It is reported for the first time that the Pt/C catalyst can be prepared with a new and simple organic sol method using SnCl2 as the reductant. It was found that the average size of the Pt particles in the Pt/C cataly...It is reported for the first time that the Pt/C catalyst can be prepared with a new and simple organic sol method using SnCl2 as the reductant. It was found that the average size of the Pt particles in the Pt/C catalysts could be controlled with controlling the preparation conditions. The effect of the average sizes of the Pt particles in the Pt/C catalysts obtained with this method on the electrocatalytical activity of the oxidation of methanol was investigated.展开更多
A series of Pt/C catalysts for proton exchange membrane fuel cells(PEMFCs) with various metal loadings is synthesized by a microwave-assisted polyol process via mixing an extremely stable platinum colloid(> 3 month...A series of Pt/C catalysts for proton exchange membrane fuel cells(PEMFCs) with various metal loadings is synthesized by a microwave-assisted polyol process via mixing an extremely stable platinum colloid(> 3 months’ shelf life) from single batch preparation with activated carbon ethylene glycol suspension.21 wt%, 42 wt% and 61 wt% Pt loadings are employed to showcase the advantages of the improved polyol process. The ultraviolet(UV)–visible spectra and ζ-potential measurements are conducted to monitor the wet chemistry process during catalyst preparation. The powder X-ray diffraction(XRD), transmission electron microscopy(TEM) and thermogravimetric analysis(TGA) characterizations are carried out on catalysts. The catalyst activities are investigated using electrochemical and single cell tests. The stability of Pt nanoparticle colloid is explored by ORR, cyclic voltammetry(CV) and ζ-potential measurements. The TEM results show the Pt particle sizes of the colloid, and the sizes of the 21 wt%, 42 wt% and 61 wt%Pt/C samples are 2.1–3.9 nm. Because of the high Pt dispersion, the Pt/C catalysts exhibit superior electroactivity toward ORR. In addition, four 61 wt% Pt/C catalysts made from the Pt colloid with 0–3 months’ shelf life show almost the same performance, which exhibits superior stability of the Pt colloid system without surfactant protection.展开更多
Taming the electron transfer across metal–support interfaces appears to be an attractive yet challenging methodology to boost catalytic properties.Herein,we demonstrate a precise engineering strategy for the carbon s...Taming the electron transfer across metal–support interfaces appears to be an attractive yet challenging methodology to boost catalytic properties.Herein,we demonstrate a precise engineering strategy for the carbon surface chemistry of Pt/C catalysts—that is,for the electron-withdrawing/donating oxygencontaining groups on the carbon surface—to fine-tune the electrons of the supported metal nanoparticles.Taking the ammonia borane hydrolysis as an example,a combination of density functional theory(DFT)calculations,advanced characterizations,and kinetics and isotopic analyses reveals quantifiable relationships among the carbon surface chemistry,Pt charge state and binding energy,activation entropy/enthalpy,and resultant catalytic activity.After decoupling the influences of other factors,the Pt charge is unprecedentedly identified as an experimentally measurable descriptor of the Pt active site,contributing to a 15-fold increment in the hydrogen generation rate.Further incorporating the Pt charge with the number of Pt active sites,a mesokinetics model is proposed for the first time that can individually quantify the contributions of the electronic and geometric properties to precisely predict the catalytic performance.Our results demonstrate a potentially groundbreaking methodology to design and manipulate metal–carbon catalysts with desirable properties.展开更多
