As one of the most important catalysts in polyethylene industry,Phillips catalyst(CrO_x/SiO_2)was quite unique for its activation by ethylene monomer without using any activator like alkyl-aluminium or MAO.In this wor...As one of the most important catalysts in polyethylene industry,Phillips catalyst(CrO_x/SiO_2)was quite unique for its activation by ethylene monomer without using any activator like alkyl-aluminium or MAO.In this work,the density functional theory(DFT)calculation combined with paired interacting orbitals(PIO)method was applied for the theoretical studies on coordination reaction mechanism between ethylene monomer and two model catalysts namely Cr(Ⅱ)(OH)_2(M1) and silsesquioxane-supported Cr(Ⅱ)(M2)as surfac...展开更多
Transition-metal based M-N_4/C catalysts are appealing for electrocatalytic oxygen reduction reaction(ORR) and oxygen evolution reaction(OER). Employing model catalysts, which have well-defined molecular structures an...Transition-metal based M-N_4/C catalysts are appealing for electrocatalytic oxygen reduction reaction(ORR) and oxygen evolution reaction(OER). Employing model catalysts, which have well-defined molecular structures and coordination environments, to investigate electrocatalytic performance of M-N_4/C sites for ORR and OER is of fundamental significance. Herein, we reported the use of Co tetra(phenyl)porphyrin 1 and Co tetra(pentafluorophenyl)porphyrin 2 as models to probe the role of Co-N_4/C sites for oxygen electrocatalysis. We showed that Co porphyrin 1 is more efficient than its structural analogue 2 for oxygen electrocatalysis in alkaline aqueous solutions, indicating that the electronrich Co-N_4/C site is more favored when noncovalently adsorbed on carbon supports. This work inspires rational design of reaction-oriented catalysts for sustainable energy storage and conversion technologies.展开更多
Selective catalytic reduction of NO by CO is challenging in environmental catalysis but attractive owing to the advantage of simultaneous elimination of NO and CO.Here,model catalysts consisting of Pd nanoparticles(NP...Selective catalytic reduction of NO by CO is challenging in environmental catalysis but attractive owing to the advantage of simultaneous elimination of NO and CO.Here,model catalysts consisting of Pd nanoparticles(NPs)and single-atom Pd supported on a CeO_(2)(111)film grown on Cu(111)(denoted as Pd NPs/CeO_(2)and Pd_(1)/CeO_(2),respectively)were successfully prepared and characterized by synchrotron radiation photoemission spectroscopy(SRPES)and infrared reflection absorption spectroscopy(IRAS).The NO+CO adsorption/reaction on the Pd_(1)/CeO_(2)and Pd NPs/CeO_(2)catalysts were carefully investigated using SRPES,temperature-programmed desorption(TPD),and IRAS.It is found that the reaction products on both model catalysts are in good agreement with those on real catalysts,demonstrating the good reliability of using these model catalysts to study the reaction mechanism of the NO+CO reaction.On the Pd NPs/CeO_(2)surface,N_(2)is formed by the combination of atomic N coming from the dissociation of NO on Pd NPs at higher temperatures.N_(2)O formation occurs probably via chemisorbed NO combined with atomic N on the surface.While on the single-atom Pd_(1)/CeO_(2)surface,no N_(2)O is detected.The 100%N_(2)selectivity may stem from the formation of O-N-N-O^(*)intermediate on the surface.Through this study,direct experimental evidence for the reaction mechanisms of the NO+CO reaction is provided,which supports the previous density functional theory(DFT)calculations.展开更多
Metal-free carbon,as the most representative heterogeneous metal-free catalysts,have received considerable interests in electro-and thermo-catalytic reac-tions due to their impressive performance and sustainability.Ov...Metal-free carbon,as the most representative heterogeneous metal-free catalysts,have received considerable interests in electro-and thermo-catalytic reac-tions due to their impressive performance and sustainability.Over the past decade,well-designed carbon catalysts with tunable structures and heteroatom groups coupled with various characterization techniques have proposed numerous reaction mechanisms.However,active sites,key intermediate species,precise structure-activity relationships and