Reduced graphene oxide(rGO)aerogels are emerging as very attractive scaffolds for high-performance electromagnetic wave absorption materials(EWAMs)due to their intrinsic conductive networks and intricate interior micr...Reduced graphene oxide(rGO)aerogels are emerging as very attractive scaffolds for high-performance electromagnetic wave absorption materials(EWAMs)due to their intrinsic conductive networks and intricate interior microstructure,as well as good compatibility with other electromagnetic(EM)components.Herein,we realized the decoration of rGO aerogel with Mo_(2)C nanoparticles by sequential hydrothermal assembly,freeze-drying,and high-temperature pyrolysis.Results show that Mo_(2)C nanoparticle loading can be easily controlled by the ammonium molybdate to glucose molar ratio.The hydrophobicity and thermal insulation of the rGO aerogel are effectively improved upon the introduction of Mo_(2)C nanoparticles,and more importantly,these nanoparticles regulate the EM properties of the rGO aerogel to a large extent.Although more Mo_(2)C nanoparticles may decrease the overall attenuation ability of the rGO aerogel,they bring much better impedance matching.At a molar ratio of 1:1,a desirable balance between attenuation ability and impedance matching is observed.In this context,the Mo_(2)C/r GO aerogel displays strong reflection loss and broad response bandwidth,even with a small applied thickness(1.7 mm)and low filler loading(9.0wt%).The positive effects of Mo_(2)C nanoparticles on multifunctional properties may render Mo_(2)C/r GO aerogels promising candidates for high-performance EWAMs under harsh conditions.展开更多
Microwave absorbing materials(MAMs)characterized by high absorption efficiency and good environmental tolerance are highly desirable in practical applications.Both silicon carbide and carbon are considered as stable M...Microwave absorbing materials(MAMs)characterized by high absorption efficiency and good environmental tolerance are highly desirable in practical applications.Both silicon carbide and carbon are considered as stable MAMs under some rigorous conditions,while their composites still fail to produce satisfactory microwave absorption performance regardless of the improvements as compared with the individuals.Herein,we have successfully implemented compositional and structural engineering to fabricate hollow Si C/C microspheres with controllable composition.The simultaneous modulation on dielectric properties and impedance matching can be easily achieved as the change in the composition of these composites.The formation of hollow structure not only favors lightweight feature,but also generates considerable contribution to microwave attenuation capacity.With the synergistic effect of composition and structure,the optimized SiC/C composite exhibits excellent performance,whose the strongest reflection loss intensity and broadest effective absorption reach-60.8 dB and 5.1 GHz,respectively,and its microwave absorption properties are actually superior to those of most SiC/C composites in previous studies.In addition,the stability tests of microwave absorption capacity after exposure to harsh conditions and Radar Cross Section simulation data demonstrate that hollow SiC/C microspheres from compositional and structural optimization have a bright prospect in practical applications.展开更多
Herein,we report bifunctional molybdenum-doped nickel sulfide on nickel foam(Mo-NiS_(x)/NF)for magnetic field-enhanced overall water splitting under alkaline conditions.Proper doping of Mo can lead to optimization of ...Herein,we report bifunctional molybdenum-doped nickel sulfide on nickel foam(Mo-NiS_(x)/NF)for magnetic field-enhanced overall water splitting under alkaline conditions.Proper doping of Mo can lead to optimization of the electronic structure of NiS_(x),which accelerates the dissociation of H2O and the adsorption of OH−in the hydrogen evolution reaction(HER)and the oxygen evolution reaction(OER)processes,respectively.In addition,the magnetically active Mo-NiS_(x)/NF can further enhance the HER and OER activity under an applied magnetic field due to the magnetoresistance effect and the ferromagnetic(FM)exchange-field penetration effect.As a result,Mo-NiS_(x)/NF requires low overpotentials of 307 mV at 50mA cm^(−2)(for OER)and 136 mV at 10mA cm^(−2)(for HER)under a magnetic field of 10000 G.Furthermore,the electrolytic cell constructed by the bifunctional Mo-NiS_(x)/NFs as both the cathode and the anode shows a low cell voltage of 1.594 V at 10 mA cm^(−2)with optimal stability over 60 h under the magnetic field.Simultaneous enhancement of the HER and OER processes by an external magnetic field through rational design of electrocatalysts might be promising for overall water splitting applications.展开更多
