Lewis acid(LA)and Lewis base(LB)sites on catalyst surfaces play a pivotal role in catalytic reactions.By precisely modulating the type,density,and spatial distribution of these Lewis acid/base sites,catalytic performa...Lewis acid(LA)and Lewis base(LB)sites on catalyst surfaces play a pivotal role in catalytic reactions.By precisely modulating the type,density,and spatial distribution of these Lewis acid/base sites,catalytic performance indicators such as catalytic activity,selectivity,and stability can be effectively optimized.As a result,they become essential parameters that must be considered in the design and development of high-efficiency catalysts.This study proposes a surface engineering method to accurately control the concentration of surface LA and LB sites in defect-laden In_(2)O_(3-x)(OH)_(y)(denoted as N-n%-IO),establishing three types of LB/LA stoichiometric ratios with different photocatalytic CO_(2)hydrogenation performances.It is demonstrated that the LB-rich system(LB/LA>1)shows suppressed activity.In contrast,the balanced stoichiometric ratio system(LB/LA=1)attains an optimal methanol yield(179.79μmol g^(-1)h^(-1))and selectivity(43.67%),while the LA-rich system(LB/LA<1)exhibits the best CO production rate(1913.76μmol g^(-1)h^(-1))and selectivity(94.96%).Systematic experiments disclose that the balanced LB/LA system with adjacent surface frustrated Lewis pairs(SFLPs)can effectively facilitate the adsorption/activation of reactants,stabilize intermediates,and regulate the dynamic behavior of photo-generated carriers.However,the imbalanced LB/LA systems either lack necessary active sites or can only follow an oxygen vacancy-mediated pathway during photocatalytic CO_(2)hydrogenation.This work offers a comprehensive understanding of the crucial functions of surface Lewis acid/base sites in the product distribution of solar-driven CO_(2)reduction.展开更多
The Jellium closed-shell model,a cornerstone of cluster science,has long guided the design of superatoms by dictating electron-counting rules.However,its reliance on precise control of cluster composition and electron...The Jellium closed-shell model,a cornerstone of cluster science,has long guided the design of superatoms by dictating electron-counting rules.However,its reliance on precise control of cluster composition and electron shell occupancy presents significant experimental challenges.Here,we introduce a ligation strategy that circumvents these limitations by demonstrating that the adiabatic electron affinity(AEA) of aluminum-based clusters,whether with filled or partially filled electron shells,can be dramatically enhanced through the attachment of organic Lewis acid ligands.It was evidenced that the AEA of PAl12can be significantly increased by 2.17 e V after the ligation of two ligands,indicating a remarkable improvement in its electron-accepting ability.This approach yields superhalogen species,offering a versatile and practical means to tune the electronic properties of clusters while preserving their superatomic states,independent of shell occupancy.Remarkably,this ligand-induced modulation is not confined to naked clusters but also extends to nano-confined systems,hinting at its broader applicability.Given the indispensable role of ligands in cluster synthesis,this strategy holds promise for advancing the field of condensed-phase superatom synthesis,potentially complementing traditional electron-counting rules in a broader range of applications.展开更多
Ceramic cells promise ideal energy conversion and storage devices,making the development of efficient and robust air electrodes crucial for their application.In this study,a Ba_(0.4)Sr_(0.5)Cs_(0.1)Co_(0.7)Fe_(0.2)Nb_...Ceramic cells promise ideal energy conversion and storage devices,making the development of efficient and robust air electrodes crucial for their application.In this study,a Ba_(0.4)Sr_(0.5)Cs_(0.1)Co_(0.7)Fe_(0.2)Nb_(0.1)O_(3−δ)(BSCCFN)air electrode,based on Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3−δ)(BSCF),is designed using a perovskite A-B-site ionic Lewis acid strength(ISA)polarization distribution strategy and is successfully applied in both oxygen-ion conducting solid oxide fuel cells(O-SOFCs)and proton-conducting reversible protonic ceramic cells(R-PCCs).When BSCCFN is used as the air electrode in O-SOFCs,a peak power density(PPD)of 1.45 W cm^(−2)is achieved at 650°C,whereas in R-PCCs,a PPD of 1.13 W cm^(−2)and a current density of−1.8 A cm^(−2)at 1.3 V are achieved at the same temperature and show stable reversibility over 100 h.Experimental measurements and theoretical calculations demonstrate that low-ISA Cs+doping accelerates the reaction kinetics of both oxygen ions and protons,while high-ISA Nb^(5+)doping enhances electrode stability.The synergistic effect of Cs^(+)and Nb^(5+)co-doping in the BSCCFN electrode lies in the ISA polarization distribution,which weakens the Co/Fe–O bond covalency,thereby promoting oxygen vacancy formation and facilitating the conduction of oxygen ions and protons.展开更多
