A series of bimetallic Pd-Pb catalysts with a constant Pd content of 1 wt%and Pb/Pd atomic ratio from 0 to 1.6 supported on γ-Al2O3 were prepared and used for glycerol oxidation with H2O2 as the oxidizing agent at at...A series of bimetallic Pd-Pb catalysts with a constant Pd content of 1 wt%and Pb/Pd atomic ratio from 0 to 1.6 supported on γ-Al2O3 were prepared and used for glycerol oxidation with H2O2 as the oxidizing agent at atmospheric pressure,45℃ and pH =11.The morphology and dispersion of the catalysts were characterized by scanning electron microscopy-energy dispersive X-ray spectroscopy（SEM-EDX） and transmission electron microscopy（TEM）.The presence of an alloy phase in the bimetallic catalyst was detected by X-ray photoelectron spectroscopy（XPS）.Glycerol conversion obtained with the monometallic Pd catalyst was 19%,which was increased to 100%with the addition of Pb.The four bimetallic PdPb catalysts were able to oxidize glycerol to dihydroxyacetone（DIHA） and the selectivity to DIHA reached 59%,58%,34%and 25%for PdPb0.25,PdPb0.50,PdPb1.00 and PdPbl.60 catalysts,respectively.展开更多
TiO2‐supported Pd‐Sb bimetallic catalysts were prepared and evaluated for the direct synthesis of H2O2 at ambient pressure.The addition of Sb to Pd significantly enhanced catalytic performance,and a Pd50Sb catalyst ...TiO2‐supported Pd‐Sb bimetallic catalysts were prepared and evaluated for the direct synthesis of H2O2 at ambient pressure.The addition of Sb to Pd significantly enhanced catalytic performance,and a Pd50Sb catalyst showed the greatest selectivity of up to 73%.Sb promoted the dispersion of Pd on TiO2,as evidenced by transmission electron microscopy and X‐ray diffraction.X‐ray photoelectron spectroscopy indicated that the oxidation of Pd was suppressed by Sb.In addition,Sb2O3 layers were formed and partially wrapped the surfaces of Pd catalysts,thus suppressing the activation of H2 and subsequent hydrogenation of H2O2.In situ diffuse reflection infrared Fourier transform spectroscopy for CO adsorption suggested that Sb homogenously located on the surface of Pd‐Sb catalysts and isolated contiguous Pd sites,resulting in the rise of the ratio of Pd monomer sites that are favorable for H2O2 formation.As a result,the Sb modified Pd surfaces significantly enhanced the non‐dissociative activation of O2 and H2O2 selectivity.展开更多
The development of active and durable non-Pt electrocatalysts with well-defined microstructure is of great importance to both fuel cell applications and fundamental understanding.Herein,we report a surface-doping proc...The development of active and durable non-Pt electrocatalysts with well-defined microstructure is of great importance to both fuel cell applications and fundamental understanding.Herein,we report a surface-doping process to prepare well-defined W-doped Pd nanocubes with a tunable atomic percent of W from 0 to 1.5%by using the Pd nanocubes as seeds.The obtained 1.2%W-doped Pd nanocubes/C exhibited greatly enhanced electrocatalytic performance toward oxygen reduction reaction in alkaline media,presenting an enhancement factor of 4.7 in specific activity and 2.5 in mass activity compared to the activity of a commercial Pt/C catalyst.The downshift of the d-band center due to a negative charge transfer from W to Pd intrinsically accounts for such improvement in activity by weakening the adsorption of reaction intermediates.Also,the 1.2%W-doped Pd nanocubes/C showed superior catalytic properties for the ethanol oxidation reaction,showing great potential for serving as a bifunctional electrocatalyst in fuel cells.展开更多
