PVDF-based nanocomposites have gained significant focus in capacitors for their excellent dielectric strength, its multi-scale structural inhomogeneity is the bottleneck for improving the energy storage performance. H...PVDF-based nanocomposites have gained significant focus in capacitors for their excellent dielectric strength, its multi-scale structural inhomogeneity is the bottleneck for improving the energy storage performance. Here, the composite components are optimized by the matrix modification,BST(Ba_(0.6)Sr_(0.4)TiO_(3)) ceramic fibrillation and surface coating. A series of PVDF/polymethyl methacrylate/lysozyme@BST nanofibers with continuous gradient distribution(PF-M/m BST nf-g) are prepared by the concentration gradient-biaxial high-speed electrospinning. The finite element simulation and experiment results indicate that the continuous gradient structure is favorable for the microstructure and inhomogeneity of the electric field distribution, significantly increasing the breakdown strength(Eb) and the permittivity(εr), as well as effectively suppressing the interfacial injected charge and leakage current. As a result, the energy storage density(Ue) of 23.1 J/cm^(3)at 600 MV/m with the charge-discharge efficiency(η) of 71% is achieved compared to PF-M(5.6 J/cm^(3)@350 MV/m, 65%). The exciting energy storage performance based on the well-designed PF-M/m BST nf-g provides important information for the development and application of polymer nanocomposite dielectrics.展开更多
In this work,the Si@reduced graphene oxide/ZrO_(2)(Si@rGO/ZrO_(2))with the shelled structures is prepared for the high-capacity and stable lithium-ion batteries.The shelled structure not only significantly improves th...In this work,the Si@reduced graphene oxide/ZrO_(2)(Si@rGO/ZrO_(2))with the shelled structures is prepared for the high-capacity and stable lithium-ion batteries.The shelled structure not only significantly improves the electrical conductivity of the whole electrode,but also protects the inner Si nanoparticles(Si NPs)from rupturing and being damaged by undesired side reactions with the electrolyte.As a result,the Si@rGO/ZrO_(2) anode delivers high initial discharge capacity of 3046 mAh·g^(−1) at 1.0 A·g^(−1).After 100 cycles,it can be maintained at 613 mAh·g^(−1),which is much higher than that of either the pure Si NPs(31 mAh·g^(−1))or the Si@rGO(261 mAh·g^(−1)).Even at 2 A·g^(−1),it still provides superior specific capacity of 834 mAh·g^(−1),while the pure Si anode merely possesses the capacity of 41 mAh·g^(−1).Moreover,the density functional theory calculations point out that ZrO_(2) layer can effectively enhance the adsorption energy of Li+and optimize the migration paths of Li+,ensuring the electrochemical performance of Si@rGO/ZrO_(2) composite anode.Furthermore,the Li+storage mechanism and low volume expansion of Si@rGO/ZrO_(2) anode is investigated by ex-situ X-ray photoelectron spectroscopy and morphological evolution upon cycling,respectively.展开更多
Achieving devices that combine high energy density with exceptional rate capability remains a challenge in energy storage.In this study,we engineer a Sb/MXene interface with highly dispersed amorphous Sb atomic cluste...Achieving devices that combine high energy density with exceptional rate capability remains a challenge in energy storage.In this study,we engineer a Sb/MXene interface with highly dispersed amorphous Sb atomic clusters(ACs)on MXene surfaces(Sb_(ACs)/MXene).The strong interfacial interactions lead to charge redistribution,enhancing state densities at the Fermi level and increasing Li absorption energy.Moreover,the targeted material demonstrates high electrical conductivity,abundant electrochemical active sites,ultra-low charge transfer resistance and rapid reaction kinetics.As a result,when used as an anode for lithium-ion batteries,the optimized Sb_(ACs)/MXene electrode exhibits an excellent reversible capacity of 559.2 mAh g^(-1)at 0.1 A g^(-1)after 100 cycles,as well as the high-rate property and cycling stability(186.3 mAh g^(-1)at 1 A g^(-1)after 1000 cycles),which is almost twice higher than that of pure MXene electrode.Furthermore,it is determined that the amorphous Sb ACs undergo asymmetrical multi step reactions involving(de)alloying and conversion,further affirming the fast and stable performance of lithium storage.展开更多