The high-efficiency conversion of biomass resources to biofuels has attracted widespread attention, and the active sites and synergistic effect of catalysts significantly impact their surface arrangement and electroni...The high-efficiency conversion of biomass resources to biofuels has attracted widespread attention, and the active sites and synergistic effect of catalysts significantly impact their surface arrangement and electronic structure. Here, a nickel-based transition metal carbide catalyst(Ni/TMC) with high Lewis acidity was prepared by self-assembly of transition metal carbide(TMC) and nickel, which exhibited excellent performance on synergistic hydrogenation and hydrogenolysis of 5-hydroxymethylfurfural(HMF) into liquid biofuel 2,5-dimethylfuran(DMF).Notably, Ni/WC with the highest Lewis acidity(4728.3 μmol g^(-1)) can achieve 100% conversion of HMF to 97.6% yield of DMF, with a turnover frequency of up to 46.5 h^(-1). The characterization results demonstrate that the rich Lewis acid sites yielded by the synergistic effect between Ni species and TMC are beneficial for the C=O hydrogenation and C–O cleavage, thereby accelerating the process of hydrodeoxygenation(HDO). Besides, a kinetic model for the HDO of HMF to DMF process has been established based on the experimental results, which elucidated a significant correlation between the measured and the predicted data(R^(2)> 0.97). Corresponding to the adsorption configuration of Ni/WC and substrate determined by in-situ FTIR characterization, this study provides a novel insight into the selective conversion of HMF process for functional biofuel and bio-chemicals.展开更多
High-capacity LiBH_(4)is a promising solid hydrogen storage material.However,the large electron cloud density between the B-H bonds in LiBH_(4)induces high dehydrogenation temperatures and sluggish dehydrogenation kin...High-capacity LiBH_(4)is a promising solid hydrogen storage material.However,the large electron cloud density between the B-H bonds in LiBH_(4)induces high dehydrogenation temperatures and sluggish dehydrogenation kinetics.To solve the above problems,it is proposed to enhance the hydrogen storage properties of LiBH_(4)through the synergistic effect of Brønsted and Lewis acid in Hβzeolite.Composite hydrogen storage systems with different mass ratios were prepared by simple ball-milling.At a LiBH_(4)-to-Hβmass ratio of 6:4,the 6LiBH_(4)-4Hβsystem released hydrogen at 190℃and achieved a hydrogen release capacity of 7.0 wt%H_(2)upon heating to 400℃.More importantly,the hydrogen release capacity of the system reached 6.02 wt%at 350℃under isothermal conditions after 100 min and 7.2 wt%at 400℃under isothermal conditions after 80 min,whereas the pristine LiBH_(4)only achieved 2.2 wt%.The improvement in hydrogen storage performance of the system was mainly attributed to two factors:(i)Lewis acid sites with acceptable electrons in the Hβweaken the electron density of B-H bonds in LiBH_(4),and(ii)the H+proton from the Brønsted acid sites and H−of LiBH_(4)undergo a H^(+)+H^(−)=H_(2)reaction.Theoretical calculations revealed that the Lewis and Brønsted acid sites in the Hβzeolite are conducive to the weakening of B-H bonds and that storage charge transfer occurs near the Lewis acid sites.The present work provides new insights into improving the hydrogen storage performance of LiBH_(4)by weakening the B-H bonds in the LiBH_(4).展开更多
This study employs density functional theory(DFT)calculations to systematically investigate the B‒H bond dissociation enthalpies(BDEs)of Lewis base‒borane complexes.A rigorous benchmark analysis identified theωB97XD/...This study employs density functional theory(DFT)calculations to systematically investigate the B‒H bond dissociation enthalpies(BDEs)of Lewis base‒borane complexes.A rigorous benchmark analysis identified theωB97XD/cc-pVTZ method as a reliable method for accurate prediction of B–H BDEs.An examination of more than 200 structurally diverse complexes across five major classes revealed that the type of Lewis base significantly influences the BDEs,with the order of amine–borane>phosphine–borane>N-heterocyclic carbene–borane>pyridine–borane.Solventstabilized boranes exhibit the broadest range of BDE values due to the diverse coordination modes of solvent molecules with borane.Further analysis revealed that the BDE values are synergistically affected by skeletal and substituent effects.Notably,a strong linear correlation(R^(2) up to 0.97)between the spin density of boryl radicals and BDEs,except for amine–boranes,provides a robust predictive model.This research enhances the fundamental understanding of B‒H bond dissociation properties in Lewis base–boranes and provides valuable insights for the development of new boron-based methodologies in organic synthesis.展开更多
