(Au–Pd)model of single atom alloy Au37Pd1 are investigated by using quantum chemical calculations.The molecular geometries and adsorbate/substrate binding energies of CO@Au–Pd,O2@Au–Pd and CO/O2@Au–Pd configurations are identified.The core-shell structure is confirmed to be the most stable structure for Au–Pd SAA,where the Pd atom prefers to situate at the core site.Charge transfer from the Pd atom to the Au atoms has been confirmed to stabilize the structure.According to the binding energy and chemical bonding analysis,both CO and O2 prefer to bind to the Pd atom at the hex site with low coordination number.The formation of new co-adsorption species is identified,in which vertical and parallel bridging adsorptions of CO and O2 on the Au–Pd bonds are observed.CO oxidation on Au–Pd SAA is found to be feasible with low energy barriers and follows the Langmuir-Hinshewood(L-H)mechanism.Our work offers insights into the significant role of single atom of the SAAs in catalytic reactions and can provide evidence for designing new SAAs with high-performance catalytic activities.展开更多
Heterogeneous doping is one effective strategy for synthesizing metal alloy nanowires.Herein,the heterogeneous doping processes of Pd on the ultrathin Au nanowires were systematically modulated and investigated.Au-Pd ...Heterogeneous doping is one effective strategy for synthesizing metal alloy nanowires.Herein,the heterogeneous doping processes of Pd on the ultrathin Au nanowires were systematically modulated and investigated.Au-Pd alloy nanowires with various morphologies and lattice structures can be obtained by adjusting the morphology of the precursor Au nanowires and the kinetics of the heterogeneous doping processes.The effects of the rate of Pd reduction and the concentration of the ligand oleylamine(OAm)on the Pd deposition and alloying mode were articulated.Generally,as the Pd deposition rate decreases,the Pd deposition and alloying mode switches from the island-forming Stransky–Krastanov(SK)mode to the epitaxial Frank-van der Merwe(FM)mode,and eventually to an unconventional twisting alloying mode,where the interdiffusion of Pd and Au causes drastic rearrangement of the lattice structure and formation of helical structures.The kinetics-related variation of alloying mode could also be observed in the Au-Ag nanowires,demonstrating a general design principle for the synthesis of alloy nanostructures.In addition,the electrocatalytic performance of various Au-Pd nanowires was evaluated,and the alloy nanowire formed via the SK mode was found to be an excellent electrocatalyst for oxygen reduction and ethanol oxidation.展开更多
Selective oxidation of propane to acetone(AC)with H_(2) and O_(2) provides a direct route to convert low-cost propane into valueadded products.Unfortunately,the catalytic activity of conventional Au/Ti-based catalysts...Selective oxidation of propane to acetone(AC)with H_(2) and O_(2) provides a direct route to convert low-cost propane into valueadded products.Unfortunately,the catalytic activity of conventional Au/Ti-based catalysts is constrained by the high energy barrier for H_(2) dissociation.Herein,uncalcined TS-1 supported Au-Pd bimetallic catalysts were prepared,and the relationship between the active-site structure and corresponding performance in the selective oxidation of propane with H_(2) and O_(2) in the gas phase was systematically investigated.In contrast to the liquid-phase reaction,trace Pd alloyed with Au triggered an increase in both catalytic activity and selectivity,in which Au_(20)-Pd_(1)/TS-1-B catalyst exhibited excellent activity(170 gAC·h^(−1)·kgcat^(−1))and AC selectivity(90.6%),much higher than those of the Au/TS-1-B catalyst(AC formation rate of 100 gAC·h^(−1)·kgcat^(−1)and AC selectivity of 86.3%).It was found that Pd was gradually isolated into monomers with the increase of Au/Pd molar ratio,and the synergy between Pd single atoms and Au improved the catalytic performance via enhancing hydrogen dissociation and modulating the electronic structure of Au.Furthermore,the reaction conditions were optimized based on the kinetics studies and the Au_(20)-Pd_(1)/TS-1-B catalyst exhibited enhanced H_(2) selectivity(45%)and long-term stability(over 130 h).The insights gained here can offer valuable guidance for the design of Au-Pd catalysts applicable to other gas-phase oxidation reactions.展开更多