The one-pot synthesis of methyl isobutyl ketone（MIBK） from acetone using multifunctional catalysts is an important sustainable organic synthesis method with high atom and energy efficiency.Herein. we report a series...The one-pot synthesis of methyl isobutyl ketone（MIBK） from acetone using multifunctional catalysts is an important sustainable organic synthesis method with high atom and energy efficiency.Herein. we report a series of Pd supported on mixed metal oxide（MMO） catalysts with controllable acidic/basic/metallic sites on the surface. We study the relationship between the nature, synergy,and proximity of active sites and the catalytic performance of the multifunctional catalyst in the tandem reaction, in detail. In the existence of Lewis acid and base sites, the catalysts with medium-strength acidic/basic sites show preferred activity and/or MIBK selectivity. For multifunctional catalysts, the catalytic properties are more than just a collection of active sites, and the Pd/Mg_3Al-MMO catalyst possessing 0.1% Pd loading and ~0.4 acid/base molar ratio exhibits the optimal 42.1% acetone conversion and 37.2% MIBK yield, which is among the best reported so far for this tandem reaction under similar conditions. Moreover, the proximity test indicates that the intimate distance between acidic/basic/metallic sites can greatly shorten the diffusion time of the intermediate species from each active site, leading to an enhancement in the catalytic performance.展开更多
Bimetallic palladium-gold （PdAu） catalysts have better catalytic performance than monometallic catalysts for many applications. PdAu catalysts with controlled nanostructures and enhanced activi- ties have been exten...Bimetallic palladium-gold （PdAu） catalysts have better catalytic performance than monometallic catalysts for many applications. PdAu catalysts with controlled nanostructures and enhanced activi- ties have been extensively studied but their syntheses require multiple and occasionally complicated steps, In this work, we demonstrated that supported PdAu catalysts could be simply prepared by doping a supported Pd catalyst with gold through wet impregnation and calcination. Resulting PdAu-on-carbon （PdAu/C） catalysts were tested for the room-temperature, aqueous-phase hydro- dech/orination of trichloroethene. The most active PdAu/C catalyst （Pd 1.0 wt%, Au 1.1 wt%, dried/air/H2 process] had an initial turnover frequency （TOF] of 34.0×10^-2 mOITcE mOled-1 S-1, which was 〉15 times higher than monometallic Pd/C （Pd 1,0 wt%, initial TOF of 2.2 ×10^-2 molTCE molpd^-1s^-1）. Through X-ray absorption spectroscopy, the gold kept Pd from oxidizing under calcination at 400℃. Probable nanostructure evolution pathways are proposed to explain the observed catalysis,展开更多
The Solvated Metal Atom Impregnation (SMAI) technique was employed to prepare macroporous resin immobilized Pd--Cu bimetallic cluster catalysts. The X--ray diffraction (XRD) and transmission electron micrograph (TEM) ...The Solvated Metal Atom Impregnation (SMAI) technique was employed to prepare macroporous resin immobilized Pd--Cu bimetallic cluster catalysts. The X--ray diffraction (XRD) and transmission electron micrograph (TEM) showed that Pd--Cu alloy was formed and the particle sizes of Pd--Cu clusters were very small, with average diameters <3nm. X--ray photoelectron spectroscopy indicated that both Pd and Cu were in zero--valent state. The catalytic activities of the macroporous resin immobilized Pd--Cu catalysts in hydrogenation of 4--methyl--3--penten--2--one were much greater than that of the carbon supported Pd--Cu catalysts.展开更多