Heterogeneous solid frustrated-Lewis-pair(FLP)catalyst is of great promise in practical hydrogenation applications.It has been found that all-solid FLPs can be created on ceria via surface oxygen vacancy regulation.Co...Heterogeneous solid frustrated-Lewis-pair(FLP)catalyst is of great promise in practical hydrogenation applications.It has been found that all-solid FLPs can be created on ceria via surface oxygen vacancy regulation.Consequently,it is desired to investigate the mechanisms of the FLP-catalyzed hydrogenation of C=C and C=O and provide insight into the modification of CeO_(2)catalysts for the selective hydrogenation.In this work,the reaction mechanism of the hydrogenation of CH_(2)=CH_(2)and CH_(3)CH=O at the FLP sites constructed on CeO_(2)(110)surface was investigated by density functional theory(DFT),with the classical Lewis acid-base pairs(CLP)site as the reference.The results illustrate that at the CLP site,the dissociated hydride(H^(δ−))forms a stable H−O bond with the surface O atom,while at the FLP site,H^(δ−)is stabilized by Ce,displaying higher activity on the one hand.On the other hand,the electron cloud density of the Ce atom at the FLP site is higher,which can transfer more electrons to the adsorbed C_(C=C)and O_(C=O)atoms,leading to a higher degree of activation for C=C and C=O bonds,as indicated by the Bader charge analysis.Therefore,compared to the CLP site,the FLP site exhibits higher hydrogenation activity for CH_(2)=CH_(2)and CH_(3)CH=O.Furthermore,at the FLP sites,it demonstrates high efficiency in catalyzing the hydrogenation of CH_(2)=CH_(2)with the rate-determining barrier of 1.04 eV,but it shows limited activity for the hydrogenation of CH_(3)CH=O with the rate-determining barrier of 1.94 eV.It means that the selective hydrogenation of C=C can be effectively achieved at the FLP sites concerning selective hydrogenation catalysis.The insights shown in this work help to clarify the reaction mechanism of the hydrogenation of C=C and C=O at FLP site on CeO_(2)(110)and reveal the relationship between the catalytic performance and the nature of the active site,which is of great benefit to development of rational design of heterogeneous FLP catalysts.展开更多
基金supported by the National Natural Science Foundation of China(22172086,22105117)the Taishan Scholars Program of Shandong Province(202103064)the Major Basic Research Project of Shandong Province(ZR2021ZD06)。
文摘Lewis acid(LA)and Lewis base(LB)sites on catalyst surfaces play a pivotal role in catalytic reactions.By precisely modulating the type,density,and spatial distribution of these Lewis acid/base sites,catalytic performance indicators such as catalytic activity,selectivity,and stability can be effectively optimized.As a result,they become essential parameters that must be considered in the design and development of high-efficiency catalysts.This study proposes a surface engineering method to accurately control the concentration of surface LA and LB sites in defect-laden In_(2)O_(3-x)(OH)_(y)(denoted as N-n%-IO),establishing three types of LB/LA stoichiometric ratios with different photocatalytic CO_(2)hydrogenation performances.It is demonstrated that the LB-rich system(LB/LA>1)shows suppressed activity.In contrast,the balanced stoichiometric ratio system(LB/LA=1)attains an optimal methanol yield(179.79μmol g^(-1)h^(-1))and selectivity(43.67%),while the LA-rich system(LB/LA<1)exhibits the best CO production rate(1913.76μmol g^(-1)h^(-1))and selectivity(94.96%).Systematic experiments disclose that the balanced LB/LA system with adjacent surface frustrated Lewis pairs(SFLPs)can effectively facilitate the adsorption/activation of reactants,stabilize intermediates,and regulate the dynamic behavior of photo-generated carriers.However,the imbalanced LB/LA systems either lack necessary active sites or can only follow an oxygen vacancy-mediated pathway during photocatalytic CO_(2)hydrogenation.This work offers a comprehensive understanding of the crucial functions of surface Lewis acid/base sites in the product distribution of solar-driven CO_(2)reduction.