In wet chemical syntheses of noble metal nanocrystals,surfactants play crucial roles in regulating their morphology.To date,more attention has been paid to the effect of the surfactant on the surface energy of crystal...In wet chemical syntheses of noble metal nanocrystals,surfactants play crucial roles in regulating their morphology.To date,more attention has been paid to the effect of the surfactant on the surface energy of crystal facets,while less attention has been paid to its effect on the growth kinetics.In this paper,using the growth of Au-Pd alloy nanocrystals as an example,we demonstrate that different concentration of surfactant hexadecyltrimethyl ammonium chloride(CTAC)may cause the different packing density of CTA+bilayers on different sites(face,edge or vertex)of crystallite surface,which would change the crystal growth kinetics and result in preferential crystal growth along the edge or vertex of crystallites.The unique shape evolution from trisoctahedron to excavated rhombic dodecahedron and multipod structure for Au-Pd alloy nanocrystals was successfully achieved by simply adjusting the concentration of CTAC.These results help to understand the effect of surfactants on the shape evolution of nanocrystals and open up avenues to the rational synthesis of nanocrystals with the thermodynamically unfavorable morphologies.展开更多
Nano-sized Au and Pd catalysts are favorable for oxidations with molecular oxygen, and the preparation of this kind of nanoparticles with high catalytic activities is strongly desirable. We report a successful synthes...Nano-sized Au and Pd catalysts are favorable for oxidations with molecular oxygen, and the preparation of this kind of nanoparticles with high catalytic activities is strongly desirable. We report a successful synthesis of bimetal- lic Au-Pd nanoparticles with rich edge and comer sites on unique support of Mg-AI mixed oxides （Au-Pd/MAO）, which are favorable for producing metal nanoparticles with high degree of coordinative unsaturation of metal atoms The systematic microscopic characterizations confirm the bimetallic Au-Pd nanoparticles are present as Au-Pd alloy The irregular shape of the bimetallic nanoparticles are directly observed in HRTEM images. As we expected, Au-Pd/MAO gives very excellent catalytic performances in the aerobic oxidation of benzyl alcohol and glycerol. For example, Au-Pd/MAO shows very high TOF of 91000 h i at 433 K with molecular oxygen at air pressure in solvent-free oxidation of benzyl alcohol; this catalyst also shows relatively high selectivity for tartronic acid （TA- RAC, 36.6%） at high conversion （98.5%） in aerobic oxidation of glycerol. The superior catalytic properties of Au-Pd/MAO would be potentially important tbr production of fine chemicals.展开更多
A successful approach to assemble Au core Pd shell （Au@Pd） nanoparticles on the surface of multi-walled carbon nanotubes functionalized by methylene blue （MB） （Au@Pd/fuv-MWCNTs） was reported. In this method, MWC...A successful approach to assemble Au core Pd shell （Au@Pd） nanoparticles on the surface of multi-walled carbon nanotubes functionalized by methylene blue （MB） （Au@Pd/fuv-MWCNTs） was reported. In this method, MWCNTs were functionalized under ultraviolet irradiation. UV-Vis analysis and high-angle annular dark-field trans- mission electron microscope （HAADF-TEM） image prove that core-shell structure of Au@Pd nanoparticles forms. TEM results indicate that Au@Pd nanoparticles （ - 5.2 nm） are well-dispersed on the surface of fuv-MWCNTs. X-ray photoelectron spectroscopy （XPS） reveals that ultraviolet irradiation can promote the interaction between Au@Pd nanoparticles and the functional groups on the surface of MWCNTs. Cyclic voltammograms （CV）, chronoampero- grams （CA）, and electrochemical