Electrochemical CO_(2) reduction to produce value-added chemicals and fuels is one of the research hotspots in the field of energy conversion.The development of efficient catalysts with high conductivity and readily a...Electrochemical CO_(2) reduction to produce value-added chemicals and fuels is one of the research hotspots in the field of energy conversion.The development of efficient catalysts with high conductivity and readily accessible active sites for CO_(2) electroreduction remains challenging yet indispensable.In this work,a reliable poly(ethyleneimine)(PEI)-assisted strategy is developed to prepare a hollow carbon nanocomposite comprising a single-site Ni-modified carbon shell and confined Ni nanoparticles(NPs)(denoted as Ni@NHCS),where PEI not only functions as a mediator to induce the highly dispersed growth of Ni NPs within hollow carbon spheres,but also as a nitrogen precursor to construct highly active atomically-dispersed Ni-Nx sites.Benefiting from the unique structural properties of Ni@NHCS,the aggregation and exposure of Ni NPs can be effectively prevented,while the accessibility of abundant catalytically active Ni-Nx sites can be ensured.As a result,Ni@NHCS exhibits a high CO partial current density of 26.9 mA cm^(-2) and a Faradaic efficiency of 93.0% at-1.0 V vs.RHE,outperforming those of its PEI-free analog.Apart from the excellent activity and selectivity,the shell confinement effect of the hollow carbon sphere endows this catalyst with long-term stability.The findings here are anticipated to help understand the structure-activity relationship in Ni-based carbon catalyst systems for electrocatalytic CO_(2) reduction.Furthermore,the PEI-assisted synthetic concept is potentially applicable to the preparation of high-performance metal-based nanoconfined materials tailored for diverse energy conversion applications and beyond.展开更多
The development of reliable catalysts with both excellent activity and recyclability for carbon dioxide(CO_(2))hydrogenation is challenging.Herein,a ternary hybrid heterogeneous catalyst,involving mononuclear Ru compl...The development of reliable catalysts with both excellent activity and recyclability for carbon dioxide(CO_(2))hydrogenation is challenging.Herein,a ternary hybrid heterogeneous catalyst,involving mononuclear Ru complex,N,P-containing porous organic polymers(POPs),and mesoporous hollow carbon spheres(Ru^(3+)-POPs@MHCS)is reported for CO_(2)hydrogenation to formate.Based on comprehensive structural analyses,we demonstrated that Ru^(3+)-POPs were successfully immobilized within MHCS.The optimized Ru^(3+)-0.5POPs@MHCS catalyst,which was obtained with about 5 wt.%Ru^(3+)and 0.5 mmol POPs polymers confined into 0.3 g MHCS,exhibited high catalytic activity for CO_(2)hydrogenation to formate(turnover number(TON)>1,200 for 24 h under mild reaction conditions(4.0 MPa,120℃))and improved durability,compared to Ru^(3+)catalysts without POPs polymers(Ru^(3+)-MHCS)and unencapsulated MHCS(Ru^(3+)-0.5POPs)catalysts.The improved catalytic performance is attributed to the high surface area and large pore volume of MHCS which favors dispersion and stabilization of Ru^(3+)-POPs.Furthermore,the MHCS and POPs showed high CO_(2)adsorption ability.Ru^(3+)-POPs encapsulated into MHCS reduces the activation energy barrier for CO_(2)hydrogenation to formate.展开更多
Understanding the behavior of matter at extreme pressures of the order of a megabar(Mbar)is essential to gain insight into various physical phenomena at macroscales—the formation of planets,young stars,and the cores ...Understanding the behavior of matter at extreme pressures of the order of a megabar(Mbar)is essential to gain insight into various physical phenomena at macroscales—the formation of planets,young stars,and the cores of super-Earths,and at microscales—damage to ceramic materials and high-pressure plastic transformation and phase transitions in solids.Under dynamic compression of solids up to Mbar pressures,even a solid with high strength exhibits plastic properties,causing the induced shock wave to split in two:an elastic precursor and a plastic shock wave.This phenomenon is described by theoretical models based on indirect measurements of material response.The advent of x-ray free-electron lasers(XFELs)has made it possible to use their ultrashort pulses for direct observations of the propagation of shock waves in solid materials by the method of phase-contrast radiography.However,there is still a lack of comprehensive data for verification of theoretical models of different solids.Here,we present the results of an experiment in which the evolution of the coupled elastic-plastic wave structure in diamond was directly observed and studied with submicrometer spatial resolution,using the unique capabilities of the x-ray free-electron laser(XFEL).The direct measurements allowed,for the first time,the fitting and validation of the 2D failure model for diamond in the range of several Mbar.Our experimental approach opens new possibilities for the direct verification and construction of equations of state of matter in the ultra-high-stress range,which are relevant to solving a variety of problems in high-energy-density physics.展开更多