基金supported by the National Natural Science Foundation of China (NSFC,Nos.12474274,92161101)the Innovation Project of Jinan Science and Technology Bureau (No.2021GXRC032)the Natural Science Foundation of Shandong Province (No.ZR2024MA091)。
文摘The Jellium closed-shell model,a cornerstone of cluster science,has long guided the design of superatoms by dictating electron-counting rules.However,its reliance on precise control of cluster composition and electron shell occupancy presents significant experimental challenges.Here,we introduce a ligation strategy that circumvents these limitations by demonstrating that the adiabatic electron affinity(AEA) of aluminum-based clusters,whether with filled or partially filled electron shells,can be dramatically enhanced through the attachment of organic Lewis acid ligands.It was evidenced that the AEA of PAl12can be significantly increased by 2.17 e V after the ligation of two ligands,indicating a remarkable improvement in its electron-accepting ability.This approach yields superhalogen species,offering a versatile and practical means to tune the electronic properties of clusters while preserving their superatomic states,independent of shell occupancy.Remarkably,this ligand-induced modulation is not confined to naked clusters but also extends to nano-confined systems,hinting at its broader applicability.Given the indispensable role of ligands in cluster synthesis,this strategy holds promise for advancing the field of condensed-phase superatom synthesis,potentially complementing traditional electron-counting rules in a broader range of applications.
基金funding from the National Natural Science Foundation of China (Award 91745203) supplemented by Central Universities’ Basic Research Funds.
文摘Ceramic cells promise ideal energy conversion and storage devices,making the development of efficient and robust air electrodes crucial for their application.In this study,a Ba_(0.4)Sr_(0.5)Cs_(0.1)Co_(0.7)Fe_(0.2)Nb_(0.1)O_(3−δ)(BSCCFN)air electrode,based on Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3−δ)(BSCF),is designed using a perovskite A-B-site ionic Lewis acid strength(ISA)polarization distribution strategy and is successfully applied in both oxygen-ion conducting solid oxide fuel cells(O-SOFCs)and proton-conducting reversible protonic ceramic cells(R-PCCs).When BSCCFN is used as the air electrode in O-SOFCs,a peak power density(PPD)of 1.45 W cm^(−2)is achieved at 650°C,whereas in R-PCCs,a PPD of 1.13 W cm^(−2)and a current density of−1.8 A cm^(−2)at 1.3 V are achieved at the same temperature and show stable reversibility over 100 h.Experimental measurements and theoretical calculations demonstrate that low-ISA Cs+doping accelerates the reaction kinetics of both oxygen ions and protons,while high-ISA Nb^(5+)doping enhances electrode stability.The synergistic effect of Cs^(+)and Nb^(5+)co-doping in the BSCCFN electrode lies in the ISA polarization distribution,which weakens the Co/Fe–O bond covalency,thereby promoting oxygen vacancy formation and facilitating the conduction of oxygen ions and protons.
基金Fundamental Research Foundation of CAF (CAFYBB2022QB001)National Nature Science Foundation of China for Excellent Young Scientists Fund (32222058)。
文摘The high-efficiency conversion of biomass resources to biofuels has attracted widespread attention, and the active sites and synergistic effect of catalysts significantly impact their surface arrangement and electronic structure. Here, a nickel-based transition metal carbide catalyst(Ni/TMC) with high Lewis acidity was prepared by self-assembly of transition metal carbide(TMC) and nickel, which exhibited excellent performance on synergistic hydrogenation and hydrogenolysis of 5-hydroxymethylfurfural(HMF) into liquid biofuel 2,5-dimethylfuran(DMF).Notably, Ni/WC with the highest Lewis acidity(4728.3 μmol g^(-1)) can achieve 100% conversion of HMF to 97.6% yield of DMF, with a turnover frequency of up to 46.5 h^(-1). The characterization results demonstrate that the rich Lewis acid sites yielded by the synergistic effect between Ni species and TMC are beneficial for the C=O hydrogenation and C–O cleavage, thereby accelerating the process of hydrodeoxygenation(HDO). Besides, a kinetic model for the HDO of HMF to DMF process has been established based on the experimental results, which elucidated a significant correlation between the measured and the predicted data(R^(2)> 0.97). Corresponding to the adsorption configuration of Ni/WC and substrate determined by in-situ FTIR characterization, this study provides a novel insight into the selective conversion of HMF process for functional biofuel and bio-chemicals.
基金supported by the National Natural Science Foundation of China(No.52201274)the Project of Education Department of Shanxi Province(No.22JK0419).