impedance spectroscopy （EIS） results demonstrate that the Au@Pd/fuv-MWCNTs catalysts show excellent electrocatalytic performance for methanol oxidation in alkaline media. The catalytic activity of the Au@Pd/fuv-MWCNTs is ~ 2 times higher than that of the commercial Pd/C catalysts. This is mostly attributed to that ultraviolet irradiation can make the moieties of MB provide a uniform surface with active and anchoring sites, and improves the functional effect of MB on the surface of MWCNTs. Especially, ultraviolet irradiation modifies electronic structure of Pd and is beneficial for the enhance- ment of catalytic activity.展开更多
Surface-enhanced Raman spectroscopy(SERS), a powerful surface vibrational spectroscopic technique, is ideally suited for in situ monitoring the chemical transformations occurred at surfaces and/or interfaces.For in si...Surface-enhanced Raman spectroscopy(SERS), a powerful surface vibrational spectroscopic technique, is ideally suited for in situ monitoring the chemical transformations occurred at surfaces and/or interfaces.For in situ SERS monitoring, a platform integrated both plasmonic and catalytic activity is a prerequisite. Here, we fabricate a bifunctional Au-Pd nanocoronal film for in situ SERS monitoring Suzuki-Miyaura cross-coupling reaction. This excellent bifunctional substrate leads to the coupling of high catalytic activity with a strong SERS effect at the center of two adjacent Au cores and shows fine reproducibility and stability of SERS signals. During investigating the Suzuki reaction with in situ SERS, we found two distinct catalytic kinetic processes resulted from two disparate catalytic sites on a Au-Pd nanocoronal. Comparing with conventional analytical techniques, this work provides a novel approach for studying Suzuki reactions at surfaces and/or interfaces with in situ SERS.展开更多
Bimetallic Au/Pd nanoparticles were prepared and used to catalyze oxidation of alcohols in the poly(ethylene glycol) (PEG)/CO_(2) biphasic system using O2 as the oxidant without adding any base.The catalytic activity ...Bimetallic Au/Pd nanoparticles were prepared and used to catalyze oxidation of alcohols in the poly(ethylene glycol) (PEG)/CO_(2) biphasic system using O2 as the oxidant without adding any base.The catalytic activity of Au/Pd bimetal with different mole ratios was studied using benzyl alcohol as the substrate.It was found that bimetallic Au/Pd nanoparticles with Au:Pd=1:3.5 had higher catalytic activity than monometallic Au,Pd and the bimetallic Au/Pd nanoparticles with other molar ratios.The effect of CO_(2) pressure on the oxidation of benzyl alcohol and 1-phenylethanol in PEG/CO_(2) was investigated.It was demonstrated that CO_(2) pressure could be used to tune the conversion and selectivity of the reactions effectively.α,β-Unsaturated alcohols were also studied and found to be more reactive than benzyl alcohol and 1-phenylethanol.Recycling experiments showed that the Au/Pd/PEG/CO_(2) catalytic system could be recycled at least four times without reducing the activity.In addition,the catalytic system is clean and the products can be separated easily.展开更多
Gold-doped palladium clusters, Au2Pdn （n=1～4）, are investigated using the density functional method B3LYP with relativistic effective core potentials （RECP） and LANL2DZ basis set. The possible geometrical configu...Gold-doped palladium clusters, Au2Pdn （n=1～4）, are investigated using the density functional method B3LYP with relativistic effective core potentials （RECP） and LANL2DZ basis set. The possible geometrical configurations with their electronic states are determined, and the stability trend is investigated. Several low-lying isomers are determined, and many of them are in electronic configurations with a high-spin multiplicity. Our results indicate that the palladium-gold interaction is strong enough to modify the known pattern of bare palladium clusters, and the lower stability as the structures grow in size. The present calculations are useful to understanding the enhanced catalytic activity and selectivity gained by using gold-doped palladium catalyst.展开更多