dynamic evolution processes of carbon catalysts are still rife with controversies due to the monotony and limitation of used experimental methods.In this Review,we sum-marize the extensive efforts on model catalysts since the 2000s,particularly in the past decade,to overcome the influences of material and structure limitations in metal-free carbon catalysis.Using both nanomolecule model and bulk model,the real contribution of each alien species,defect and edge configuration to a series of fundamentally important reactions,such as thermocatalytic reactions,electrocatalytic reactions,were systematically studied.Combined with in situ techniques,isotope labeling and size control,the detailed reaction mechanisms,the precise 2D structure-activity relationships and the rate-determining steps were revealed at a molecular level.Furthermore,the outlook of model carbon catalysis has also been proposed in this work.展开更多
Comprehensive Summary Recent progress in colloidal synthesis has realized the preparations of uniform nanocrystal(NC)model catalysts with rich and well-controlled morphologies that were employed to explore structure-a...Comprehensive Summary Recent progress in colloidal synthesis has realized the preparations of uniform nanocrystal(NC)model catalysts with rich and well-controlled morphologies that were employed to explore structure-activity relationships of powder catalysts,similar to single-crystal-based model catalysts under ultrahigh vacuum conditions but can work at the same conditions as powder catalysts without the"materials gap"and"pressure gap".In this perspective,the CeO_(2)-based NC model catalysts with various morphologies are included and their relevant progresses are critically reviewed.The detailed descriptions of morphology-controlled synthesis and characterizations of uniform CeO_(2)NCs.展开更多
An in-depth understanding of the structure-activity relationship between the surface structure,chemical composition,adsorption and desorption of molecules,and their reaction activity and selectivity is necessary for t...An in-depth understanding of the structure-activity relationship between the surface structure,chemical composition,adsorption and desorption of molecules,and their reaction activity and selectivity is necessary for the rational design of high-performance catalysts.Herein,we present a method for studying catalytic mechanisms using a combination of in situ reaction cells and surface science techniques.The proposed system consists of four parts:preparation chamber,temperatureprogrammed desorption(TPD)chamber,quick load-lock chamber,and in situ reaction cell.The preparation chamber was equipped with setups based on the surface science techniques used for standard sample preparation and characterization,including an Ar+sputter gun,Auger electron spectrometer,and a low-energy electron diffractometer.After a well-defined model catalyst was prepared,the sample was transferred to a TPD chamber to investigate the adsorption and desorption of the probe molecule,or to the reaction cell,to measure the catalytic activity.A thermal desorption experiment for methanol on a clean Cu(111)surface was conducted to demonstrate the functionality of the preparation and TPD chambers.Moreover,the repeatability of the in situ reaction cell experiment was verified by CO_(2) hydrogenation on the Ni(110)surface.At a reaction pressure of 800 Torr at 673 K,turnover frequencies for the methanation reaction and reverse water-gas shift reaction were 0.15 and 7.55 Ni atom^(-1) s^(-1),respectively.展开更多
CO oxidation has been performed on Co_(3)O_(4) nanobelts and nanocubes as model catalysts.The Co_(3)O_(4) nanobelts which have a predominance of exposed{011}planes are more active than Co_(3)O_(4) nanocubes with expos...CO oxidation has been performed on Co_(3)O_(4) nanobelts and nanocubes as model catalysts.The Co_(3)O_(4) nanobelts which have a predominance of exposed{011}planes are more active than Co_(3)O_(4) nanocubes with exposed{001}planes.Temperature programmed reduction of CO shows that Co_(3)O_(4) nanobelts have stronger reducing properties than Co_(3)O_(4) nanocubes.The essence of shape and crystal plane effect is revealed by the fact that turnover frequency of Co3+sites of{011}planes on Co_(3)O_(4) nanobelts is far higher than that of{001}planes on Co_(3)O_(4) nanocubes.展开更多