A simple and efficient solution-based method for the synthesis of Pd-Ni bimetallic nanoparticles （NPs） has been developed. A series of Pd-Ni bimetallic NPs were readily achieved by reduction of PdC12 and Ni（acac）2...A simple and efficient solution-based method for the synthesis of Pd-Ni bimetallic nanoparticles （NPs） has been developed. A series of Pd-Ni bimetallic NPs were readily achieved by reduction of PdC12 and Ni（acac）2 （acac = acetyl- acetonate） in the presence of oleylamine （OAm）, oleic acid （OA） and benzyl alcohol. Furthermore, by using high-resolution transmission electron microscopy （HRTEM）, energy-dispersive spectrometry （EDS） mapping and X-ray diffraction （XRD）, we demonstrate that the as-prepared Pd-Ni bimetallic NPs have core-shell structures with a Pd-rich core and a Ni-rich shell. In addition, the as-obtained Pd-Ni bimetallic NPs with varying compositions show excellent catalytic activities in the Miyaura-Suzuki reaction. When the nickel molar percentage was 0.23 to 0.65, the conversion with the as-obtained Pd-Ni bimetallic catalysts was above 90%. It is believed that this strategy can be employed to produce a variety of other well-defined core-shell type multimetallic nanostructures.展开更多
The transition-metal-catalyzed copolymerization of olefins with polar comonomers is a direct strategy to access polar-functionalized polyolefins in an economical manner.Due to the intrinsic poisoning effect of polar g...The transition-metal-catalyzed copolymerization of olefins with polar comonomers is a direct strategy to access polar-functionalized polyolefins in an economical manner.Due to the intrinsic poisoning effect of polar groups towards Lewis acidic metal centers and the drastic reactivity differences of polar comonomers versus non-polar olefins,it is challenging to develop catalysts that provide the desired polymer molecular weight,comonomer incorporation,and activity.In this contribution,we tackle this issue from a comonomer perspective using 5,6-disubstituted norbornenes,which are highly versatile,easily accessible,inexpensive,and capable of introducing two functional groups in a single insertion.More importantly,they are only mildly poisoning due to the presence of long spacers between double bonds and polar groups,and are not prone to b-hydride elimination due to their cyclic structures.As strong pdonors,they can competitively bind to metal centers versus olefins.Indeed,phosphine-sulfonate palladium catalysts can catalyze the copolymerization of ethylene with 5,6-disubstituted norbornenes and simultaneously achieve a high polymerization activity,copolymer molecular weight,and comonomer incorporation.The practicality of this system was demonstrated by studying the properties of the resulting polymers,copolymerization in hydrocarbon solvents or in bulk,recovery/utilization of unreacted comonomer,molecular weight modulation,and large-scale synthesis.展开更多
基金supported by the National Basic Research Program of China(973 Program,2011CB201400)the National Natural Science Foundation of China(21173008,21373019,21433001)~~
基金supported by CONICET(PIP 0276)UNLP(Projects X 700)+1 种基金UNNOBA(SIB 2924/14)Ministry of Education and Sports(Call "Jorge Sabato" Project 44-144-415),Argentina
文摘A series of bimetallic Pd-Pb catalysts with a constant Pd content of 1 wt%and Pb/Pd atomic ratio from 0 to 1.6 supported on γ-Al2O3 were prepared and used for glycerol oxidation with H2O2 as the oxidizing agent at atmospheric pressure,45℃ and pH =11.The morphology and dispersion of the catalysts were characterized by scanning electron microscopy-energy dispersive X-ray spectroscopy（SEM-EDX） and transmission electron microscopy（TEM）.The presence of an alloy phase in the bimetallic catalyst was detected by X-ray photoelectron spectroscopy（XPS）.Glycerol conversion obtained with the monometallic Pd catalyst was 19%,which was increased to 100%with the addition of Pb.The four bimetallic PdPb catalysts were able to oxidize glycerol to dihydroxyacetone（DIHA） and the selectivity to DIHA reached 59%,58%,34%and 25%for PdPb0.25,PdPb0.50,PdPb1.00 and PdPbl.60 catalysts,respectively.