The effects of palladium addition and the reduction methods on Au/TiO2 were investigated. Pd was loaded on TiO2 firstly by incipient-wetness impregnation, Au was then loaded by deposition-precipitation method. The nom...The effects of palladium addition and the reduction methods on Au/TiO2 were investigated. Pd was loaded on TiO2 firstly by incipient-wetness impregnation, Au was then loaded by deposition-precipitation method. The nominal loadings of Au and Pd were 1 wt% and 0.01 wt%. The bimetallic catalysts were reduced by heating at 453 K, by flowing H2 at 423 K, or by NaBH4 at 298 K. The catalysts were characterized by ICP, XRD, TEM, HRTEM, TPR and XPS. Hydrogenation of p-chloronitrobenzene was carried out at 1.2 MPa H2 pressure and 353 K. The results showed that even adding very small amount of Pd could enhance activity and selectivity of p-chloroaniline significantly. Pd and Au formed alloy and Pd could donate partial electron to Au. Pd metal on the surface of alloy could adsorb hydrogen and enhanced the activity. The pretreatment methods did not change particle size significantly, all were below 4 nm. The sample reduced by NaBH4 could have higher concentration of Au0 and sustain small Au particle size, resulting in high activity.展开更多
基金supported by the National Natural Science Foundation of China (21377008, 21477005, U1507108)National High Technology Re-search and Development Program of China (2015AA034603)+1 种基金Beijing Nova Program (Z141109001814106)Natural Science Foundation of Bei-jing Municipal Commission of Education (KM201410005008)~~
文摘Using the molten salt and polyvinyl alcohol-protected reduction method,we fabricated Co3O4 octahedron-supported Au-Pd（x（AuPdy）/Co3O4;x =（0.18,0.47,and 0.96） wt%;y（Pd/Au molar ratio） =1.85-1.97） nanocatalysts.The molten salt-derived Co3O4 sample possessed well-defined octahedral morphology,with an edge length of 300 nm.The Au-Pd nanoparticles,with sizes of 2.7-3.2 nm,were uniformly dispersed on the surface of Co3O4.The 0.96（AuPd1.92）/Co3O4 sample showed the highest catalytic activity for toluene and o-xylene oxidation,and the temperature required for achieving 90%conversion of toluene and o-xylene was 180 and 187 ℃,respectively,at a space velocity of 40000 mL/（g·h）.The high catalytic performance of Co3O4 octahedron-supported Au-Pd nanocatalysts was associated with the interaction between Au-Pd nanoparticles and Co3O4 and high concentration of adsorbed oxygen species.
基金supported by the National Natural Science Foundation of China (91645203,21433005,and 21590792)the Tsinghua Xuetang Talents Program for providing computational resources+1 种基金the support from DGAPA-UNAM (IN108817)Conacyt-Mexico (285821)
文摘Single-atom catalysts(SACs),including metalmetal-bonded bimetallic ones named single-atom alloys(SAAs),have aroused significant interest in catalysis.In this article,the catalytic mechanism and bonding analysis of CO oxidation reaction on bimetallic gold–palladium(Au–Pd)model of single atom alloy Au37Pd1 are investigated by using quantum chemical calculations.The molecular geometries and adsorbate/substrate binding energies of CO@Au–Pd,O2@Au–Pd and CO/O2@Au–Pd configurations are identified.The core-shell structure is confirmed to be the most stable structure for Au–Pd SAA,where the Pd atom prefers to situate at the core site.Charge transfer from the Pd atom to the Au atoms has been confirmed to stabilize the structure.According to the binding energy and chemical bonding analysis,both CO and O2 prefer to bind to the Pd atom at the hex site with low coordination number.The formation of new co-adsorption species is identified,in which vertical and parallel bridging adsorptions of CO and O2 on the Au–Pd bonds are observed.CO oxidation on Au–Pd SAA is found to be feasible with low energy barriers and follows the Langmuir-Hinshewood(L-H)mechanism.Our work offers insights into the significant role of single atom of the SAAs in catalytic reactions and can provide evidence for designing new SAAs with high-performance catalytic activities.