Understanding the atomic and electronic changes of active sites promotes the whole new sight into electrochemical carbon dioxide reduction reaction(CO_(2)RR),which provides a feasible strategy to achieve carbon neutra...Understanding the atomic and electronic changes of active sites promotes the whole new sight into electrochemical carbon dioxide reduction reaction(CO_(2)RR),which provides a feasible strategy to achieve carbon neutrality.Here we employ operando high-energy resolution fluorescence-detected Xray absorption spectroscopy(HERFD-XAS)to track the structural evolution of Ni(II)phthalocyanine(NiPc),considered as the model catalysts with uniform Ni-N_(4)-C_(8) moiety,during the CO_(2)RR.The HERFD-XAS method is in favor of elucidating the interaction of the reactant/catalyst interface from the atomic electronic structure dimension,facilitating the establishment of the catalytic mechanism and the dynamic structure changes.Based on operando measurement,surface sensitive difference spectra(△μ)and spectroscopy simulation,the interfacial interactions between the active sites of NiPc and reactants are monitored and the Ni species gradually reduced by increasing the applied potential is discovered.HERFD-XAS method offers an advanced and powerful tool for elucidating the complex catalytic mechanism in further various systems.展开更多
A solvothermal method was used to synthesize MIL-101(Fe)and MIL-88(Fe),which were used for alkylation of benzene.The synthesized catalysts were characterized by X-ray diffraction,Fourier transform infrared spectroscop...A solvothermal method was used to synthesize MIL-101(Fe)and MIL-88(Fe),which were used for alkylation of benzene.The synthesized catalysts were characterized by X-ray diffraction,Fourier transform infrared spectroscopy,field emission scanning electron microscope,dynamic light scattering,and BET techniques.Metal-organic frameworks(MOFs)were modeled to investigate the catalytic performance and existence of mass transfer limitations.Calculated effectiveness factors revealed absence of internal a nd external mass transfer.Sensitivity analysis revealed best operating conditions over MIL-101 at 120℃ and 5 bar and over MIL-88 at 142℃ and 9 bar.展开更多
Inverse oxide/metal model systems are frequently used to investigate catalytic structure-function relationships at an atomic level.By means of a novel atomic layer deposition process,growth of single-site Fe_(1)O_(x) ...Inverse oxide/metal model systems are frequently used to investigate catalytic structure-function relationships at an atomic level.By means of a novel atomic layer deposition process,growth of single-site Fe_(1)O_(x) on a Pt(111)single crystal surface was achieved,as confirmed by scanning tunneling microscopy(STM).The redox properties of the catalyst were characterized by synchrotron radiation based ambient pressure X-ray photoelectron spectroscopy(AP-XPS).After calcination treatment at 373 K in 1 mbar O_(2).the chemical state of the catalyst was determined as Fe^(3+).Reduction in 1 mbar H_(2) at 373 K demonstrates a facile reduction to Fe2+and complete hydroxylation at significantly lower temperatures than what has been reported for iron oxide nanoparticles.At reaction conditions relevant for preferential oxidation of CO in H_(2)(PROX),the catalyst exhibits a Fe3+state(ferric hydroxide)at 298 K while re-oxidation of iron oxide clusters does not occur under the same condition.CO oxidation proceeds on the single-site Fei(OH)3 through a mechanism including the loss of hydroxyl groups in the temperature range of 373 to 473 K,but no reaction is observed on iron oxide clusters.The results highlight the high flexibility of the single iron atom catalyst in switching oxidation states,not observed for iron oxide nanoparticles under similar reaction conditions,which may indicate a higher intrinsic activity of such single interfacial sites than the conventional metal-oxide interfaces.In summary,our findings of the redox properties on inverse single-site iron oxide model catalyst may provide new insights into applied Fe-Pt catalysis.展开更多