Magnetic carbon-based composites are the most attractive candidates for electromagnetic(EM)absorption because they can terminate the propagation of surplus EM waves in space by interacting with both electric and magne...Magnetic carbon-based composites are the most attractive candidates for electromagnetic(EM)absorption because they can terminate the propagation of surplus EM waves in space by interacting with both electric and magnetic branches.Metal-organic frameworks(MOFs)have demonstrated their great potential as sacrificing precursors of magnetic metals/carbon composites,because they provide a good platform to achieve high dispersion of magnetic nanoparticles in carbon matrix.Nevertheless,the chemical composition and microstructure of these composites are always highly dependent on their precursors and cannot promise an optimal EM state favorable for EM absorption,which more or less discount the superiority of MOFs-derived strategy.It is hence of great importance to develop some accompanied methods that can regulate EM properties of MOFs-derived magnetic carbon-based composites e ectively.This review comprehensively introduces recent advancements on EM absorption enhancement in MOFs-derived magnetic carbon-based composites and some available strategies therein.In addition,some challenges and prospects are also proposed to indicate the pending issues on performance breakthrough and mechanism exploration in the related field.展开更多
Carbides/carbon composites are emerging as a new kind of binary dielectric systems with good microwave absorption performance.Herein,we obtain a series of tungsten carbide/carbon composites through a simple solvent-fr...Carbides/carbon composites are emerging as a new kind of binary dielectric systems with good microwave absorption performance.Herein,we obtain a series of tungsten carbide/carbon composites through a simple solvent-free strategy,where the solid mixture of dicyandiamide(DCA)and ammonium metatungstate(AM)is employed as the precursor.Ultrafine cubic WC1-x nanoparticles(3-4 nm)are in situ generated and uniformly dispersed on carbon nanosheets.This configuration overcomes some disadvantages of conventional carbides/carbon composites and is greatly helpful for electromagnetic dissipation.It is found that the weight ratio of DCA to AM can regulate chemical composition of these composites,while less impact on the average size of WC1-x nanoparticles.With the increase in carbon nanosheets,the relative complex permittivity and dielectric loss ability are constantly enhanced through conductive loss and polarization relaxation.The different dielectric properties endow these composites with distinguishable attenuation ability and impedance matching.When DCA/AM weight ratio is 6.0,the optimized composite can produce good microwave absorption performance,whose strongest reflection loss intensity reaches up to-55.6 dB at 17.5 GHz and qualified absorption bandwidth covers 3.6-18.0 GHz by manipulating the thickness from 1.0 to 5.0 mm.Such a performance is superior to many conventional carbides/carbon composites.展开更多
Electromagnetic(EM)absorption is paving the way to overcome the challenges related to conventional shielding strategy against EM pollution through sustainable energy dissipation.As characteristic functional media that...Electromagnetic(EM)absorption is paving the way to overcome the challenges related to conventional shielding strategy against EM pollution through sustainable energy dissipation.As characteristic functional media that can interact with electric or magnetic field branch,EM wave absorption materials(EWAMs)have received extensive attention and realized considerable development in the past two decades,where carbon-based composites are always considered as promising candidates for high-performance EMAWs due to their synergetic loss mechanism as well as diversified composition and microstructure design.Recent progress indicates that there is more and more interest in the fabrication of carbon-based composites with unique core–shell configuration.On one hand,core–shell configuration usually ensures good chemical homogeneity of final products and provides some positive protections for the components with susceptibility to corrosion,on the other hand,it creates enough heterogeneous interfaces between different EM components,which may bring enhanced polarization effect and intensify the consumption of EM energy.In this review,we firstly introduce EM wave absorption theory,and then highlight the advances of core–shell engineering in carbonbased composites in terms of built-in carbon cores and built-out carbon shells.Moreover,we also show some special core–shell carbon-based composites,including carbon/carbon composites,assembled composites,and decorated composites.After analyzing EM absorption performance of some representative composites,we further propose some challenges and perspectives on the development of core–shell carbon-based composites.展开更多