Tuning Strong Metal-support Interactions(SMSI)is a key strategy to obtain highly active catalysts,but conventional methods usually enable TiO_(x) encapsulation of noble metal components to minimize the exposure of nob...Tuning Strong Metal-support Interactions(SMSI)is a key strategy to obtain highly active catalysts,but conventional methods usually enable TiO_(x) encapsulation of noble metal components to minimize the exposure of noble metals.This study demonstrates a catalyst preparation method to modulate a weak encapsulation of Pt metal nanoparticles(NPs)with the supported TiO_(2),achieving the moderate suppression of SMSI effects.The introduction of silica inhibits this encapsulation,as reflected in the characterization results such as XPS and HRTEM,while the Ti^(4+) to Ti^(3+) conversion due to SMSI can still be found on the support surface.Furthermore,the hydrogenation of cinnamaldehyde(CAL)as a probe reaction revealed that once this encapsulation behavior was suppressed,the adsorption capacity of the catalyst for small molecules like H_(2) and CO was enhanced,which thereby improved the catalytic activity and facilitated the hydrogenation of CAL.Meanwhile,the introduction of SiO_(2) also changed the surface structure of the catalyst,which inhibited the occurrence of the acetal reaction and improved the conversion efficiency of C=O and C=C hydrogenation.Systematic manipulation of SMSI formation and its consequence on the performance in catalytic hydrogenation reactions are discussed.展开更多
High-purity of hydrogen is vital to the guarantee of end usage in proton exchange membrane fuel cell(PEMFC)electric vehicles(EVs)with superior durability and low expense.However,the currently employed hydrogen,primari...High-purity of hydrogen is vital to the guarantee of end usage in proton exchange membrane fuel cell(PEMFC)electric vehicles(EVs)with superior durability and low expense.However,the currently employed hydrogen,primarily from fossil fuel,still contains some poisoning impurities that significantly affect the durability of PEMFCs.Here,we investigate the poisoning effect of several typical hydrogen impurities(S^(2-),Cl^(-),HCOO^(-)and CO_(3)^(2-))on the hydrogen oxidation reaction(HOR)of the state-of-the-art carbon-supported platinum(Pt/C)catalyst used in the PEMFC anode.Electrochemical results indicate that the electrochemically active surface area of Pt/C is hampered by these hydrogen impurities with reduced effective Pt reactive sites due to the competitive adsorption against hydrogen at Pt sites showing the extent of the poisoning on Pt sites in the order:S^(2-)>Cl^(-)>HCOO^(-)>CO_(3)^(2-).Density functional theory calculations reveal that the adsorption energy of S2-on Pt(111)is greater than that of Cl^(-),HCOO^(-)and CO_(2),and the electronic structure of Pt is found to be changed due to the adsorption of impurities showing the downshift of the d-band centre of Pt that weakens the adsorption of hydrogen on the Pt sites.This work provides valuable guidance for future optimization of hydrogen quality and also emphasizes the importance of anti-poisoning anode catalyst development,especially towards H_(2)S impurities that seriously affect the durability of PEMFCs.展开更多
Platinum nanoparticles supported on carbons（Pt/C,60%,mass fraction） electrocatalysts for direct methanol fuel cell（DMFC） were prepared by citrate-stabilized method with different reductants and carbon supports.The...Platinum nanoparticles supported on carbons（Pt/C,60%,mass fraction） electrocatalysts for direct methanol fuel cell（DMFC） were prepared by citrate-stabilized method with different reductants and carbon supports.The catalysts were characterized by X-ray diffraction（XRD）,transmission electron microscopy（TEM） and cyclic voltammetry（CV）.It is found that the size of Pt nanoparticles on carbon is controllable by citrate addition and reductant optimization,and the form of carbon support has a great influence on electrocatalytic activity of catalysts.The citrate-stabilized Pt nanoparticles supported on BP2000 carbon,which was reduced by formaldehyde,exhibit the best performance with about 2 nm in diameter and 66.46 m2/g（Pt） in electrocatalytic active surface（EAS） area.Test on single DMFC with 60%（mass fraction） Pt/BP2000 as cathode electrocatalyst showed maximum power density at 78.8 mW/cm2.展开更多