Electronic adjustment is one of the most commonly used strategies to improve the catalytic performance of heterogeneous catalysts. We prepared hexagonal ultrathin Pd nanosheets with edges modified by gold nanoparticl...Electronic adjustment is one of the most commonly used strategies to improve the catalytic performance of heterogeneous catalysts. We prepared hexagonal ultrathin Pd nanosheets with edges modified by gold nanoparticles (Au@Pd nanosheets) using galvanic replacement method. By virtue of the electronic interactions between the Pd nanosheets and Au nanoparticles, the Au@Pd nanosheets exhibited excellent catalytic performances in the carbonylation of iodobenzene by carbon monoxide. The novel nanocomposites could be applied as model catalysts to explore electronic effects in catalysis.展开更多
We present a microscopic investigation on the structure-activity relationship of the Co-N4 site in the oxygen reduction reaction(ORR)by electrochemical scanning tunneling microscopy(ECSTM)at the molecular scale.The co...We present a microscopic investigation on the structure-activity relationship of the Co-N4 site in the oxygen reduction reaction(ORR)by electrochemical scanning tunneling microscopy(ECSTM)at the molecular scale.The cobalt porphyrins with various substituents(CoTPPX_(4),X=Cl,H,OCH_(3))that delicately regulate the electronic structure of the active site were investigatedasmodel catalysts.Electrochemical measurements evidenced that the CoTPPCl_(4)exhibits better activity,higher product selectivity for H_(2)O,and lower stability.The CoTPPX_(4)-O_(2)complex with higher contrast can be observed in the STM images and the proportion of the CoTPPCl_(4)-O_(2)is appreciably larger than that of CoTPP-O_(2)and CoTPP(OCH_(3))4-O_(2).Theoretical simulations of the model catalysts and the reaction processes of the ORR reveal the relationship between the electronic structure and the catalytic behavior of the model catalysts.The transformation of the CoTPPX_(4)-O_(2)and CoTPPX_(4)in the electrocatalytic reaction was monitored by in situ ECSTM characterization.The structure-activity relationship clarified by experimental and theoretical investigations in this work should help to guide the rational design and optimization of high-performance catalysts.展开更多
基金the National Natural Science Foundation of China(No.20744004 and No.20774025).
文摘As one of the most important catalysts in polyethylene industry,Phillips catalyst(CrO_x/SiO_2)was quite unique for its activation by ethylene monomer without using any activator like alkyl-aluminium or MAO.In this work,the density functional theory(DFT)calculation combined with paired interacting orbitals(PIO)method was applied for the theoretical studies on coordination reaction mechanism between ethylene monomer and two model catalysts namely Cr(Ⅱ)(OH)_2(M1) and silsesquioxane-supported Cr(Ⅱ)(M2)as surfac...
基金supported by the "Thousand Talents Program" of China, the Fok Ying-Tong Education Foundation for Outstanding Young Teachers in University, the National Natural Science Foundation of China (21573139, 21773146, 21902099, and 21905167)theChinaPostdoctoralScienceFoundation (2019M650232)+2 种基金the Fundamental Research Funds for the Central Universities (GK202003025)the Research Funds of Shaanxi Normal Universitythe Opening Fund of State Key Laboratory of Heavy Oil Processing。
文摘Transition-metal based M-N_4/C catalysts are appealing for electrocatalytic oxygen reduction reaction(ORR) and oxygen evolution reaction(OER). Employing model catalysts, which have well-defined molecular structures and coordination environments, to investigate electrocatalytic performance of M-N_4/C sites for ORR and OER is of fundamental significance. Herein, we reported the use of Co tetra(phenyl)porphyrin 1 and Co tetra(pentafluorophenyl)porphyrin 2 as models to probe the role of Co-N_4/C sites for oxygen electrocatalysis. We showed that Co porphyrin 1 is more efficient than its structural analogue 2 for oxygen electrocatalysis in alkaline aqueous solutions, indicating that the electronrich Co-N_4/C site is more favored when noncovalently adsorbed on carbon supports. This work inspires rational design of reaction-oriented catalysts for sustainable energy storage and conversion technologies.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.21872131,22106085,U1832218,and U1932214)the National Key Research and Development Program of China(No.2019YFA0405601)。