文摘High-capacity LiBH_(4)is a promising solid hydrogen storage material.However,the large electron cloud density between the B-H bonds in LiBH_(4)induces high dehydrogenation temperatures and sluggish dehydrogenation kinetics.To solve the above problems,it is proposed to enhance the hydrogen storage properties of LiBH_(4)through the synergistic effect of Brønsted and Lewis acid in Hβzeolite.Composite hydrogen storage systems with different mass ratios were prepared by simple ball-milling.At a LiBH_(4)-to-Hβmass ratio of 6:4,the 6LiBH_(4)-4Hβsystem released hydrogen at 190℃and achieved a hydrogen release capacity of 7.0 wt%H_(2)upon heating to 400℃.More importantly,the hydrogen release capacity of the system reached 6.02 wt%at 350℃under isothermal conditions after 100 min and 7.2 wt%at 400℃under isothermal conditions after 80 min,whereas the pristine LiBH_(4)only achieved 2.2 wt%.The improvement in hydrogen storage performance of the system was mainly attributed to two factors:(i)Lewis acid sites with acceptable electrons in the Hβweaken the electron density of B-H bonds in LiBH_(4),and(ii)the H+proton from the Brønsted acid sites and H−of LiBH_(4)undergo a H^(+)+H^(−)=H_(2)reaction.Theoretical calculations revealed that the Lewis and Brønsted acid sites in the Hβzeolite are conducive to the weakening of B-H bonds and that storage charge transfer occurs near the Lewis acid sites.The present work provides new insights into improving the hydrogen storage performance of LiBH_(4)by weakening the B-H bonds in the LiBH_(4).
基金supported by the USTC Research Funds of the Double First-Class Initiative(YD2060006004,YD2060002027)the National Natural Science Foundation of China(22325107,22171253,22293011).
文摘This study employs density functional theory(DFT)calculations to systematically investigate the B‒H bond dissociation enthalpies(BDEs)of Lewis base‒borane complexes.A rigorous benchmark analysis identified theωB97XD/cc-pVTZ method as a reliable method for accurate prediction of B–H BDEs.An examination of more than 200 structurally diverse complexes across five major classes revealed that the type of Lewis base significantly influences the BDEs,with the order of amine–borane>phosphine–borane>N-heterocyclic carbene–borane>pyridine–borane.Solventstabilized boranes exhibit the broadest range of BDE values due to the diverse coordination modes of solvent molecules with borane.Further analysis revealed that the BDE values are synergistically affected by skeletal and substituent effects.Notably,a strong linear correlation(R^(2) up to 0.97)between the spin density of boryl radicals and BDEs,except for amine–boranes,provides a robust predictive model.This research enhances the fundamental understanding of B‒H bond dissociation properties in Lewis base–boranes and provides valuable insights for the development of new boron-based methodologies in organic synthesis.
基金supported by the National Natural Science Foundation of China(22302115,22072079)the Fundamental Research Program of Shanxi Province(202303021221056).
文摘Heterogeneous solid frustrated-Lewis-pair(FLP)catalyst is of great promise in practical hydrogenation applications.It has been found that all-solid FLPs can be created on ceria via surface oxygen vacancy regulation.Consequently,it is desired to investigate the mechanisms of the FLP-catalyzed hydrogenation of C=C and C=O and provide insight into the modification of CeO_(2)catalysts for the selective hydrogenation.In this work,the reaction mechanism of the hydrogenation of CH_(2)=CH_(2)and CH_(3)CH=O at the FLP sites constructed on CeO_(2)(110)surface was investigated by density functional theory(DFT),with the classical Lewis acid-base pairs(CLP)site as the reference.The results illustrate that at the CLP site,the dissociated hydride(H^(δ−))forms a stable H−O bond with the surface O atom,while at the FLP site,H^(δ−)is stabilized by Ce,displaying higher activity on the one hand.On the other hand,the electron cloud density of the Ce atom at the FLP site is higher,which can transfer more electrons to the adsorbed C_(C=C)and O_(C=O)atoms,leading to a higher degree of activation for C=C and C=O bonds,as indicated by the Bader charge analysis.Therefore,compared to the CLP site,the FLP site exhibits higher hydrogenation activity for CH_(2)=CH_(2)and CH_(3)CH=O.Furthermore,at the FLP sites,it demonstrates high efficiency in catalyzing the hydrogenation of CH_(2)=CH_(2)with the rate-determining barrier of 1.04 eV,but it shows limited activity for the hydrogenation of CH_(3)CH=O with the rate-determining barrier of 1.94 eV.It means that the selective hydrogenation of C=C can be effectively achieved at the FLP sites concerning selective hydrogenation catalysis.The insights shown in this work help to clarify the reaction mechanism of the hydrogenation of C=C and C=O at FLP site on CeO_(2)(110)and reveal the relationship between the catalytic performance and the nature of the active site,which is of great benefit to development of rational design of heterogeneous FLP catalysts.