Tight focusing with very small f-numbers is necessary to achieve the highest at-focus irradiances.However,tight focusing imposes strong demands on precise target positioning in-focus to achieve the highest on-target i...Tight focusing with very small f-numbers is necessary to achieve the highest at-focus irradiances.However,tight focusing imposes strong demands on precise target positioning in-focus to achieve the highest on-target irradiance We describe several near-infrared,visible,ultraviolet and soft and hard X-ray diagnostics employed in a~10^(22)W/cm^(2)laser±plasma experiment.We used nearly 10 J total energy femtosecond laser pulses focused into an approximately1.3-μm focal spot on 5±20μm thick stainless-steel targets.We discuss the applicability of these diagnostics to determine the best in-focus target position with approximately 5μm accuracy(i.e.,around half of the short Rayleigh length)and show that several diagnostics(in particular,3ωreflection and on-axis hard X-rays)can ensure this accuracy.We demonstrated target positioning within several micrometers from the focus,ensuring over 80%of the ideal peak laser intensity on-target.Our approach is relatively fast(it requires 10±20 laser shots)and does not rely on the coincidence of low-power and high-power focal planes.展开更多
Knowledge about electronic structures is important to gain an understanding of the unique functional properties of diradicaloids.In this study,we synthesized and characterized a diradicaloid in which two phenalenyl ra...Knowledge about electronic structures is important to gain an understanding of the unique functional properties of diradicaloids.In this study,we synthesized and characterized a diradicaloid in which two phenalenyl radical sites are coupled antiferromagnetically via a through-space interaction.The results of quantum chemical,physicochemical(^(1)H NMR,electronic absorption,cyclic voltammetry,SQUID,ESR),and chemical reactivity studies show that this diradicaloid has singlet diradical character.An assessment of the nature of the bonding interaction between two radical sites in this species using DFT calculations demonstrates that a small spatial overlap between the two SOMOs in this diradicaloid provides an efficient electron exchange path for the singlet state to be substantially lower in energy than the triplet state.展开更多
Since the discovery of the triphenylmethyl(trityl)cation 120 years ago,a variety of aromatic cations having various colors and luminescence properties have been rigorously studied.Many,differently substituted trityl c...Since the discovery of the triphenylmethyl(trityl)cation 120 years ago,a variety of aromatic cations having various colors and luminescence properties have been rigorously studied.Many,differently substituted trityl cations have been synthesized,and their optical properties have been elucidated.However,the optical properties of the parent,non-substituted and highly reactive trityl cation,which was observed to be very weakly luminescent,have not been subjected to detailed investigation.In the effort described herein,we explored the optical nature of non-substituted trityl hexafluorophosphate(PF_(6))in the crystalline state.Trityl PF_(6) was found to exist as two crystal polymorphs including a yellow(Y)and an orange(O)form.Moreover,we observed that these crystalline forms display crystalline-state emission with different colors.The results of X-ray crystallographic analysis showed that the two polymorphs have totally different molecular packing arrangements.Furthermore,an investigation of their optical properties revealed that the O-crystal undergoes a distinct color change to yellow upon cooling as a consequence of a change in the nature of the charge transfer interaction between the cation and PF6 anion,and that both the Y-and O-crystal exhibit phosphorescence.展开更多
文摘Electrochemical CO_(2) reduction to produce value-added chemicals and fuels is one of the research hotspots in the field of energy conversion.The development of efficient catalysts with high conductivity and readily accessible active sites for CO_(2) electroreduction remains challenging yet indispensable.In this work,a reliable poly(ethyleneimine)(PEI)-assisted strategy is developed to prepare a hollow carbon nanocomposite comprising a single-site Ni-modified carbon shell and confined Ni nanoparticles(NPs)(denoted as Ni@NHCS),where PEI not only functions as a mediator to induce the highly dispersed growth of Ni NPs within hollow carbon spheres,but also as a nitrogen precursor to construct highly active atomically-dispersed Ni-Nx sites.Benefiting from the unique structural properties of Ni@NHCS,the aggregation and exposure of Ni NPs can be effectively prevented,while the accessibility of abundant catalytically active Ni-Nx sites can be ensured.As a result,Ni@NHCS exhibits a high CO partial current density of 26.9 mA cm^(-2) and a Faradaic efficiency of 93.0% at-1.0 V vs.RHE,outperforming those of its PEI-free analog.Apart from the excellent activity and selectivity,the shell confinement effect of the hollow carbon sphere endows this catalyst with long-term stability.The findings here are anticipated to help understand the structure-activity relationship in Ni-based carbon catalyst systems for electrocatalytic CO_(2) reduction.Furthermore,the PEI-assisted synthetic concept is potentially applicable to the preparation of high-performance metal-based nanoconfined materials tailored for diverse energy conversion applications and beyond.
