A Pd-Cu catalyst, with primary B2-type phase, supported by VulcanXC-7R carbon was synthesized via a solvothermal method. The catalysts were physically and electrochemically characterized by X-ray diffraction （XRD）, ...A Pd-Cu catalyst, with primary B2-type phase, supported by VulcanXC-7R carbon was synthesized via a solvothermal method. The catalysts were physically and electrochemically characterized by X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS）, trans- mission electron microscopy （TEM） and both cyclic and linear sweep voltammetry using a rotating disk electrode （RDE）. During the RDE testing, the half-wave potential of the Pd-Cu/Vulcan catalyst was 50 mV higher compared to that of commercial Pt/C catalyst for the oxygen reduction reaction （ORR） in alkaline media. The Pd-Cu/Vulcan exhibited a specific activity of 1.27 mA/cm2 and a mass activity of 0.59 A/mgpd at 0.9 V, which were 4 and 3 times greater than that of the commercial Pt/C catalyst, respectively. The Pd-Cu/Vulcan catalyst also showed higher in-situ alkaline exchange membrane fuel cell （AEMFC） performance, with operating power densities of 1100 MW/cm2 operating on H2/O2 and 700 MW/cm2 operating on H2/Air （CO2-free）, which were markedly higher than those of the commercial Pt/C. The Pd-Cu/ Vulcan catalyst also exhibited high stability during a short-term, in-situ AEMFC durability test, with only around 11% performance loss after 30 hours of operation, an improve- ment over most AEMFCs reported in the literature to date.展开更多
Ultrathin Pd nanosheets(NSs)have great advantages in catalysis due to their large specific surface area and high percentage of under-coordinated atoms.However,the electrochemical performance still can be improved via ...Ultrathin Pd nanosheets(NSs)have great advantages in catalysis due to their large specific surface area and high percentage of under-coordinated atoms.However,the electrochemical performance still can be improved via composition-controllable growth of their solid solution.Herein,seeded alloying strategy was proposed to synthesize Pd-Cu solid solution from Pd NSs and Pd-Cu nanostructures with tunable molar ratios obtained by changing the amount of Cu precursor.As compared to the pristine Pd NSs,the Pd-Cu solid solution shows significantly enhanced methanol oxidation reaction(MOR)performance over those of Pd NSs and homemade Pd/C as the incorporation of Cu weakens the adsorption of CO intermediate on Pd in the MOR process.The choice of template is pivotal to the growth,as a shape-dependent behavior could be identified in the alloying of Cu with Pd nanosheets enclosed by{111}and{100}facets,Pd nanocubes enclosed by{100}facet,and Pd nano-tetrahedrons enclosed by{111}facet.The Pd-Cu solid solution with tunable composition can only be obtained from Pd NSs and the shape-dependent alloying process is mainly determined by the diffusion barrier and the minimum diffusion depth of the different facets.展开更多
Excessive nitrate in water is harmful to the ecological environment and human health.Electrocatalytic reduction is a promising technology for nitrate removal.Herein,a Pd-Cu modified carbon nanotube membrane was fabric...Excessive nitrate in water is harmful to the ecological environment and human health.Electrocatalytic reduction is a promising technology for nitrate removal.Herein,a Pd-Cu modified carbon nanotube membrane was fabricated with an electrodeposition method and used to reduce nitrate in a flowthrough electrochemical reactor.The optimal potential and duration for codeposition of Pd and Cu were-0.7 V and 5 min,respectively,according to linear scan voltammetry results.The membrane obtained with a Pd:Cu ratio of 1:1 exhibited a relatively high nitrate removal efficiency and N_(2)selectivity.Nitrate was almost completely reduced(~99%)by the membrane at potentials lower than-1.2 V.However,-0.8 V was the optimal potential for nitrate reduction in terms of both nitrate removal efficiency and product selectivity.The nitrate removal efficiency was 56.2%,and the N_(2)selectivity was 23.8%for the Pd:Cu=1:1 membrane operated at-0.8 V.Nitrate removal was enhanced under acidic conditions,while N_(2)selectivity was decreased.The concentrations of Cl-ions and dissolved oxygen showed little effect on nitrate reduction.The mass transfer rate constant was greatly improved by 6.6 times from 1.14×10^(-3)m/h at a membrane flux of 1 L/(m^(2)·h)to 8.71×10^(-3)m/h at a membrane flux of 15 L/(m^(2)·h),which resulted in a significant increase in the nitrate removal rate from 13.6 to 133.5 mg/(m^(2)·h).These findings show that the Pd-Cu modified CNT membrane is an efficient material for nitrate reduction.展开更多