文摘Selective catalytic reduction of NO by CO is challenging in environmental catalysis but attractive owing to the advantage of simultaneous elimination of NO and CO.Here,model catalysts consisting of Pd nanoparticles(NPs)and single-atom Pd supported on a CeO_(2)(111)film grown on Cu(111)(denoted as Pd NPs/CeO_(2)and Pd_(1)/CeO_(2),respectively)were successfully prepared and characterized by synchrotron radiation photoemission spectroscopy(SRPES)and infrared reflection absorption spectroscopy(IRAS).The NO+CO adsorption/reaction on the Pd_(1)/CeO_(2)and Pd NPs/CeO_(2)catalysts were carefully investigated using SRPES,temperature-programmed desorption(TPD),and IRAS.It is found that the reaction products on both model catalysts are in good agreement with those on real catalysts,demonstrating the good reliability of using these model catalysts to study the reaction mechanism of the NO+CO reaction.On the Pd NPs/CeO_(2)surface,N_(2)is formed by the combination of atomic N coming from the dissociation of NO on Pd NPs at higher temperatures.N_(2)O formation occurs probably via chemisorbed NO combined with atomic N on the surface.While on the single-atom Pd_(1)/CeO_(2)surface,no N_(2)O is detected.The 100%N_(2)selectivity may stem from the formation of O-N-N-O^(*)intermediate on the surface.Through this study,direct experimental evidence for the reaction mechanisms of the NO+CO reaction is provided,which supports the previous density functional theory(DFT)calculations.
基金We are grateful for financial support from the“Hundred Talents Program”of the Chinese Academy of Sciences and the“Young Talents Training Program”of the Shanghai Branch of the Chinese Academy of Sciences.We acknowledge the financial support from the National Science Youth Foundation of China(22202205)Xiamen City Natural Science Foundation of China(3502Z20227256)Fujian Provincial Natural Science Foundation of China(2022J01502).
文摘Metal-free carbon,as the most representative heterogeneous metal-free catalysts,have received considerable interests in electro-and thermo-catalytic reac-tions due to their impressive performance and sustainability.Over the past decade,well-designed carbon catalysts with tunable structures and heteroatom groups coupled with various characterization techniques have proposed numerous reaction mechanisms.However,active sites,key intermediate species,precise structure-activity relationships and dynamic evolution processes of carbon catalysts are still rife with controversies due to the monotony and limitation of used experimental methods.In this Review,we sum-marize the extensive efforts on model catalysts since the 2000s,particularly in the past decade,to overcome the influences of material and structure limitations in metal-free carbon catalysis.Using both nanomolecule model and bulk model,the real contribution of each alien species,defect and edge configuration to a series of fundamentally important reactions,such as thermocatalytic reactions,electrocatalytic reactions,were systematically studied.Combined with in situ techniques,isotope labeling and size control,the detailed reaction mechanisms,the precise 2D structure-activity relationships and the rate-determining steps were revealed at a molecular level.Furthermore,the outlook of model carbon catalysis has also been proposed in this work.
基金This work is financially supported by the National Natural Science Foundation of China(No.22102146)the Natural Science Foundation of Zhejiang Province(No.LQ20B030007)self-designed scientific research project of Zhejiang Normal University(No.2021ZS0602).
文摘Comprehensive Summary Recent progress in colloidal synthesis has realized the preparations of uniform nanocrystal(NC)model catalysts with rich and well-controlled morphologies that were employed to explore structure-activity relationships of powder catalysts,similar to single-crystal-based model catalysts under ultrahigh vacuum conditions but can work at the same conditions as powder catalysts without the"materials gap"and"pressure gap".In this perspective,the CeO_(2)-based NC model catalysts with various morphologies are included and their relevant progresses are critically reviewed.The detailed descriptions of morphology-controlled synthesis and characterizations of uniform CeO_(2)NCs.