基金supported by JSPS KAKENHI(Nos.18K14056 and 19H00838)JST,PRESTO(No.JPMJPR19T3)+3 种基金Japan.A part of this work was supported by the cooperative research program of“Network Joint Research Center for Materials and Devices”(No.20211069).support of the International Joint Research Promotion Program at Osaka University.G.X.Y.gratefully acknowledges the financial support from the China Scholarship Council(No.201808310132)Y.K.,K.M.,and H.Y.thank the Elements Strategy Initiative of MEXT(No.JPMXP0112101003)Japan.The synchrotron radiation experiments for XAFS measurement were performed at the BL01B1 beamline in SPring-8 with approval from JASRI(Nos.2019B1114 and 2020A1064).
文摘The development of reliable catalysts with both excellent activity and recyclability for carbon dioxide(CO_(2))hydrogenation is challenging.Herein,a ternary hybrid heterogeneous catalyst,involving mononuclear Ru complex,N,P-containing porous organic polymers(POPs),and mesoporous hollow carbon spheres(Ru^(3+)-POPs@MHCS)is reported for CO_(2)hydrogenation to formate.Based on comprehensive structural analyses,we demonstrated that Ru^(3+)-POPs were successfully immobilized within MHCS.The optimized Ru^(3+)-0.5POPs@MHCS catalyst,which was obtained with about 5 wt.%Ru^(3+)and 0.5 mmol POPs polymers confined into 0.3 g MHCS,exhibited high catalytic activity for CO_(2)hydrogenation to formate(turnover number(TON)>1,200 for 24 h under mild reaction conditions(4.0 MPa,120℃))and improved durability,compared to Ru^(3+)catalysts without POPs polymers(Ru^(3+)-MHCS)and unencapsulated MHCS(Ru^(3+)-0.5POPs)catalysts.The improved catalytic performance is attributed to the high surface area and large pore volume of MHCS which favors dispersion and stabilization of Ru^(3+)-POPs.Furthermore,the MHCS and POPs showed high CO_(2)adsorption ability.Ru^(3+)-POPs encapsulated into MHCS reduces the activation energy barrier for CO_(2)hydrogenation to formate.
基金We thank the technical staff of SACLA for their support during the experiment.The experiment was performed at BL3 of SACLA with the approval of the Japan Synchrotron Radiation Research Institute(Proposal Nos.2021A8004 and 2021B8002).The high-power drive laser installed in SACLA EH5 was developed with the cooperation of Hamamatsu Photonics.The installation of diffractive optical elements to improve the smoothness of the drive laser-pattern was supported by the SACLA Basic Development ProgramThe work was carried out with the financial support of the Russian Federation represented by the Ministry of Science and Higher Education of the Russian Federation(Grant No.075-15-2021-1352)This work was supported by KAKENHI(Grant Nos.17K05729 and 21K03499)from the Japan Society for the Promotion of Science(JSPS).
文摘Understanding the behavior of matter at extreme pressures of the order of a megabar(Mbar)is essential to gain insight into various physical phenomena at macroscales—the formation of planets,young stars,and the cores of super-Earths,and at microscales—damage to ceramic materials and high-pressure plastic transformation and phase transitions in solids.Under dynamic compression of solids up to Mbar pressures,even a solid with high strength exhibits plastic properties,causing the induced shock wave to split in two:an elastic precursor and a plastic shock wave.This phenomenon is described by theoretical models based on indirect measurements of material response.The advent of x-ray free-electron lasers(XFELs)has made it possible to use their ultrashort pulses for direct observations of the propagation of shock waves in solid materials by the method of phase-contrast radiography.However,there is still a lack of comprehensive data for verification of theoretical models of different solids.Here,we present the results of an experiment in which the evolution of the coupled elastic-plastic wave structure in diamond was directly observed and studied with submicrometer spatial resolution,using the unique capabilities of the x-ray free-electron laser(XFEL).The direct measurements allowed,for the first time,the fitting and validation of the 2D failure model for diamond in the range of several Mbar.Our experimental approach opens new possibilities for the direct verification and construction of equations of state of matter in the ultra-high-stress range,which are relevant to solving a variety of problems in high-energy-density physics.