A novel approach to the synthesis of 4-phenylethynylphthalic anhydride has been described.The target compound was synthesized by Pd/Cu catalyzed Sonogashira coupling reaction between phenylacetylene and 4-bromophthali...A novel approach to the synthesis of 4-phenylethynylphthalic anhydride has been described.The target compound was synthesized by Pd/Cu catalyzed Sonogashira coupling reaction between phenylacetylene and 4-bromophthalic acid which was for the first time employed as start material,followed by dehydration of 4-phenylethynylphthalic acid.Compared with traditional synthetic routes,this method provides several advantages such as readily available raw materials,convenient manipulation and high yield.The products were characterized by IR,~1H NMR,^（13）C NMR,MS and elemental analysis,respectively.展开更多
Pd-Co films with the Co content varying from 21.9% to 34.62%（mole fraction） and Pd-Cu（5% Cu, mole fraction） film were electrodeposited on 316 L stainless steel, and the erosion-corrosion resistance of the Pd-Co an...Pd-Co films with the Co content varying from 21.9% to 34.62%（mole fraction） and Pd-Cu（5% Cu, mole fraction） film were electrodeposited on 316 L stainless steel, and the erosion-corrosion resistance of the Pd-Co and Pd-Cu plated samples in a simulated boiling pure terephthalic acid（PTA） slurry environment was studied with methods of mass loss test, polarization measurement and scanning electron microscopy（SEM）. Under the static state condition, both the Pd-Cu and Pd-Co plated samples exhibit good corrosion resistance and the Pd-Cu film behaves slightly better. However, with increasing the stirring speed, the corrosion rate of the Pd-Cu plated samples increases obviously while that of the Pd-Co plated samples shows only slight increase. Higher microhardness and lower surface roughness of Pd-Co film than those of Pd-Cu film, as well as good corrosion resistance, may be the main reasons for better erosion-corrosion resistance in the strong reductive acid plus erosion environment.展开更多
Main observation and conclusion A highly enantioselective 2,3-allenylation of acyclic and cyclicα-imino carboxylates via a synergistic bimetallic Pd/Cu catalysis with the same commercially available(R,Rp)-iPr-FOXAP(a...Main observation and conclusion A highly enantioselective 2,3-allenylation of acyclic and cyclicα-imino carboxylates via a synergistic bimetallic Pd/Cu catalysis with the same commercially available(R,Rp)-iPr-FOXAP(also as Phosferrox,(R,R)-[2-(4’-i-propyloxazolin-2’-yl)ferrocenyl]diphenyl phosphine)ligand for both metals affording optically active 2,3-butadienylα-amino acid derivatives in high to excellent yields with excellent enantioselectivities has been developed.展开更多
Anisotropic Pd nanoparticles with highly branched morphologies are urgently needed as building blocks for nanoscale devices, catalysts, and sensing materials owing to their novel structures and unique physicochemical ...Anisotropic Pd nanoparticles with highly branched morphologies are urgently needed as building blocks for nanoscale devices, catalysts, and sensing materials owing to their novel structures and unique physicochemical properties. However, realizing size control and branch manipulation for these materials is very challenging. In this study, we develop a facile ultrafine Cu seed-mediated approach in the aqueous phase to produce novel Pd-Cu trigonal hierarchical nanoframes （THNFs）. The main branch of most of the obtained nanocrystals is tripod-like, with advanced branches along the arms as frame units having self-similarity. In this method, the size of the Pd-Cu THNFs can be flexibly controlled by manipulating the nucleation involving the sub-3 nm Cu seeds. These Pd-Cu THNFs outperform Pd black with regard to their ethanol-oxidation performance, having a specific activity and mass activity 9.7 and 6.6 times higher, respectively. This research provides a versatile ultrafine seed-mediated approach for producing size-controlled anisotropic bimetallic nanoframes.展开更多