The structure and catalytic properties of PtSn catalysts supported on SUZ-4 and ZSM-5 zeolite have been studied by using various experimental techniques including XRD,nitrogen adsorption,NH3-TPD,TG,H2-TPR and TPO tech...The structure and catalytic properties of PtSn catalysts supported on SUZ-4 and ZSM-5 zeolite have been studied by using various experimental techniques including XRD,nitrogen adsorption,NH3-TPD,TG,H2-TPR and TPO techniques combined with propane dehydrogenation tests.It has been shown that SUZ-4-supported PtSnNa（PtSnNa/SUZ-4） was determined to be a better catalyst for propane dehydrogenation than conventional catalysts supported on ZSM-5,owing to its higher catalytic activity and stability.Dibenzothiophene poisoning experiments were performed to investigate the detailed structures of the two supported catalysts.The characterization of the two catalysts indicates that the distribution of Pt on the porous support affects the activity.In contrast to ZSM-5-supported catalysts,Pt particles on the PtSnNa/SUZ-4 are primarily dispersed over the external surface and are not as readily deactivated by carbon deposition.This is because that the strong acid sites of the SUZ-4 zeolite evidently prevented the impregnation of the Pt precursor H_2PtCl_6 into the zeolite.In contrast,the weak acid sites of the ZSM-5 zeolite led to more of the precursor entering the zeolite tunnels,followed by transformation to highly dispersed Pt clusters during calcination.In the case of the PtSnNa/ZSM-5,the interactions between Sn oxides and the support were lessened,owing to the weaker acidity of the ZSM-5 zeolite.The dispersed Sn oxides were therefore easier to reduce to the metallic state,thus decreasing the catalytic activity for hydrocarbon dehydrogenation.展开更多
Platinum/cerium-zirconium-sulfate（Pt/Ce-Zr-SO_4^（2-）） catalysts were prepared by wetness impregnation.Catalytic activities were evaluated from the combustion of propene and CO.Sulfate（SO_4^（2-））addition improv...Platinum/cerium-zirconium-sulfate（Pt/Ce-Zr-SO_4^（2-）） catalysts were prepared by wetness impregnation.Catalytic activities were evaluated from the combustion of propene and CO.Sulfate（SO_4^（2-））addition improved the catalytic activity significantly.When using Pt/Ce-Zr-SO_4^（2-） with 10 wt%SO_4^（2-）,the temperature for 90%conversion of propene and CO decreased by 75℃ compared with Pt/Ce-Zr.The conversion exceeded 95%at 240℃ even after 0.02%sulfur dioxide poisoning for 20 h.Temperature-programmed desorption of CO and X-ray photoelectron spectroscopy analyses revealed an improvement in Pt dispersion onto the Ce-Zr-SO_4^（2-） support,and the increased number of Pt particles built up more Pt^（-）-（SO_4^（2-））^（-） couples,which resulted in excellent activity.The increased total acidity and new Bronsted acid sites on the surface provided the Pt/Ce-Zr-SO_4^（2-） with good sulfur resistance.展开更多
A variety of spherical and structured activated charcoal supported Pt/Fe3O4 composites with an average particle size of ~100 nm have been synthesized by a self-assembly method using the difference of reduction potenti...A variety of spherical and structured activated charcoal supported Pt/Fe3O4 composites with an average particle size of ~100 nm have been synthesized by a self-assembly method using the difference of reduction potential between Pt （Ⅳ） and Fe （Ⅱ） precursors as driving force. The formed Fe3O4 nanoparticles （NPs） effectively prevent the aggregation of Pt nanocrystallites and promote the dispersion of Pt NPs on the surface of catalyst, which will be favorable for the exposure of Pt active sites for high-efficient adsorption and contact of substrate and hydrogen donor. The electron-enrichment state of Pt NPs donated by Fe304 nanocrystallites is corroborated by XPS measurement, which is responsible for promoting and activating the terminal C=O bond of adsorbed substrate via a vertical configuration. The experimental results show that the activated charcoal supported Pt/Fe3O4 catalyst exhibits 94.8% selectivity towards cinnamyl alcohol by the transfer hydrogenation of einnamaldehyde with Pt loading of 2.46% under the optimum conditions of 120 ℃ for 6 h, and 2-propanol as a hydrogen donor. Additionally, the present study demonstrates that a high-efficient and recyclable catalyst can be rapidly separated from the mixture due to its natural magnetism upon the application of magnetic field.展开更多
文摘It is reported for the first time that the Pt/C catalyst can be prepared with a new and simple organic sol method using SnCl2 as the reductant. It was found that the average size of the Pt particles in the Pt/C catalysts could be controlled with controlling the preparation conditions. The effect of the average sizes of the Pt particles in the Pt/C catalysts obtained with this method on the electrocatalytical activity of the oxidation of methanol was investigated.