基金supported by the National Natural Science Foundation of China(91534127,U1463205)the Innovation Scientists and Technicians Troop Construction Projects of Henan Provincethe Chinese Education Ministry 111 Project(B08021)~~
文摘TiO2‐supported Pd‐Sb bimetallic catalysts were prepared and evaluated for the direct synthesis of H2O2 at ambient pressure.The addition of Sb to Pd significantly enhanced catalytic performance,and a Pd50Sb catalyst showed the greatest selectivity of up to 73%.Sb promoted the dispersion of Pd on TiO2,as evidenced by transmission electron microscopy and X‐ray diffraction.X‐ray photoelectron spectroscopy indicated that the oxidation of Pd was suppressed by Sb.In addition,Sb2O3 layers were formed and partially wrapped the surfaces of Pd catalysts,thus suppressing the activation of H2 and subsequent hydrogenation of H2O2.In situ diffuse reflection infrared Fourier transform spectroscopy for CO adsorption suggested that Sb homogenously located on the surface of Pd‐Sb catalysts and isolated contiguous Pd sites,resulting in the rise of the ratio of Pd monomer sites that are favorable for H2O2 formation.As a result,the Sb modified Pd surfaces significantly enhanced the non‐dissociative activation of O2 and H2O2 selectivity.
基金supported by Collaborative Innovation Center of Suzhou Nano ScienceTechnology, MOST of China (2014CB932700)+5 种基金the National Natural Science Foundation of China (21603208, 21573206)Key Research Program of Frontier Sciences of the CAS (QYZDBSSW-SLH017)Anhui Provincial Key Scientific and Technological Project (1704a0902013)Major Program of Development Foundation of Hefei Center for Physical Science and Technology (2017FXZY002)Fundamental Research Funds for the Central UniversitiesCAS-TWAS president’s fellowship~~
文摘The development of active and durable non-Pt electrocatalysts with well-defined microstructure is of great importance to both fuel cell applications and fundamental understanding.Herein,we report a surface-doping process to prepare well-defined W-doped Pd nanocubes with a tunable atomic percent of W from 0 to 1.5%by using the Pd nanocubes as seeds.The obtained 1.2%W-doped Pd nanocubes/C exhibited greatly enhanced electrocatalytic performance toward oxygen reduction reaction in alkaline media,presenting an enhancement factor of 4.7 in specific activity and 2.5 in mass activity compared to the activity of a commercial Pt/C catalyst.The downshift of the d-band center due to a negative charge transfer from W to Pd intrinsically accounts for such improvement in activity by weakening the adsorption of reaction intermediates.Also,the 1.2%W-doped Pd nanocubes/C showed superior catalytic properties for the ethanol oxidation reaction,showing great potential for serving as a bifunctional electrocatalyst in fuel cells.
文摘The one-pot synthesis of methyl isobutyl ketone（MIBK） from acetone using multifunctional catalysts is an important sustainable organic synthesis method with high atom and energy efficiency.Herein. we report a series of Pd supported on mixed metal oxide（MMO） catalysts with controllable acidic/basic/metallic sites on the surface. We study the relationship between the nature, synergy,and proximity of active sites and the catalytic performance of the multifunctional catalyst in the tandem reaction, in detail. In the existence of Lewis acid and base sites, the catalysts with medium-strength acidic/basic sites show preferred activity and/or MIBK selectivity. For multifunctional catalysts, the catalytic properties are more than just a collection of active sites, and the Pd/Mg_3Al-MMO catalyst possessing 0.1% Pd loading and ~0.4 acid/base molar ratio exhibits the optimal 42.1% acetone conversion and 37.2% MIBK yield, which is among the best reported so far for this tandem reaction under similar conditions. Moreover, the proximity test indicates that the intimate distance between acidic/basic/metallic sites can greatly shorten the diffusion time of the intermediate species from each active site, leading to an enhancement in the catalytic performance.