AstereodivergentPd/Cucatalyst systemforasymmetric desymmetric alkylation of allylic geminal dicarboxylates has been developed,which was successfully applied to the asymmetric synthesis of β-hydroxycarbonylmotifs bear...AstereodivergentPd/Cucatalyst systemforasymmetric desymmetric alkylation of allylic geminal dicarboxylates has been developed,which was successfully applied to the asymmetric synthesis of β-hydroxycarbonylmotifs bearing a versatile carbon-carbon double bond in an enantio-and diastereodivergent manner.A wide scope of substrates including challenging alkylsubstituted,2-substituted,and3,3′-disubstitutedallylic species are compatible with this catalytic system,delivering the substituted products in high to excellent yieldsandwith excellent diastereo-(upto>20:1 dr)and enantioselectivities(up to>99%ee).Furthermore,the mechanism of this dual Pd/Cu catalytic system including:(1)the desymmetrization process ofgeminal dicarboxylates;(2)the origin of regioselectivity(branched or linear);(3)the enantio-and diastereoselectivity observed by changing the combinations of two chiral metal catalysts,have been carefully investigated by theoretical calculations.展开更多
Nanoporous Pd and binary Pd-Cu particles were prepared by a hydrothermal method using ethylene glycol as a reduction agent and they were directly immobilized on Ti substrates named as Ti-supported Pd-based catalysts. ...Nanoporous Pd and binary Pd-Cu particles were prepared by a hydrothermal method using ethylene glycol as a reduction agent and they were directly immobilized on Ti substrates named as Ti-supported Pd-based catalysts. Their electrocatalytic activity for formic acid oxidation and oxygen reduction reaction （ORR） in alkaline media was examined by voltammetric techniques. Among the as-prepared catalysts, nanoPdslCu19/Ti catalyst presents the highest current density of 39.8 mA/cm2 at -0.5 V or 66.4 mA/cm2 at -0.3 V for formic acid oxidation. The onset potential of ORR on the nanoPdslCU19/Ti catalyst presents an about 70 mV positive shift compared to that on the nanoPd/Ti, and the current density of ORR at -0.3 V is 2.12 mA/cm2, which is 3.7 times larger than that on the nanoPd/Ti.展开更多
The presence of a limited amount of H2S in H2-rich feed adversely affects the Pd-Cu membrane permeation performance due to the sulphidization of the membrane surface. A theoretical model was proposed to predict the S-...The presence of a limited amount of H2S in H2-rich feed adversely affects the Pd-Cu membrane permeation performance due to the sulphidization of the membrane surface. A theoretical model was proposed to predict the S-tolerant performance of the Pd-Cu membranes in presence of H2S under the industrial water-gas-shift(WGS) reaction conditions. The ideas of surface coverage and competitive adsorption thermodynamics of H2S and H2 on Pd-Cu surface were introduced in the model. The surface sulphidization of the Pd-Cu membranes mainly depended on the pressure ratio of H2S to H2, temperature and S-adsorbed surface coverage, i.e., the occurrence of sulphidization on the surface was not directly related with the bulk compositions and structures [body centered cubic and face centered cubic(bcc or fcc)] of Pd-Cu alloy membranes because of the surface segregation phenomena. The resulting equilibrium equations for the H2S adsorption/sulphidization reactions were solved to calculate the pressure ratio of H2S to H2 over a wide range of temperatures. A validation of the model was performed through a comparison between lots of literature data and the model calculations over a rather broad range of operating conditions. An extremely good agreement was obtained in the different cases, and thus, the model can serve to guide the development of S-resistant Pd alloy membrane materials for hydrogen separation.展开更多
文摘A Pd-Cu catalyst, with primary B2-type phase, supported by VulcanXC-7R carbon was synthesized via a solvothermal method. The catalysts were physically and electrochemically characterized by X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS）, trans- mission electron microscopy （TEM） and both cyclic and linear sweep voltammetry using a rotating disk electrode （RDE）. During the RDE testing, the half-wave potential of the Pd-Cu/Vulcan catalyst was 50 mV higher compared to that of commercial Pt/C catalyst for the oxygen reduction reaction （ORR） in alkaline media. The Pd-Cu/Vulcan exhibited a specific activity of 1.27 mA/cm2 and a mass activity of 0.59 A/mgpd at 0.9 V, which were 4 and 3 times greater than that of the commercial Pt/C catalyst, respectively. The Pd-Cu/Vulcan catalyst also showed higher in-situ alkaline exchange membrane fuel cell （AEMFC） performance, with operating power densities of 1100 MW/cm2 operating on H2/O2 and 700 MW/cm2 operating on H2/Air （CO2-free）, which were markedly higher than those of the commercial Pt/C. The Pd-Cu/ Vulcan catalyst also exhibited high stability during a short-term, in-situ AEMFC durability test, with only around 11% performance loss after 30 hours of operation, an improve- ment over most AEMFCs reported in the literature to date.