Based on the data of land use status in 2009-2018 in the annual change survey results of Pu er City,Yunnan Province,China,the habitat quality in the city were studied by using InVEST models.The results show that the a...Based on the data of land use status in 2009-2018 in the annual change survey results of Pu er City,Yunnan Province,China,the habitat quality in the city were studied by using InVEST models.The results show that the area of cultivated land,construction land,and unused land in Pu er City continuously increased from 2009 to 2018.The growth rate of cultivated land and construction land in the next three years was significantly higher than that in the previous three years,while the area of gardens,grassland and woodland continuously decreased.From 2009 to 2018,the habitat quality in Pu er City showed a downward trend,that is,there was a clear increase in the proportion of moderate and poor habitat quality and a decrease in the proportion of superior and good habitat quality.Changes in habitat quality calculated by InVEST models can be used as a grasp of regional ecological environment in the investigation before the audit of natural resource assets and breakthroughs in finding clues of problems,thereby improving the scientificity and efficiency of audit work of natural resource assets.展开更多
The audit objectives,audit objects,time scope and regions,audit methods,evaluation content,evaluation indicator system and common problems in the audit of mineral resources are studied.The audit objectives of mineral ...The audit objectives,audit objects,time scope and regions,audit methods,evaluation content,evaluation indicator system and common problems in the audit of mineral resources are studied.The audit objectives of mineral resources assets are initially clarified,and the audit objects and scope are defined;common audit methods and audit contents are summarized,and the evaluation indicator system is constructed;common problems in practice are summarized to provide reference for the audit work of mineral resource assets of leading cadres.展开更多
Cost-effective,Pt-free catalysts possessing superior electrochemical activity and stability are highly desirable for triiodide reduction reaction in dye-sensitized solar cells(DSCs).Herein,CoSe_(2) nanoparticles embed...Cost-effective,Pt-free catalysts possessing superior electrochemical activity and stability are highly desirable for triiodide reduction reaction in dye-sensitized solar cells(DSCs).Herein,CoSe_(2) nanoparticles embedded in porous carbon shells(CoSe_(2)/CS)were explored as highly efficient catalysts toward triiodide reduction reaction.The CoSe_(2)/CS composites were fabricated using a soft-template approach involving the carbonization and selenization processes.The CoSe_(2) nanoparticles were well distributed within highly graphitized nitrogen-doped carbon nanoshells.More importantly,the CoSe_(2)/CS catalysts presented both high catalytic performance and long-term stability,outperforming those of the thermally-deposited Pt electrode.Furthermore,the optimized DSC device with a CoSe_(2)/CS catalyst-based counter electrode showed a power conversion efficiency of 7.54%,exceeding that of the thermally-deposited Pt(7.40%)counterpart.The enhanced catalytic activity,long-term stability and photovoltaic efficiency can be attributed to the much more reaction sites provided by CoSe_(2) nanoparticles embedded within the porous carbon shells,as well as the better band matching with the potential of the I_(3)^(−)/I^(−) redox couple,revealed by the Kelvin probe force microscope measurement.This work will provide a strategy to construct low-cost,highly efficient and stable non-Pt catalysts for photovoltaic applications.展开更多
Hierarchical Pt-alloys enriched with active sites are highly desirable for efficient catalysis,but their syntheses generally need time-consuming and elaborate annealing treatment at high temperature.We herein report a...Hierarchical Pt-alloys enriched with active sites are highly desirable for efficient catalysis,but their syntheses generally need time-consuming and elaborate annealing treatment at high temperature.We herein report a surface active-site engineering strategy for constructing the hierarchical PtNi nanocatalysts with an atomic Pt-skin layer(PtNi@Pt-SL)towards efficient triiodide reduction reaction(TRR)via an acid-dealloying approach.The facile acid-dealloying process promotes the formation of surface Pt active sites on the hierarchical Pt-alloys,and thus results in good catalytic performance towards TRR.Theoretical calculation reveals that the enhanced catalytic property stems from the moderate energy barriers for iodide atoms on the surface Pt active-sites.The surface active-site engineering strategy paves a new way for the design of active and durable electrocatalysts.展开更多