基金financial supports from National Key R&D Plan of China (2017YFB0102803)the National Natural Science Foundation of China (21676135)+8 种基金Scientific Instrument Develop Major Project of National Natural Science Foundation of China (51627810)Joint Funds of the National Natural Science Foundation and Liaoning of China (U1508202)Key R&D programs in Jiangsu (BE2018051)“333” project of Jiangsu Province (BRA2018007)Natural Science Foundation of Jiangsu Province (BK20161273, BK20181199)the Graduate Innovation Foundation of Nanjing university (2017ZDL05)support of PAPD of Jiangsu Higher Education Institutions“Six Talent Peaks Program” of Jiangsu ProvinceFundamental Research Funds for the Central Universities, China。
文摘A series of Pt/C catalysts for proton exchange membrane fuel cells(PEMFCs) with various metal loadings is synthesized by a microwave-assisted polyol process via mixing an extremely stable platinum colloid(> 3 months’ shelf life) from single batch preparation with activated carbon ethylene glycol suspension.21 wt%, 42 wt% and 61 wt% Pt loadings are employed to showcase the advantages of the improved polyol process. The ultraviolet(UV)–visible spectra and ζ-potential measurements are conducted to monitor the wet chemistry process during catalyst preparation. The powder X-ray diffraction(XRD), transmission electron microscopy(TEM) and thermogravimetric analysis(TGA) characterizations are carried out on catalysts. The catalyst activities are investigated using electrochemical and single cell tests. The stability of Pt nanoparticle colloid is explored by ORR, cyclic voltammetry(CV) and ζ-potential measurements. The TEM results show the Pt particle sizes of the colloid, and the sizes of the 21 wt%, 42 wt% and 61 wt%Pt/C samples are 2.1–3.9 nm. Because of the high Pt dispersion, the Pt/C catalysts exhibit superior electroactivity toward ORR. In addition, four 61 wt% Pt/C catalysts made from the Pt colloid with 0–3 months’ shelf life show almost the same performance, which exhibits superior stability of the Pt colloid system without surfactant protection.
基金the Natural Science Foundation of China(21922803,92034301,22008066,and 21776077)the China Postdoctoral Science Foundation(BX20190116)+1 种基金the Innovation Program of Shanghai Municipal Education Commission,the Program of Shanghai Academic/Tech-nology Research Leader(21XD1421000)111 Project of the Min-istry of Education of China(B08021)。
文摘Taming the electron transfer across metal–support interfaces appears to be an attractive yet challenging methodology to boost catalytic properties.Herein,we demonstrate a precise engineering strategy for the carbon surface chemistry of Pt/C catalysts—that is,for the electron-withdrawing/donating oxygencontaining groups on the carbon surface—to fine-tune the electrons of the supported metal nanoparticles.Taking the ammonia borane hydrolysis as an example,a combination of density functional theory(DFT)calculations,advanced characterizations,and kinetics and isotopic analyses reveals quantifiable relationships among the carbon surface chemistry,Pt charge state and binding energy,activation entropy/enthalpy,and resultant catalytic activity.After decoupling the influences of other factors,the Pt charge is unprecedentedly identified as an experimentally measurable descriptor of the Pt active site,contributing to a 15-fold increment in the hydrogen generation rate.Further incorporating the Pt charge with the number of Pt active sites,a mesokinetics model is proposed for the first time that can individually quantify the contributions of the electronic and geometric properties to precisely predict the catalytic performance.Our results demonstrate a potentially groundbreaking methodology to design and manipulate metal–carbon catalysts with desirable properties.