基金This work was accomplished under the support of National Natural Science Foundation of Tianjin,China(No.22175127)Institute of Energy,Hefei Comprehensive National Science Center(No.19KZS207).
文摘Ultrathin Pd nanosheets(NSs)have great advantages in catalysis due to their large specific surface area and high percentage of under-coordinated atoms.However,the electrochemical performance still can be improved via composition-controllable growth of their solid solution.Herein,seeded alloying strategy was proposed to synthesize Pd-Cu solid solution from Pd NSs and Pd-Cu nanostructures with tunable molar ratios obtained by changing the amount of Cu precursor.As compared to the pristine Pd NSs,the Pd-Cu solid solution shows significantly enhanced methanol oxidation reaction(MOR)performance over those of Pd NSs and homemade Pd/C as the incorporation of Cu weakens the adsorption of CO intermediate on Pd in the MOR process.The choice of template is pivotal to the growth,as a shape-dependent behavior could be identified in the alloying of Cu with Pd nanosheets enclosed by{111}and{100}facets,Pd nanocubes enclosed by{100}facet,and Pd nano-tetrahedrons enclosed by{111}facet.The Pd-Cu solid solution with tunable composition can only be obtained from Pd NSs and the shape-dependent alloying process is mainly determined by the diffusion barrier and the minimum diffusion depth of the different facets.
基金This work was supported by grants from the National Natural Science Foundation of China(Nos.52070147 and 52270077)the Special Fund of the State Key Joint Laboratory of Environment Simulation and Pollution Control(No.22K06ESPCT)the Promotion Plan for Young Teachers’Scientific Research Ability of Minzu University of China(Nos.2021QNPY83 and 2022QNPY51).
文摘Excessive nitrate in water is harmful to the ecological environment and human health.Electrocatalytic reduction is a promising technology for nitrate removal.Herein,a Pd-Cu modified carbon nanotube membrane was fabricated with an electrodeposition method and used to reduce nitrate in a flowthrough electrochemical reactor.The optimal potential and duration for codeposition of Pd and Cu were-0.7 V and 5 min,respectively,according to linear scan voltammetry results.The membrane obtained with a Pd:Cu ratio of 1:1 exhibited a relatively high nitrate removal efficiency and N_(2)selectivity.Nitrate was almost completely reduced(~99%)by the membrane at potentials lower than-1.2 V.However,-0.8 V was the optimal potential for nitrate reduction in terms of both nitrate removal efficiency and product selectivity.The nitrate removal efficiency was 56.2%,and the N_(2)selectivity was 23.8%for the Pd:Cu=1:1 membrane operated at-0.8 V.Nitrate removal was enhanced under acidic conditions,while N_(2)selectivity was decreased.The concentrations of Cl-ions and dissolved oxygen showed little effect on nitrate reduction.The mass transfer rate constant was greatly improved by 6.6 times from 1.14×10^(-3)m/h at a membrane flux of 1 L/(m^(2)·h)to 8.71×10^(-3)m/h at a membrane flux of 15 L/(m^(2)·h),which resulted in a significant increase in the nitrate removal rate from 13.6 to 133.5 mg/(m^(2)·h).These findings show that the Pd-Cu modified CNT membrane is an efficient material for nitrate reduction.