Heteroatom-doped carbon nanomaterials have attracted significant attention as anode materials for sodium-ion batteries （SIBs）. Herein, we demonstrate a conjugated polymer-mediated synthesis of sulfur and nitrogen co...Heteroatom-doped carbon nanomaterials have attracted significant attention as anode materials for sodium-ion batteries （SIBs）. Herein, we demonstrate a conjugated polymer-mediated synthesis of sulfur and nitrogen co-doped carbon nanotubes （S/N-CT） via the carbonization of sulfur-containing polyaniline （PANI） nanotubes. It is found that the carbonization technique greatly influences the structural features and thus the Na-storage behavior of the S/N-CT materials. The carbon nanotubes developed using a two-step carbonization process （heating at 400℃ and then at 900℃） exhibit a high specific surface area, enlarged interlayer distance, small charge transfer resistance, enhanced reaction kinetics, as well as a large number of defects and active sites; further, they exhibit a high reversible capacity of 340 mAh·g^-1 at 0.1 A·g^-1 and a remarkable cycling stability with a capacity of 141 mAh·g^-1 at 5 A·g^-1 （94% retention after 3,000 cydes）. Direct carbonization of conjugated polymers with a specific morphology is an eco-friendly and low-cost technique for the synthesis of dual atom-doped carbon nanomaterials for application in energy devices. However, the carbonization process should be carefully controlled in order to better tune the structure-property relationship.展开更多
Constructing three-dimensional(3D)foam-like structure in magnetic metal/carbon composites is regarded as a promising pathway to reinforce their electromagnetic(EM)functions.Herein,a nitrateassisted polymer-bubbling st...Constructing three-dimensional(3D)foam-like structure in magnetic metal/carbon composites is regarded as a promising pathway to reinforce their electromagnetic(EM)functions.Herein,a nitrateassisted polymer-bubbling strategy is reported for the synthesis of Co/carbon foams,which is simply accomplished by direct pyrolyzing the mixture of polyvinylpyrrolidone(PVP)and cobalt nitrate hexahydrate(Co(NO_(3))_(2)·6 H_(2) O).Co(NO_(3))_(2)·6H_(2)O not only plays as the source of Co nanoparticles,but also accounts for the formation of 3D microstructure through releasing gas.By manipulating the weight ratio of Co(NO_(3))_(2)·6H_(2)O to PVP,the chemical composition,microstructure,and EM properties of these composites can be easily regulated.When the weight ratio reaches 1.5,the resultant composite displays good microwave absorption performance,whose reflection loss intensity and effective absorption bandwidth are superior to those of many common Co/C composites.EM analysis reveals that such architecture is greatly helpful to establish cross-linked conductive networks in the wax matrix,resulting in powerful dielectric loss under low absorber loading.Meanwhile,3D microstructure is also beneficial for multiple reflections that equal to extend the transmission path of incident EM waves.Simple synthesis strategy and desirable properties of these magnetic carbon foams may render them as the low-cost substitute of 3D graphene for the application against EM pollution.展开更多
基金supported by the China Postdoctoral Science Foundation(No.2021MD703944)the Fund of Science and Technology on Near-Surface Detection Laboratory(No.6142414211808)+1 种基金the Director Fund of State Key Laboratory of Pulsed Power Laser Technology(No.SKL2021ZR06)the National Natural Science Foundation of China(No.21776053)。
文摘Reduced graphene oxide(rGO)aerogels are emerging as very attractive scaffolds for high-performance electromagnetic wave absorption materials(EWAMs)due to their intrinsic conductive networks and intricate interior microstructure,as well as good compatibility with other electromagnetic(EM)components.Herein,we realized the decoration of rGO aerogel with Mo_(2)C nanoparticles by sequential hydrothermal assembly,freeze-drying,and high-temperature pyrolysis.Results show that Mo_(2)C nanoparticle loading can be easily controlled by the ammonium molybdate to glucose molar ratio.The hydrophobicity and thermal insulation of the rGO aerogel are effectively improved upon the introduction of Mo_(2)C nanoparticles,and more importantly,these nanoparticles regulate the EM properties of the rGO aerogel to a large extent.Although more Mo_(2)C nanoparticles may decrease the overall attenuation ability of the rGO aerogel,they bring much better impedance matching.At a molar ratio of 1:1,a desirable balance between attenuation ability and impedance matching is observed.In this context,the Mo_(2)C/r GO aerogel displays strong reflection loss and broad response bandwidth,even with a small applied thickness(1.7 mm)and low filler loading(9.0wt%).The positive effects of Mo_(2)C nanoparticles on multifunctional properties may render Mo_(2)C/r GO aerogels promising candidates for high-performance EWAMs under harsh conditions.
基金supported by the National Natural Science Foundation of China(No.21676065 and No.52373262)China Postdoctoral Science Foundation(2021MD703944,2022T150782).