基金support from the National Natural Science Foundation of China(Nos.21703104 and 91956109)Zhejiang Provincial Natural Science Foundation of China(No.2022XHSJJ002)+2 种基金Hangzhou Municipal Funding(No.TD2022004)Nanjing Tech University(No.39837131)SICAM Fellowship from Jiangsu National Synergetic Innovation Centre for Advanced Materials。
文摘Heterogeneous doping is one effective strategy for synthesizing metal alloy nanowires.Herein,the heterogeneous doping processes of Pd on the ultrathin Au nanowires were systematically modulated and investigated.Au-Pd alloy nanowires with various morphologies and lattice structures can be obtained by adjusting the morphology of the precursor Au nanowires and the kinetics of the heterogeneous doping processes.The effects of the rate of Pd reduction and the concentration of the ligand oleylamine(OAm)on the Pd deposition and alloying mode were articulated.Generally,as the Pd deposition rate decreases,the Pd deposition and alloying mode switches from the island-forming Stransky–Krastanov(SK)mode to the epitaxial Frank-van der Merwe(FM)mode,and eventually to an unconventional twisting alloying mode,where the interdiffusion of Pd and Au causes drastic rearrangement of the lattice structure and formation of helical structures.The kinetics-related variation of alloying mode could also be observed in the Au-Ag nanowires,demonstrating a general design principle for the synthesis of alloy nanostructures.In addition,the electrocatalytic performance of various Au-Pd nanowires was evaluated,and the alloy nanowire formed via the SK mode was found to be an excellent electrocatalyst for oxygen reduction and ethanol oxidation.
基金supported by the Ministry of Science and Technology of the People’s Republic of China under the Research Fund for National Key Research and Development Program of China(No.2021YFA1501403)the National Natural Science Foundation of China(Nos.22208093,22038003,and 22178100)+2 种基金the Shanghai Science and Technology Innovation Action Plan(No.22JC1403800)the Innovation Program of the Shanghai Municipal Education Commission,the Program of Shanghai Academic/Technology Research Leader(No.21XD1421000)the Fundamental Research Funds for the Central Universities.
文摘Selective oxidation of propane to acetone(AC)with H_(2) and O_(2) provides a direct route to convert low-cost propane into valueadded products.Unfortunately,the catalytic activity of conventional Au/Ti-based catalysts is constrained by the high energy barrier for H_(2) dissociation.Herein,uncalcined TS-1 supported Au-Pd bimetallic catalysts were prepared,and the relationship between the active-site structure and corresponding performance in the selective oxidation of propane with H_(2) and O_(2) in the gas phase was systematically investigated.In contrast to the liquid-phase reaction,trace Pd alloyed with Au triggered an increase in both catalytic activity and selectivity,in which Au_(20)-Pd_(1)/TS-1-B catalyst exhibited excellent activity(170 gAC·h^(−1)·kgcat^(−1))and AC selectivity(90.6%),much higher than those of the Au/TS-1-B catalyst(AC formation rate of 100 gAC·h^(−1)·kgcat^(−1)and AC selectivity of 86.3%).It was found that Pd was gradually isolated into monomers with the increase of Au/Pd molar ratio,and the synergy between Pd single atoms and Au improved the catalytic performance via enhancing hydrogen dissociation and modulating the electronic structure of Au.Furthermore,the reaction conditions were optimized based on the kinetics studies and the Au_(20)-Pd_(1)/TS-1-B catalyst exhibited enhanced H_(2) selectivity(45%)and long-term stability(over 130 h).The insights gained here can offer valuable guidance for the design of Au-Pd catalysts applicable to other gas-phase oxidation reactions.