基金the National Undergraduates' Innovative Experiment Project of China and the Undergraduates' Innovative Experiment Project of Sichuan University for financial support
文摘A novel approach to the synthesis of 4-phenylethynylphthalic anhydride has been described.The target compound was synthesized by Pd/Cu catalyzed Sonogashira coupling reaction between phenylacetylene and 4-bromophthalic acid which was for the first time employed as start material,followed by dehydration of 4-phenylethynylphthalic acid.Compared with traditional synthetic routes,this method provides several advantages such as readily available raw materials,convenient manipulation and high yield.The products were characterized by IR,~1H NMR,^（13）C NMR,MS and elemental analysis,respectively.
基金Project(2012BAE04B01) supported by the National Key Technology Research and Development Program of the Ministry of Science and Technology of China
文摘Pd-Co films with the Co content varying from 21.9% to 34.62%（mole fraction） and Pd-Cu（5% Cu, mole fraction） film were electrodeposited on 316 L stainless steel, and the erosion-corrosion resistance of the Pd-Co and Pd-Cu plated samples in a simulated boiling pure terephthalic acid（PTA） slurry environment was studied with methods of mass loss test, polarization measurement and scanning electron microscopy（SEM）. Under the static state condition, both the Pd-Cu and Pd-Co plated samples exhibit good corrosion resistance and the Pd-Cu film behaves slightly better. However, with increasing the stirring speed, the corrosion rate of the Pd-Cu plated samples increases obviously while that of the Pd-Co plated samples shows only slight increase. Higher microhardness and lower surface roughness of Pd-Co film than those of Pd-Cu film, as well as good corrosion resistance, may be the main reasons for better erosion-corrosion resistance in the strong reductive acid plus erosion environment.
基金Financial support from the National Natural Science Foundation of China(Grant No.21690063 to S.M.,and Grant No.21901158 to X.H.)is greatly appreciated.We thank Mr.Huanan Wang in this group for reproducing the results of(R)-3'd,(Rm-3and(R)-17k,presented in Tables 2,3,and 4,respectively.
文摘Main observation and conclusion A highly enantioselective 2,3-allenylation of acyclic and cyclicα-imino carboxylates via a synergistic bimetallic Pd/Cu catalysis with the same commercially available(R,Rp)-iPr-FOXAP(also as Phosferrox,(R,R)-[2-(4’-i-propyloxazolin-2’-yl)ferrocenyl]diphenyl phosphine)ligand for both metals affording optically active 2,3-butadienylα-amino acid derivatives in high to excellent yields with excellent enantioselectivities has been developed.
基金We acknowledge financial support from the National Basic Research Program of China （Nos. 2014CB845605 and 2013CB933200）, the National Natural Science Foundation of China （Nos. 21521061, 21573238, 21331006, 21571177, and 21520102001）, Strtegic Priority Research Program of the Chinese Academy of Sciences （No. XDB20000000）, the Natural Science Foundation of the Fujian Province （No. 2014J05022）, and the Chunmiao Project of the Haixi Institute of the Chinese Academy of Sciences （No. CMZX-2014-004）.
文摘Anisotropic Pd nanoparticles with highly branched morphologies are urgently needed as building blocks for nanoscale devices, catalysts, and sensing materials owing to their novel structures and unique physicochemical properties. However, realizing size control and branch manipulation for these materials is very challenging. In this study, we develop a facile ultrafine Cu seed-mediated approach in the aqueous phase to produce novel Pd-Cu trigonal hierarchical nanoframes （THNFs）. The main branch of most of the obtained nanocrystals is tripod-like, with advanced branches along the arms as frame units having self-similarity. In this method, the size of the Pd-Cu THNFs can be flexibly controlled by manipulating the nucleation involving the sub-3 nm Cu seeds. These Pd-Cu THNFs outperform Pd black with regard to their ethanol-oxidation performance, having a specific activity and mass activity 9.7 and 6.6 times higher, respectively. This research provides a versatile ultrafine seed-mediated approach for producing size-controlled anisotropic bimetallic nanoframes.