基金financial support from ELI-Beamlinesproject Advanced Research using High Intensity Laser Produced Photons and Particles(ADONIS)(Project No.CZ.02.1.01/0.0/0.0/16_019/0000789)from the European Regional Development Fund+5 种基金QST-IRIthe QST President’s Strategic Grant(Creative Research)JSPS KAKENHI JP17F17811,JP19KK0355,JP19H00669 and JP22H01239the Czech Ministry of EducationYouth and Sports(CMEYS)for the financial support of the project number LM2023068partly supported by JSPS KAKENHI Grant No.JP23H01151。
文摘Tight focusing with very small f-numbers is necessary to achieve the highest at-focus irradiances.However,tight focusing imposes strong demands on precise target positioning in-focus to achieve the highest on-target irradiance We describe several near-infrared,visible,ultraviolet and soft and hard X-ray diagnostics employed in a~10^(22)W/cm^(2)laser±plasma experiment.We used nearly 10 J total energy femtosecond laser pulses focused into an approximately1.3-μm focal spot on 5±20μm thick stainless-steel targets.We discuss the applicability of these diagnostics to determine the best in-focus target position with approximately 5μm accuracy(i.e.,around half of the short Rayleigh length)and show that several diagnostics(in particular,3ωreflection and on-axis hard X-rays)can ensure this accuracy.We demonstrated target positioning within several micrometers from the focus,ensuring over 80%of the ideal peak laser intensity on-target.Our approach is relatively fast(it requires 10±20 laser shots)and does not rely on the coincidence of low-power and high-power focal planes.
基金the JSPS for KAKENHI funding(Grant No.JP21H01918 and JP20K21194)a Grant-in-Aid for Transformative Research Areas(A)“Condensed Conjugation”(JSPS for KAKENHI funding Grant No.JP20H05865)from MEXT,Japan.
文摘Knowledge about electronic structures is important to gain an understanding of the unique functional properties of diradicaloids.In this study,we synthesized and characterized a diradicaloid in which two phenalenyl radical sites are coupled antiferromagnetically via a through-space interaction.The results of quantum chemical,physicochemical(^(1)H NMR,electronic absorption,cyclic voltammetry,SQUID,ESR),and chemical reactivity studies show that this diradicaloid has singlet diradical character.An assessment of the nature of the bonding interaction between two radical sites in this species using DFT calculations demonstrates that a small spatial overlap between the two SOMOs in this diradicaloid provides an efficient electron exchange path for the singlet state to be substantially lower in energy than the triplet state.
基金JSPSKAKENHI Grant-in-Aid for Scientific Research(C),Grant/Award Number:JP20K05475(Tomohiko Nishiuchi)Scientific Research(B),Grant/Award Number:JP21H01887(Kenji Kamada)。
文摘Since the discovery of the triphenylmethyl(trityl)cation 120 years ago,a variety of aromatic cations having various colors and luminescence properties have been rigorously studied.Many,differently substituted trityl cations have been synthesized,and their optical properties have been elucidated.However,the optical properties of the parent,non-substituted and highly reactive trityl cation,which was observed to be very weakly luminescent,have not been subjected to detailed investigation.In the effort described herein,we explored the optical nature of non-substituted trityl hexafluorophosphate(PF_(6))in the crystalline state.Trityl PF_(6) was found to exist as two crystal polymorphs including a yellow(Y)and an orange(O)form.Moreover,we observed that these crystalline forms display crystalline-state emission with different colors.The results of X-ray crystallographic analysis showed that the two polymorphs have totally different molecular packing arrangements.Furthermore,an investigation of their optical properties revealed that the O-crystal undergoes a distinct color change to yellow upon cooling as a consequence of a change in the nature of the charge transfer interaction between the cation and PF6 anion,and that both the Y-and O-crystal exhibit phosphorescence.