基金supported by the National Natural Science Foundation of China (Nos.21802096,21832004,21902179,21991152,and 21991150)the Shanghai XFEL Beamline Project (SBP) (31011505505885920161A2101001)the support of the Shanghai Sailing Program (19YF1455600)。
文摘An in-depth understanding of the structure-activity relationship between the surface structure,chemical composition,adsorption and desorption of molecules,and their reaction activity and selectivity is necessary for the rational design of high-performance catalysts.Herein,we present a method for studying catalytic mechanisms using a combination of in situ reaction cells and surface science techniques.The proposed system consists of four parts:preparation chamber,temperatureprogrammed desorption(TPD)chamber,quick load-lock chamber,and in situ reaction cell.The preparation chamber was equipped with setups based on the surface science techniques used for standard sample preparation and characterization,including an Ar+sputter gun,Auger electron spectrometer,and a low-energy electron diffractometer.After a well-defined model catalyst was prepared,the sample was transferred to a TPD chamber to investigate the adsorption and desorption of the probe molecule,or to the reaction cell,to measure the catalytic activity.A thermal desorption experiment for methanol on a clean Cu(111)surface was conducted to demonstrate the functionality of the preparation and TPD chambers.Moreover,the repeatability of the in situ reaction cell experiment was verified by CO_(2) hydrogenation on the Ni(110)surface.At a reaction pressure of 800 Torr at 673 K,turnover frequencies for the methanation reaction and reverse water-gas shift reaction were 0.15 and 7.55 Ni atom^(-1) s^(-1),respectively.
基金This work was supported by National Natural Science Foundation of China(NSFC)(Nos.10979031,20921001,and 90606006)the“973”State Key Project(No.2006CB932303)and the China Postdoctoral Science Foundation(No.20080440361).
文摘CO oxidation has been performed on Co_(3)O_(4) nanobelts and nanocubes as model catalysts.The Co_(3)O_(4) nanobelts which have a predominance of exposed{011}planes are more active than Co_(3)O_(4) nanocubes with exposed{001}planes.Temperature programmed reduction of CO shows that Co_(3)O_(4) nanobelts have stronger reducing properties than Co_(3)O_(4) nanocubes.The essence of shape and crystal plane effect is revealed by the fact that turnover frequency of Co3+sites of{011}planes on Co_(3)O_(4) nanobelts is far higher than that of{001}planes on Co_(3)O_(4) nanocubes.
基金supported by the National Natural Science Foundation of China (U1732267)Shanghai Science and Technology Development Funds (22YF1454500)Photon Science Center for Carbon Neutrality and Low-Carbon Conversion Science and Engineering Center。
文摘Understanding the atomic and electronic changes of active sites promotes the whole new sight into electrochemical carbon dioxide reduction reaction(CO_(2)RR),which provides a feasible strategy to achieve carbon neutrality.Here we employ operando high-energy resolution fluorescence-detected Xray absorption spectroscopy(HERFD-XAS)to track the structural evolution of Ni(II)phthalocyanine(NiPc),considered as the model catalysts with uniform Ni-N_(4)-C_(8) moiety,during the CO_(2)RR.The HERFD-XAS method is in favor of elucidating the interaction of the reactant/catalyst interface from the atomic electronic structure dimension,facilitating the establishment of the catalytic mechanism and the dynamic structure changes.Based on operando measurement,surface sensitive difference spectra(△μ)and spectroscopy simulation,the interfacial interactions between the active sites of NiPc and reactants are monitored and the Ni species gradually reduced by increasing the applied potential is discovered.HERFD-XAS method offers an advanced and powerful tool for elucidating the complex catalytic mechanism in further various systems.
基金The authors acknowledge support of Iran Initiative Nanotechnology Council for this projectassistance of the personnel of Instrumental Analysis Laboratory and Central Laboratory of Amirkabir University of Technology(Tehran Polytechnic).