基金supported by the National Basic Research Program of China (2015CB932301)the National Key Research and Development Program of China (2017YFA0206801)the National Natural Science Foundation of China (21333008, 21773190 and J1310024)
文摘In wet chemical syntheses of noble metal nanocrystals,surfactants play crucial roles in regulating their morphology.To date,more attention has been paid to the effect of the surfactant on the surface energy of crystal facets,while less attention has been paid to its effect on the growth kinetics.In this paper,using the growth of Au-Pd alloy nanocrystals as an example,we demonstrate that different concentration of surfactant hexadecyltrimethyl ammonium chloride(CTAC)may cause the different packing density of CTA+bilayers on different sites(face,edge or vertex)of crystallite surface,which would change the crystal growth kinetics and result in preferential crystal growth along the edge or vertex of crystallites.The unique shape evolution from trisoctahedron to excavated rhombic dodecahedron and multipod structure for Au-Pd alloy nanocrystals was successfully achieved by simply adjusting the concentration of CTAC.These results help to understand the effect of surfactants on the shape evolution of nanocrystals and open up avenues to the rational synthesis of nanocrystals with the thermodynamically unfavorable morphologies.
文摘Nano-sized Au and Pd catalysts are favorable for oxidations with molecular oxygen, and the preparation of this kind of nanoparticles with high catalytic activities is strongly desirable. We report a successful synthesis of bimetal- lic Au-Pd nanoparticles with rich edge and comer sites on unique support of Mg-AI mixed oxides （Au-Pd/MAO）, which are favorable for producing metal nanoparticles with high degree of coordinative unsaturation of metal atoms The systematic microscopic characterizations confirm the bimetallic Au-Pd nanoparticles are present as Au-Pd alloy The irregular shape of the bimetallic nanoparticles are directly observed in HRTEM images. As we expected, Au-Pd/MAO gives very excellent catalytic performances in the aerobic oxidation of benzyl alcohol and glycerol. For example, Au-Pd/MAO shows very high TOF of 91000 h i at 433 K with molecular oxygen at air pressure in solvent-free oxidation of benzyl alcohol; this catalyst also shows relatively high selectivity for tartronic acid （TA- RAC, 36.6%） at high conversion （98.5%） in aerobic oxidation of glycerol. The superior catalytic properties of Au-Pd/MAO would be potentially important tbr production of fine chemicals.
基金financially supported by the National Natural Science Foundation of China (Nos. 51164017, 51374117, and 21363012)
文摘A successful approach to assemble Au core Pd shell （Au@Pd） nanoparticles on the surface of multi-walled carbon nanotubes functionalized by methylene blue （MB） （Au@Pd/fuv-MWCNTs） was reported. In this method, MWCNTs were functionalized under ultraviolet irradiation. UV-Vis analysis and high-angle annular dark-field trans- mission electron microscope （HAADF-TEM） image prove that core-shell structure of Au@Pd nanoparticles forms. TEM results indicate that Au@Pd nanoparticles （ - 5.2 nm） are well-dispersed on the surface of fuv-MWCNTs. X-ray photoelectron spectroscopy （XPS） reveals that ultraviolet irradiation can promote the interaction between Au@Pd nanoparticles and the functional groups on the surface of MWCNTs. Cyclic voltammograms （CV）, chronoampero- grams （CA）, and electrochemical impedance spectroscopy （EIS） results demonstrate that the Au@Pd/fuv-MWCNTs catalysts show excellent electrocatalytic performance for methanol oxidation in alkaline media. The catalytic activity of the Au@Pd/fuv-MWCNTs is ~ 2 times higher than that of the commercial Pd/C catalysts. This is mostly attributed to that ultraviolet irradiation can make the moieties of MB provide a uniform surface with active and anchoring sites, and improves the functional effect of MB on the surface of MWCNTs. Especially, ultraviolet irradiation modifies electronic structure of Pd and is beneficial for the enhance- ment of catalytic activity.