基金the National Natural Science Foundation of China(21576291,22003076)National Natural Science Foundation of China-Outstanding Youth foundation(22322814)the Fundamental Research Funds for the Central Universities(23CX03007A,22CX06012A)are gratefully acknowledge。
文摘Tuning Strong Metal-support Interactions(SMSI)is a key strategy to obtain highly active catalysts,but conventional methods usually enable TiO_(x) encapsulation of noble metal components to minimize the exposure of noble metals.This study demonstrates a catalyst preparation method to modulate a weak encapsulation of Pt metal nanoparticles(NPs)with the supported TiO_(2),achieving the moderate suppression of SMSI effects.The introduction of silica inhibits this encapsulation,as reflected in the characterization results such as XPS and HRTEM,while the Ti^(4+) to Ti^(3+) conversion due to SMSI can still be found on the support surface.Furthermore,the hydrogenation of cinnamaldehyde(CAL)as a probe reaction revealed that once this encapsulation behavior was suppressed,the adsorption capacity of the catalyst for small molecules like H_(2) and CO was enhanced,which thereby improved the catalytic activity and facilitated the hydrogenation of CAL.Meanwhile,the introduction of SiO_(2) also changed the surface structure of the catalyst,which inhibited the occurrence of the acetal reaction and improved the conversion efficiency of C=O and C=C hydrogenation.Systematic manipulation of SMSI formation and its consequence on the performance in catalytic hydrogenation reactions are discussed.
基金supported by the National Key R&D Program of China (No.2019YFB1505004).
文摘High-purity of hydrogen is vital to the guarantee of end usage in proton exchange membrane fuel cell(PEMFC)electric vehicles(EVs)with superior durability and low expense.However,the currently employed hydrogen,primarily from fossil fuel,still contains some poisoning impurities that significantly affect the durability of PEMFCs.Here,we investigate the poisoning effect of several typical hydrogen impurities(S^(2-),Cl^(-),HCOO^(-)and CO_(3)^(2-))on the hydrogen oxidation reaction(HOR)of the state-of-the-art carbon-supported platinum(Pt/C)catalyst used in the PEMFC anode.Electrochemical results indicate that the electrochemically active surface area of Pt/C is hampered by these hydrogen impurities with reduced effective Pt reactive sites due to the competitive adsorption against hydrogen at Pt sites showing the extent of the poisoning on Pt sites in the order:S^(2-)>Cl^(-)>HCOO^(-)>CO_(3)^(2-).Density functional theory calculations reveal that the adsorption energy of S2-on Pt(111)is greater than that of Cl^(-),HCOO^(-)and CO_(2),and the electronic structure of Pt is found to be changed due to the adsorption of impurities showing the downshift of the d-band centre of Pt that weakens the adsorption of hydrogen on the Pt sites.This work provides valuable guidance for future optimization of hydrogen quality and also emphasizes the importance of anti-poisoning anode catalyst development,especially towards H_(2)S impurities that seriously affect the durability of PEMFCs.
基金Project(50573041)supported by the National Natural Science Foundation of China
文摘Platinum nanoparticles supported on carbons（Pt/C,60%,mass fraction） electrocatalysts for direct methanol fuel cell（DMFC） were prepared by citrate-stabilized method with different reductants and carbon supports.The catalysts were characterized by X-ray diffraction（XRD）,transmission electron microscopy（TEM） and cyclic voltammetry（CV）.It is found that the size of Pt nanoparticles on carbon is controllable by citrate addition and reductant optimization,and the form of carbon support has a great influence on electrocatalytic activity of catalysts.The citrate-stabilized Pt nanoparticles supported on BP2000 carbon,which was reduced by formaldehyde,exhibit the best performance with about 2 nm in diameter and 66.46 m2/g（Pt） in electrocatalytic active surface（EAS） area.Test on single DMFC with 60%（mass fraction） Pt/BP2000 as cathode electrocatalyst showed maximum power density at 78.8 mW/cm2.