文摘Microwave absorbing materials(MAMs)characterized by high absorption efficiency and good environmental tolerance are highly desirable in practical applications.Both silicon carbide and carbon are considered as stable MAMs under some rigorous conditions,while their composites still fail to produce satisfactory microwave absorption performance regardless of the improvements as compared with the individuals.Herein,we have successfully implemented compositional and structural engineering to fabricate hollow Si C/C microspheres with controllable composition.The simultaneous modulation on dielectric properties and impedance matching can be easily achieved as the change in the composition of these composites.The formation of hollow structure not only favors lightweight feature,but also generates considerable contribution to microwave attenuation capacity.With the synergistic effect of composition and structure,the optimized SiC/C composite exhibits excellent performance,whose the strongest reflection loss intensity and broadest effective absorption reach-60.8 dB and 5.1 GHz,respectively,and its microwave absorption properties are actually superior to those of most SiC/C composites in previous studies.In addition,the stability tests of microwave absorption capacity after exposure to harsh conditions and Radar Cross Section simulation data demonstrate that hollow SiC/C microspheres from compositional and structural optimization have a bright prospect in practical applications.
基金National Natural Science Foundation of China,Grant/Award Numbers:21871065,22071038Heilongjiang Touyan Team,Grant/Award Number:HITTY‐20190033Interdisciplinary Research Foundation of HIT,Grant/Award Number:IR2021205。
文摘Herein,we report bifunctional molybdenum-doped nickel sulfide on nickel foam(Mo-NiS_(x)/NF)for magnetic field-enhanced overall water splitting under alkaline conditions.Proper doping of Mo can lead to optimization of the electronic structure of NiS_(x),which accelerates the dissociation of H2O and the adsorption of OH−in the hydrogen evolution reaction(HER)and the oxygen evolution reaction(OER)processes,respectively.In addition,the magnetically active Mo-NiS_(x)/NF can further enhance the HER and OER activity under an applied magnetic field due to the magnetoresistance effect and the ferromagnetic(FM)exchange-field penetration effect.As a result,Mo-NiS_(x)/NF requires low overpotentials of 307 mV at 50mA cm^(−2)(for OER)and 136 mV at 10mA cm^(−2)(for HER)under a magnetic field of 10000 G.Furthermore,the electrolytic cell constructed by the bifunctional Mo-NiS_(x)/NFs as both the cathode and the anode shows a low cell voltage of 1.594 V at 10 mA cm^(−2)with optimal stability over 60 h under the magnetic field.Simultaneous enhancement of the HER and OER processes by an external magnetic field through rational design of electrocatalysts might be promising for overall water splitting applications.
基金supported by the financial support from Natural Science Foundation of China(21776053 and 21676065)。
文摘Magnetic carbon-based composites are the most attractive candidates for electromagnetic(EM)absorption because they can terminate the propagation of surplus EM waves in space by interacting with both electric and magnetic branches.Metal-organic frameworks(MOFs)have demonstrated their great potential as sacrificing precursors of magnetic metals/carbon composites,because they provide a good platform to achieve high dispersion of magnetic nanoparticles in carbon matrix.Nevertheless,the chemical composition and microstructure of these composites are always highly dependent on their precursors and cannot promise an optimal EM state favorable for EM absorption,which more or less discount the superiority of MOFs-derived strategy.It is hence of great importance to develop some accompanied methods that can regulate EM properties of MOFs-derived magnetic carbon-based composites e ectively.This review comprehensively introduces recent advancements on EM absorption enhancement in MOFs-derived magnetic carbon-based composites and some available strategies therein.In addition,some challenges and prospects are also proposed to indicate the pending issues on performance breakthrough and mechanism exploration in the related field.
基金supported by National Natural Science Foundation of China(21676065 and 21776053)。
文摘Carbides/carbon composites are emerging as a new kind of binary dielectric systems with good microwave absorption performance.Herein,we obtain a series of tungsten carbide/carbon composites through a simple solvent-free strategy,where the solid mixture of dicyandiamide(DCA)and ammonium metatungstate(AM)is employed as the precursor.Ultrafine cubic WC1-x nanoparticles(3-4 nm)are in situ generated and uniformly dispersed on carbon nanosheets.This configuration overcomes some disadvantages of conventional carbides/carbon composites and is greatly helpful for electromagnetic dissipation.It is found that the weight ratio of DCA to AM can regulate chemical composition of these composites,while less impact on the average size of WC1-x nanoparticles.With the increase in carbon nanosheets,the relative complex permittivity and dielectric loss ability are constantly enhanced through conductive loss and polarization relaxation.The different dielectric properties endow these composites with distinguishable attenuation ability and impedance matching.When DCA/AM weight ratio is 6.0,the optimized composite can produce good microwave absorption performance,whose strongest reflection loss intensity reaches up to-55.6 dB at 17.5 GHz and qualified absorption bandwidth covers 3.6-18.0 GHz by manipulating the thickness from 1.0 to 5.0 mm.Such a performance is superior to many conventional carbides/carbon composites.