基金the financial support from the National Natural Science Foundation of China (No. 22022406)the Natural Science Foundation of Tianjin (Nos. 20JCJQJC00110 and 20JCYBJC00590)+1 种基金the 111 project (No. B12015)the Haihe Laboratory of Sustainable Chemical Transformations。
文摘Surface-enhanced Raman spectroscopy(SERS), a powerful surface vibrational spectroscopic technique, is ideally suited for in situ monitoring the chemical transformations occurred at surfaces and/or interfaces.For in situ SERS monitoring, a platform integrated both plasmonic and catalytic activity is a prerequisite. Here, we fabricate a bifunctional Au-Pd nanocoronal film for in situ SERS monitoring Suzuki-Miyaura cross-coupling reaction. This excellent bifunctional substrate leads to the coupling of high catalytic activity with a strong SERS effect at the center of two adjacent Au cores and shows fine reproducibility and stability of SERS signals. During investigating the Suzuki reaction with in situ SERS, we found two distinct catalytic kinetic processes resulted from two disparate catalytic sites on a Au-Pd nanocoronal. Comparing with conventional analytical techniques, this work provides a novel approach for studying Suzuki reactions at surfaces and/or interfaces with in situ SERS.
基金the National Natural Science Foundation of China (20973177 & 20932002)Ministry of Science and Technology of China (2006CB202504)Chinese Academy of Sciences (KJCX2. YW.H16) for financial supports
文摘Bimetallic Au/Pd nanoparticles were prepared and used to catalyze oxidation of alcohols in the poly(ethylene glycol) (PEG)/CO_(2) biphasic system using O2 as the oxidant without adding any base.The catalytic activity of Au/Pd bimetal with different mole ratios was studied using benzyl alcohol as the substrate.It was found that bimetallic Au/Pd nanoparticles with Au:Pd=1:3.5 had higher catalytic activity than monometallic Au,Pd and the bimetallic Au/Pd nanoparticles with other molar ratios.The effect of CO_(2) pressure on the oxidation of benzyl alcohol and 1-phenylethanol in PEG/CO_(2) was investigated.It was demonstrated that CO_(2) pressure could be used to tune the conversion and selectivity of the reactions effectively.α,β-Unsaturated alcohols were also studied and found to be more reactive than benzyl alcohol and 1-phenylethanol.Recycling experiments showed that the Au/Pd/PEG/CO_(2) catalytic system could be recycled at least four times without reducing the activity.In addition,the catalytic system is clean and the products can be separated easily.
基金The project supported by the Foundation of the Education Department of Sichuan Province of China under Grant No. 2004A117
文摘Gold-doped palladium clusters, Au2Pdn （n=1～4）, are investigated using the density functional method B3LYP with relativistic effective core potentials （RECP） and LANL2DZ basis set. The possible geometrical configurations with their electronic states are determined, and the stability trend is investigated. Several low-lying isomers are determined, and many of them are in electronic configurations with a high-spin multiplicity. Our results indicate that the palladium-gold interaction is strong enough to modify the known pattern of bare palladium clusters, and the lower stability as the structures grow in size. The present calculations are useful to understanding the enhanced catalytic activity and selectivity gained by using gold-doped palladium catalyst.
文摘The effects of palladium addition and the reduction methods on Au/TiO2 were investigated. Pd was loaded on TiO2 firstly by incipient-wetness impregnation, Au was then loaded by deposition-precipitation method. The nominal loadings of Au and Pd were 1 wt% and 0.01 wt%. The bimetallic catalysts were reduced by heating at 453 K, by flowing H2 at 423 K, or by NaBH4 at 298 K. The catalysts were characterized by ICP, XRD, TEM, HRTEM, TPR and XPS. Hydrogenation of p-chloronitrobenzene was carried out at 1.2 MPa H2 pressure and 353 K. The results showed that even adding very small amount of Pd could enhance activity and selectivity of p-chloroaniline significantly. Pd and Au formed alloy and Pd could donate partial electron to Au. Pd metal on the surface of alloy could adsorb hydrogen and enhanced the activity. The pretreatment methods did not change particle size significantly, all were below 4 nm. The sample reduced by NaBH4 could have higher concentration of Au0 and sustain small Au particle size, resulting in high activity.