基金supported by the Jiangsu Planned Projects for Postdoctoral Research Funds(1301080C)NNSFC(21202141,21173182)+1 种基金Key Science&Technology Specific Projects of Yangzhou(YZ20122029)the Innovation Foundation of Yangzhou University(2015CXJ009)~~
文摘The structure and catalytic properties of PtSn catalysts supported on SUZ-4 and ZSM-5 zeolite have been studied by using various experimental techniques including XRD,nitrogen adsorption,NH3-TPD,TG,H2-TPR and TPO techniques combined with propane dehydrogenation tests.It has been shown that SUZ-4-supported PtSnNa（PtSnNa/SUZ-4） was determined to be a better catalyst for propane dehydrogenation than conventional catalysts supported on ZSM-5,owing to its higher catalytic activity and stability.Dibenzothiophene poisoning experiments were performed to investigate the detailed structures of the two supported catalysts.The characterization of the two catalysts indicates that the distribution of Pt on the porous support affects the activity.In contrast to ZSM-5-supported catalysts,Pt particles on the PtSnNa/SUZ-4 are primarily dispersed over the external surface and are not as readily deactivated by carbon deposition.This is because that the strong acid sites of the SUZ-4 zeolite evidently prevented the impregnation of the Pt precursor H_2PtCl_6 into the zeolite.In contrast,the weak acid sites of the ZSM-5 zeolite led to more of the precursor entering the zeolite tunnels,followed by transformation to highly dispersed Pt clusters during calcination.In the case of the PtSnNa/ZSM-5,the interactions between Sn oxides and the support were lessened,owing to the weaker acidity of the ZSM-5 zeolite.The dispersed Sn oxides were therefore easier to reduce to the metallic state,thus decreasing the catalytic activity for hydrocarbon dehydrogenation.
基金supported by the National Natural Science Foundation of China(21506194,21676255)the Provincial Natural Science Foundation of Zhejiang Province(LY16B070011)the Commission of Science and Technology of Zhejiang Province(2017C33106,2017C03007)~~
文摘Platinum/cerium-zirconium-sulfate（Pt/Ce-Zr-SO_4^（2-）） catalysts were prepared by wetness impregnation.Catalytic activities were evaluated from the combustion of propene and CO.Sulfate（SO_4^（2-））addition improved the catalytic activity significantly.When using Pt/Ce-Zr-SO_4^（2-） with 10 wt%SO_4^（2-）,the temperature for 90%conversion of propene and CO decreased by 75℃ compared with Pt/Ce-Zr.The conversion exceeded 95%at 240℃ even after 0.02%sulfur dioxide poisoning for 20 h.Temperature-programmed desorption of CO and X-ray photoelectron spectroscopy analyses revealed an improvement in Pt dispersion onto the Ce-Zr-SO_4^（2-） support,and the increased number of Pt particles built up more Pt^（-）-（SO_4^（2-））^（-） couples,which resulted in excellent activity.The increased total acidity and new Bronsted acid sites on the surface provided the Pt/Ce-Zr-SO_4^（2-） with good sulfur resistance.
基金This work is supported by the National Natural Science Foundation of China （No.51372248, No.51432009 and No.51502297）, Instrument Developing Project of the Chinese Academy of Sciences （No.yz201421）, the CAS/SAFEA International Partnership Program for Creative Research Teams of Chinese Academy of Sciences, China.
文摘A variety of spherical and structured activated charcoal supported Pt/Fe3O4 composites with an average particle size of ~100 nm have been synthesized by a self-assembly method using the difference of reduction potential between Pt （Ⅳ） and Fe （Ⅱ） precursors as driving force. The formed Fe3O4 nanoparticles （NPs） effectively prevent the aggregation of Pt nanocrystallites and promote the dispersion of Pt NPs on the surface of catalyst, which will be favorable for the exposure of Pt active sites for high-efficient adsorption and contact of substrate and hydrogen donor. The electron-enrichment state of Pt NPs donated by Fe304 nanocrystallites is corroborated by XPS measurement, which is responsible for promoting and activating the terminal C=O bond of adsorbed substrate via a vertical configuration. The experimental results show that the activated charcoal supported Pt/Fe3O4 catalyst exhibits 94.8% selectivity towards cinnamyl alcohol by the transfer hydrogenation of einnamaldehyde with Pt loading of 2.46% under the optimum conditions of 120 ℃ for 6 h, and 2-propanol as a hydrogen donor. Additionally, the present study demonstrates that a high-efficient and recyclable catalyst can be rapidly separated from the mixture due to its natural magnetism upon the application of magnetic field.