基金supported by the National Natural Science Foundation of China(No.21676065).
文摘Electromagnetic(EM)absorption is paving the way to overcome the challenges related to conventional shielding strategy against EM pollution through sustainable energy dissipation.As characteristic functional media that can interact with electric or magnetic field branch,EM wave absorption materials(EWAMs)have received extensive attention and realized considerable development in the past two decades,where carbon-based composites are always considered as promising candidates for high-performance EMAWs due to their synergetic loss mechanism as well as diversified composition and microstructure design.Recent progress indicates that there is more and more interest in the fabrication of carbon-based composites with unique core–shell configuration.On one hand,core–shell configuration usually ensures good chemical homogeneity of final products and provides some positive protections for the components with susceptibility to corrosion,on the other hand,it creates enough heterogeneous interfaces between different EM components,which may bring enhanced polarization effect and intensify the consumption of EM energy.In this review,we firstly introduce EM wave absorption theory,and then highlight the advances of core–shell engineering in carbonbased composites in terms of built-in carbon cores and built-out carbon shells.Moreover,we also show some special core–shell carbon-based composites,including carbon/carbon composites,assembled composites,and decorated composites.After analyzing EM absorption performance of some representative composites,we further propose some challenges and perspectives on the development of core–shell carbon-based composites.
基金We thank the financial support from National Natural Science Foundation of China （Nos. 21471039, 21571043, and 21671047）, Fundamental Research Funds for the Central Universities （PIRS of HIT A201502 and HIT. BRETⅢ. 201223）, China Postdoctoral Science Foundation （No. 2014M560253）, Postdoctoral Scientific Research Fund of Heilongjiang Province （Nos. LBH-Q14062 and LBH-Z14076）, Natural Science Foundation of Heilongjiang Province （No. B2015001）, and Youth Innovation Promotion Association of CAS （No. 2015316）.
文摘Heteroatom-doped carbon nanomaterials have attracted significant attention as anode materials for sodium-ion batteries （SIBs）. Herein, we demonstrate a conjugated polymer-mediated synthesis of sulfur and nitrogen co-doped carbon nanotubes （S/N-CT） via the carbonization of sulfur-containing polyaniline （PANI） nanotubes. It is found that the carbonization technique greatly influences the structural features and thus the Na-storage behavior of the S/N-CT materials. The carbon nanotubes developed using a two-step carbonization process （heating at 400℃ and then at 900℃） exhibit a high specific surface area, enlarged interlayer distance, small charge transfer resistance, enhanced reaction kinetics, as well as a large number of defects and active sites; further, they exhibit a high reversible capacity of 340 mAh·g^-1 at 0.1 A·g^-1 and a remarkable cycling stability with a capacity of 141 mAh·g^-1 at 5 A·g^-1 （94% retention after 3,000 cydes）. Direct carbonization of conjugated polymers with a specific morphology is an eco-friendly and low-cost technique for the synthesis of dual atom-doped carbon nanomaterials for application in energy devices. However, the carbonization process should be carefully controlled in order to better tune the structure-property relationship.
基金financially supported by the National Natural Science Foundation of China(Nos.21676065,21776053)。
文摘Constructing three-dimensional(3D)foam-like structure in magnetic metal/carbon composites is regarded as a promising pathway to reinforce their electromagnetic(EM)functions.Herein,a nitrateassisted polymer-bubbling strategy is reported for the synthesis of Co/carbon foams,which is simply accomplished by direct pyrolyzing the mixture of polyvinylpyrrolidone(PVP)and cobalt nitrate hexahydrate(Co(NO_(3))_(2)·6 H_(2) O).Co(NO_(3))_(2)·6H_(2)O not only plays as the source of Co nanoparticles,but also accounts for the formation of 3D microstructure through releasing gas.By manipulating the weight ratio of Co(NO_(3))_(2)·6H_(2)O to PVP,the chemical composition,microstructure,and EM properties of these composites can be easily regulated.When the weight ratio reaches 1.5,the resultant composite displays good microwave absorption performance,whose reflection loss intensity and effective absorption bandwidth are superior to those of many common Co/C composites.EM analysis reveals that such architecture is greatly helpful to establish cross-linked conductive networks in the wax matrix,resulting in powerful dielectric loss under low absorber loading.Meanwhile,3D microstructure is also beneficial for multiple reflections that equal to extend the transmission path of incident EM waves.Simple synthesis strategy and desirable properties of these magnetic carbon foams may render them as the low-cost substitute of 3D graphene for the application against EM pollution.