基金the support and funding from the National Natural Science Foundation of China (Nos. 51773164, 5186020071)Ningxia Natural Science Foundation (No. 2023AAC03104)。
文摘PVDF-based nanocomposites have gained significant focus in capacitors for their excellent dielectric strength, its multi-scale structural inhomogeneity is the bottleneck for improving the energy storage performance. Here, the composite components are optimized by the matrix modification,BST(Ba_(0.6)Sr_(0.4)TiO_(3)) ceramic fibrillation and surface coating. A series of PVDF/polymethyl methacrylate/lysozyme@BST nanofibers with continuous gradient distribution(PF-M/m BST nf-g) are prepared by the concentration gradient-biaxial high-speed electrospinning. The finite element simulation and experiment results indicate that the continuous gradient structure is favorable for the microstructure and inhomogeneity of the electric field distribution, significantly increasing the breakdown strength(Eb) and the permittivity(εr), as well as effectively suppressing the interfacial injected charge and leakage current. As a result, the energy storage density(Ue) of 23.1 J/cm^(3)at 600 MV/m with the charge-discharge efficiency(η) of 71% is achieved compared to PF-M(5.6 J/cm^(3)@350 MV/m, 65%). The exciting energy storage performance based on the well-designed PF-M/m BST nf-g provides important information for the development and application of polymer nanocomposite dielectrics.
基金supported by the Natural Science Foundation of Ningxia(No.2022AAC05014).
文摘In this work,the Si@reduced graphene oxide/ZrO_(2)(Si@rGO/ZrO_(2))with the shelled structures is prepared for the high-capacity and stable lithium-ion batteries.The shelled structure not only significantly improves the electrical conductivity of the whole electrode,but also protects the inner Si nanoparticles(Si NPs)from rupturing and being damaged by undesired side reactions with the electrolyte.As a result,the Si@rGO/ZrO_(2) anode delivers high initial discharge capacity of 3046 mAh·g^(−1) at 1.0 A·g^(−1).After 100 cycles,it can be maintained at 613 mAh·g^(−1),which is much higher than that of either the pure Si NPs(31 mAh·g^(−1))or the Si@rGO(261 mAh·g^(−1)).Even at 2 A·g^(−1),it still provides superior specific capacity of 834 mAh·g^(−1),while the pure Si anode merely possesses the capacity of 41 mAh·g^(−1).Moreover,the density functional theory calculations point out that ZrO_(2) layer can effectively enhance the adsorption energy of Li+and optimize the migration paths of Li+,ensuring the electrochemical performance of Si@rGO/ZrO_(2) composite anode.Furthermore,the Li+storage mechanism and low volume expansion of Si@rGO/ZrO_(2) anode is investigated by ex-situ X-ray photoelectron spectroscopy and morphological evolution upon cycling,respectively.
基金financially supported by the Project of Ningxia Natural Science Foundation(No.2024AAC05004)Ningxia Key R&D Plan(No.2023BSB03071)+1 种基金the Leading Talents Program of Science and Technology Innovation in Ningxia(No.2023GKLRLX11)the support from Seventh Group Youth Science and Technology Talents Project of Ningxia
文摘Achieving devices that combine high energy density with exceptional rate capability remains a challenge in energy storage.In this study,we engineer a Sb/MXene interface with highly dispersed amorphous Sb atomic clusters(ACs)on MXene surfaces(Sb_(ACs)/MXene).The strong interfacial interactions lead to charge redistribution,enhancing state densities at the Fermi level and increasing Li absorption energy.Moreover,the targeted material demonstrates high electrical conductivity,abundant electrochemical active sites,ultra-low charge transfer resistance and rapid reaction kinetics.As a result,when used as an anode for lithium-ion batteries,the optimized Sb_(ACs)/MXene electrode exhibits an excellent reversible capacity of 559.2 mAh g^(-1)at 0.1 A g^(-1)after 100 cycles,as well as the high-rate property and cycling stability(186.3 mAh g^(-1)at 1 A g^(-1)after 1000 cycles),which is almost twice higher than that of pure MXene electrode.Furthermore,it is determined that the amorphous Sb ACs undergo asymmetrical multi step reactions involving(de)alloying and conversion,further affirming the fast and stable performance of lithium storage.