文摘A solvothermal method was used to synthesize MIL-101(Fe)and MIL-88(Fe),which were used for alkylation of benzene.The synthesized catalysts were characterized by X-ray diffraction,Fourier transform infrared spectroscopy,field emission scanning electron microscope,dynamic light scattering,and BET techniques.Metal-organic frameworks(MOFs)were modeled to investigate the catalytic performance and existence of mass transfer limitations.Calculated effectiveness factors revealed absence of internal a nd external mass transfer.Sensitivity analysis revealed best operating conditions over MIL-101 at 120℃ and 5 bar and over MIL-88 at 142℃ and 9 bar.
文摘Inverse oxide/metal model systems are frequently used to investigate catalytic structure-function relationships at an atomic level.By means of a novel atomic layer deposition process,growth of single-site Fe_(1)O_(x) on a Pt(111)single crystal surface was achieved,as confirmed by scanning tunneling microscopy(STM).The redox properties of the catalyst were characterized by synchrotron radiation based ambient pressure X-ray photoelectron spectroscopy(AP-XPS).After calcination treatment at 373 K in 1 mbar O_(2).the chemical state of the catalyst was determined as Fe^(3+).Reduction in 1 mbar H_(2) at 373 K demonstrates a facile reduction to Fe2+and complete hydroxylation at significantly lower temperatures than what has been reported for iron oxide nanoparticles.At reaction conditions relevant for preferential oxidation of CO in H_(2)(PROX),the catalyst exhibits a Fe3+state(ferric hydroxide)at 298 K while re-oxidation of iron oxide clusters does not occur under the same condition.CO oxidation proceeds on the single-site Fei(OH)3 through a mechanism including the loss of hydroxyl groups in the temperature range of 373 to 473 K,but no reaction is observed on iron oxide clusters.The results highlight the high flexibility of the single iron atom catalyst in switching oxidation states,not observed for iron oxide nanoparticles under similar reaction conditions,which may indicate a higher intrinsic activity of such single interfacial sites than the conventional metal-oxide interfaces.In summary,our findings of the redox properties on inverse single-site iron oxide model catalyst may provide new insights into applied Fe-Pt catalysis.
文摘Electronic adjustment is one of the most commonly used strategies to improve the catalytic performance of heterogeneous catalysts. We prepared hexagonal ultrathin Pd nanosheets with edges modified by gold nanoparticles (Au@Pd nanosheets) using galvanic replacement method. By virtue of the electronic interactions between the Pd nanosheets and Au nanoparticles, the Au@Pd nanosheets exhibited excellent catalytic performances in the carbonylation of iodobenzene by carbon monoxide. The novel nanocomposites could be applied as model catalysts to explore electronic effects in catalysis.
基金supported by the National Key R&D Program of China(grant no.2021YFA1501002)the National Natural Science Foundation of China(grant nos.22132007,21972147,21725306)+1 种基金the Key Research Program of the Chinese Academy of Sciences(grant no.XDPB01)the National Postdoctoral Program for Innovative Talents(grant no.BX20220307)of the Chinese Postdoctoral Science Foundation.
文摘We present a microscopic investigation on the structure-activity relationship of the Co-N4 site in the oxygen reduction reaction(ORR)by electrochemical scanning tunneling microscopy(ECSTM)at the molecular scale.The cobalt porphyrins with various substituents(CoTPPX_(4),X=Cl,H,OCH_(3))that delicately regulate the electronic structure of the active site were investigatedasmodel catalysts.Electrochemical measurements evidenced that the CoTPPCl_(4)exhibits better activity,higher product selectivity for H_(2)O,and lower stability.The CoTPPX_(4)-O_(2)complex with higher contrast can be observed in the STM images and the proportion of the CoTPPCl_(4)-O_(2)is appreciably larger than that of CoTPP-O_(2)and CoTPP(OCH_(3))4-O_(2).Theoretical simulations of the model catalysts and the reaction processes of the ORR reveal the relationship between the electronic structure and the catalytic behavior of the model catalysts.The transformation of the CoTPPX_(4)-O_(2)and CoTPPX_(4)in the electrocatalytic reaction was monitored by in situ ECSTM characterization.The structure-activity relationship clarified by experimental and theoretical investigations in this work should help to guide the rational design and optimization of high-performance catalysts.