基金supported by the National Science Foundation,United States(EEC-0647452)the Welch Foundation(C-1676)~~
文摘Bimetallic palladium-gold （PdAu） catalysts have better catalytic performance than monometallic catalysts for many applications. PdAu catalysts with controlled nanostructures and enhanced activi- ties have been extensively studied but their syntheses require multiple and occasionally complicated steps, In this work, we demonstrated that supported PdAu catalysts could be simply prepared by doping a supported Pd catalyst with gold through wet impregnation and calcination. Resulting PdAu-on-carbon （PdAu/C） catalysts were tested for the room-temperature, aqueous-phase hydro- dech/orination of trichloroethene. The most active PdAu/C catalyst （Pd 1.0 wt%, Au 1.1 wt%, dried/air/H2 process] had an initial turnover frequency （TOF] of 34.0×10^-2 mOITcE mOled-1 S-1, which was 〉15 times higher than monometallic Pd/C （Pd 1,0 wt%, initial TOF of 2.2 ×10^-2 molTCE molpd^-1s^-1）. Through X-ray absorption spectroscopy, the gold kept Pd from oxidizing under calcination at 400℃. Probable nanostructure evolution pathways are proposed to explain the observed catalysis,
文摘The Solvated Metal Atom Impregnation (SMAI) technique was employed to prepare macroporous resin immobilized Pd--Cu bimetallic cluster catalysts. The X--ray diffraction (XRD) and transmission electron micrograph (TEM) showed that Pd--Cu alloy was formed and the particle sizes of Pd--Cu clusters were very small, with average diameters <3nm. X--ray photoelectron spectroscopy indicated that both Pd and Cu were in zero--valent state. The catalytic activities of the macroporous resin immobilized Pd--Cu catalysts in hydrogenation of 4--methyl--3--penten--2--one were much greater than that of the carbon supported Pd--Cu catalysts.
文摘A simple and efficient solution-based method for the synthesis of Pd-Ni bimetallic nanoparticles （NPs） has been developed. A series of Pd-Ni bimetallic NPs were readily achieved by reduction of PdC12 and Ni（acac）2 （acac = acetyl- acetonate） in the presence of oleylamine （OAm）, oleic acid （OA） and benzyl alcohol. Furthermore, by using high-resolution transmission electron microscopy （HRTEM）, energy-dispersive spectrometry （EDS） mapping and X-ray diffraction （XRD）, we demonstrate that the as-prepared Pd-Ni bimetallic NPs have core-shell structures with a Pd-rich core and a Ni-rich shell. In addition, the as-obtained Pd-Ni bimetallic NPs with varying compositions show excellent catalytic activities in the Miyaura-Suzuki reaction. When the nickel molar percentage was 0.23 to 0.65, the conversion with the as-obtained Pd-Ni bimetallic catalysts was above 90%. It is believed that this strategy can be employed to produce a variety of other well-defined core-shell type multimetallic nanostructures.
基金the National Natural Science Foundation of China(52025031,21690071,U19B6001,and U1904212)K.C.Wong Education Foundation。
文摘The transition-metal-catalyzed copolymerization of olefins with polar comonomers is a direct strategy to access polar-functionalized polyolefins in an economical manner.Due to the intrinsic poisoning effect of polar groups towards Lewis acidic metal centers and the drastic reactivity differences of polar comonomers versus non-polar olefins,it is challenging to develop catalysts that provide the desired polymer molecular weight,comonomer incorporation,and activity.In this contribution,we tackle this issue from a comonomer perspective using 5,6-disubstituted norbornenes,which are highly versatile,easily accessible,inexpensive,and capable of introducing two functional groups in a single insertion.More importantly,they are only mildly poisoning due to the presence of long spacers between double bonds and polar groups,and are not prone to b-hydride elimination due to their cyclic structures.As strong pdonors,they can competitively bind to metal centers versus olefins.Indeed,phosphine-sulfonate palladium catalysts can catalyze the copolymerization of ethylene with 5,6-disubstituted norbornenes and simultaneously achieve a high polymerization activity,copolymer molecular weight,and comonomer incorporation.The practicality of this system was demonstrated by studying the properties of the resulting polymers,copolymerization in hydrocarbon solvents or in bulk,recovery/utilization of unreacted comonomer,molecular weight modulation,and large-scale synthesis.