基金Major Scientific and Technological Planning Project of Yunnan Province,China(2019ZE006).
文摘Based on the data of land use status in 2009-2018 in the annual change survey results of Pu er City,Yunnan Province,China,the habitat quality in the city were studied by using InVEST models.The results show that the area of cultivated land,construction land,and unused land in Pu er City continuously increased from 2009 to 2018.The growth rate of cultivated land and construction land in the next three years was significantly higher than that in the previous three years,while the area of gardens,grassland and woodland continuously decreased.From 2009 to 2018,the habitat quality in Pu er City showed a downward trend,that is,there was a clear increase in the proportion of moderate and poor habitat quality and a decrease in the proportion of superior and good habitat quality.Changes in habitat quality calculated by InVEST models can be used as a grasp of regional ecological environment in the investigation before the audit of natural resource assets and breakthroughs in finding clues of problems,thereby improving the scientificity and efficiency of audit work of natural resource assets.
文摘The audit objectives,audit objects,time scope and regions,audit methods,evaluation content,evaluation indicator system and common problems in the audit of mineral resources are studied.The audit objectives of mineral resources assets are initially clarified,and the audit objects and scope are defined;common audit methods and audit contents are summarized,and the evaluation indicator system is constructed;common problems in practice are summarized to provide reference for the audit work of mineral resource assets of leading cadres.
基金supported by The National Key Research and Development Program of China(No.2017YFF0205403)the National Natural Science Foundation of China(Grant No.21771019,11604063 and 21622304)+1 种基金the Fundamental Research Funds for the Central Universities(xk1901,buctrc201706,XK1802-6 and buctrc201919)support from the Public Hatching Platform for Recruited Talents of Beijing University of Chemical Technology.
文摘Cost-effective,Pt-free catalysts possessing superior electrochemical activity and stability are highly desirable for triiodide reduction reaction in dye-sensitized solar cells(DSCs).Herein,CoSe_(2) nanoparticles embedded in porous carbon shells(CoSe_(2)/CS)were explored as highly efficient catalysts toward triiodide reduction reaction.The CoSe_(2)/CS composites were fabricated using a soft-template approach involving the carbonization and selenization processes.The CoSe_(2) nanoparticles were well distributed within highly graphitized nitrogen-doped carbon nanoshells.More importantly,the CoSe_(2)/CS catalysts presented both high catalytic performance and long-term stability,outperforming those of the thermally-deposited Pt electrode.Furthermore,the optimized DSC device with a CoSe_(2)/CS catalyst-based counter electrode showed a power conversion efficiency of 7.54%,exceeding that of the thermally-deposited Pt(7.40%)counterpart.The enhanced catalytic activity,long-term stability and photovoltaic efficiency can be attributed to the much more reaction sites provided by CoSe_(2) nanoparticles embedded within the porous carbon shells,as well as the better band matching with the potential of the I_(3)^(−)/I^(−) redox couple,revealed by the Kelvin probe force microscope measurement.This work will provide a strategy to construct low-cost,highly efficient and stable non-Pt catalysts for photovoltaic applications.
基金The research was financially supported by the National Natural Science Foundation of China(No.21771019)the National Key Research and Development Program of China(No.2018YFA0702002)+1 种基金the Fundamental Research Funds for the Central Universities(Nos.XK1901 and buctrc202023)P.Ma is funded by China Postdoctoral Science Foundation(No.2020M672772)。
文摘Hierarchical Pt-alloys enriched with active sites are highly desirable for efficient catalysis,but their syntheses generally need time-consuming and elaborate annealing treatment at high temperature.We herein report a surface active-site engineering strategy for constructing the hierarchical PtNi nanocatalysts with an atomic Pt-skin layer(PtNi@Pt-SL)towards efficient triiodide reduction reaction(TRR)via an acid-dealloying approach.The facile acid-dealloying process promotes the formation of surface Pt active sites on the hierarchical Pt-alloys,and thus results in good catalytic performance towards TRR.Theoretical calculation reveals that the enhanced catalytic property stems from the moderate energy barriers for iodide atoms on the surface Pt active-sites.The surface active-site engineering strategy paves a new way for the design of active and durable electrocatalysts.