基金supported by the National Natural Science Foundation of China(nos.21620102003,21831005,21901158,and 21991112)the Shanghai Sailing Program(no.19YF1421900)+3 种基金Shanghai Municipal Education Commission(no.201701070002E00030)National Key R&D Program of China(no.2018YFE0126800)the Science and Technology Commission of Shanghai Municipality(no.19JC1430100)Zhiyuan Scholar Program(no.ZIRC2020-04).
文摘AstereodivergentPd/Cucatalyst systemforasymmetric desymmetric alkylation of allylic geminal dicarboxylates has been developed,which was successfully applied to the asymmetric synthesis of β-hydroxycarbonylmotifs bearing a versatile carbon-carbon double bond in an enantio-and diastereodivergent manner.A wide scope of substrates including challenging alkylsubstituted,2-substituted,and3,3′-disubstitutedallylic species are compatible with this catalytic system,delivering the substituted products in high to excellent yieldsandwith excellent diastereo-(upto>20:1 dr)and enantioselectivities(up to>99%ee).Furthermore,the mechanism of this dual Pd/Cu catalytic system including:(1)the desymmetrization process ofgeminal dicarboxylates;(2)the origin of regioselectivity(branched or linear);(3)the enantio-and diastereoselectivity observed by changing the combinations of two chiral metal catalysts,have been carefully investigated by theoretical calculations.
基金Project(10JJ9003) supported by Hunan Provincial Natural Science Foundation and Xiangtan Natural Science United Foundation,China Project(11K023) supported by Scientific Research Fund of Hunan Provincial Education Department,China
文摘Nanoporous Pd and binary Pd-Cu particles were prepared by a hydrothermal method using ethylene glycol as a reduction agent and they were directly immobilized on Ti substrates named as Ti-supported Pd-based catalysts. Their electrocatalytic activity for formic acid oxidation and oxygen reduction reaction （ORR） in alkaline media was examined by voltammetric techniques. Among the as-prepared catalysts, nanoPdslCu19/Ti catalyst presents the highest current density of 39.8 mA/cm2 at -0.5 V or 66.4 mA/cm2 at -0.3 V for formic acid oxidation. The onset potential of ORR on the nanoPdslCU19/Ti catalyst presents an about 70 mV positive shift compared to that on the nanoPd/Ti, and the current density of ORR at -0.3 V is 2.12 mA/cm2, which is 3.7 times larger than that on the nanoPd/Ti.
基金Supported by the National Natural Science Foundation of China(50972038)the National Natural Science Foundation of Hebei Province(B2009000739,B2014209258)Science and Technology Support Program of Hebei Province(09215142D)
文摘The presence of a limited amount of H2S in H2-rich feed adversely affects the Pd-Cu membrane permeation performance due to the sulphidization of the membrane surface. A theoretical model was proposed to predict the S-tolerant performance of the Pd-Cu membranes in presence of H2S under the industrial water-gas-shift(WGS) reaction conditions. The ideas of surface coverage and competitive adsorption thermodynamics of H2S and H2 on Pd-Cu surface were introduced in the model. The surface sulphidization of the Pd-Cu membranes mainly depended on the pressure ratio of H2S to H2, temperature and S-adsorbed surface coverage, i.e., the occurrence of sulphidization on the surface was not directly related with the bulk compositions and structures [body centered cubic and face centered cubic(bcc or fcc)] of Pd-Cu alloy membranes because of the surface segregation phenomena. The resulting equilibrium equations for the H2S adsorption/sulphidization reactions were solved to calculate the pressure ratio of H2S to H2 over a wide range of temperatures. A validation of the model was performed through a comparison between lots of literature data and the model calculations over a rather broad range of operating conditions. An extremely good agreement was obtained in the different cases, and thus, the model can serve to guide the development of S-resistant Pd alloy membrane materials for hydrogen separation.
