Developing lightweight and broadband microwave absorbers for dealing with serious electromagnetic radiation pollution is a great challenge.Here,a novel Fe-Co/N-doped carbon/reduced graphene oxide(Fe-Co/NC/rGO)composit...Developing lightweight and broadband microwave absorbers for dealing with serious electromagnetic radiation pollution is a great challenge.Here,a novel Fe-Co/N-doped carbon/reduced graphene oxide(Fe-Co/NC/rGO)composite with hierarchically porous structure was designed and synthetized by in situ growth of Fe-doped Cobased metal organic frameworks(Co-MOF)on the sheets of porous cocoon-like rGO followed by calcination.The Fe-Co/NC composites are homogeneously distributed on the sheets of porous rGO.The Fe-Co/NC/rGO composite with multiple components(Fe/Co/NC/rGO)causes magnetic loss,dielectric loss,resistance loss,interfacial polarization,and good impedance matching.The hierarchically porous structure of the Fe-Co/NC/rGO enhances the multiple reflections and scattering of microwaves.Compared with the Co/NC and Fe-Co/NC,the hierarchically porous Fe-Co/NC/rGO composite exhibits much better microwave absorption performances due to the rational composition and porous structural design.Its minimum reflection loss(RLmin)reaches?43.26 dB at 11.28 GHz with a thickness of 2.5 mm,and the effective absorption frequency(RL≤?10 dB)is up to 9.12 GHz(8.88-18 GHz)with the same thickness of 2.5 mm.Moreover,the widest effective bandwidth of 9.29 GHz occurs at a thickness of 2.63 mm.This work provides a lightweight and broadband microwave absorbing material while offering a new idea to design excellent microwave absorbers with multicomponent and hierarchically porous structures.展开更多
Nitrate(NO_(3)^(-)),a nitrogen-containing pollutant,is prevalent in aqueous solutions,contributing to a range of environmental and health-related issues.The electrocatalytic reduction of NO_(3)^(-)holds promise as a s...Nitrate(NO_(3)^(-)),a nitrogen-containing pollutant,is prevalent in aqueous solutions,contributing to a range of environmental and health-related issues.The electrocatalytic reduction of NO_(3)^(-)holds promise as a sustainable approach to both eliminating NO_(3)^(-)and generating valuable ammonia(NH_(3)).Nevertheless,the reduction reaction of NO_(3)^(-)(NO_(3)^(-)RR),involving 8-electron transfer process,is intricate,necessitating highly efficient electrocatalysts to facilitate the conversion of NO_(3)^(-)to NH_(3).In this study,Fe-doped Co_(3)O_(4) nanowire strutted three-dimensional(3D)pinewood-derived carbon(Fe-Co_(3)O_(4)/PC)is proposed as a high-efficiency NO_(3)^(-)RR electrocatalyst for NH_(3) production.Operating within 0.1 M NaOH containing NO_(3)^(-),Fe-Co_(3)O_(4)/PC demonstrates exceptional performance,obtain an impressively large NH_(3) yield of 0.55 mmol·h^(-1)·cm^(-2) and an exceptionally high Faradaic efficiency of 96.5%at-0.5 V,superior to its Co_(3)O_(4)/PC counterpart(0.2 mmol·h^(-1)·cm^(-2),73.3%).Furthermore,the study delves into the reaction mechanism of Fe-Co_(3)O_(4) for NO_(3)^(-)RR through theoretical calculations.展开更多
One-port surface acoustic wave resonators(SAWRs) are fabricated on semi-insulating high-quality bulk GaN and GaN film substrates, respectively. The semi-insulating GaN substrates are grown by hydride vapor phase epita...One-port surface acoustic wave resonators(SAWRs) are fabricated on semi-insulating high-quality bulk GaN and GaN film substrates, respectively. The semi-insulating GaN substrates are grown by hydride vapor phase epitaxy(HVPE)and doped with Fe. The anisotropy of Rayleigh propagation and the electromechanical coupling coefficient in Fe-doped GaN are investigated. The difference in resonance frequency between the SAWs between [1120] GaN and [1100] GaN is about 0.25% for the Rayleigh propagation mode, which is smaller than that of non-intentionally doped GaN film(~1%)reported in the literature. The electromechanical coupling coefficient of Fe-doped GaN is about 3.03%, which is higher than that of non-intentionally doped GaN film. The one-port SAWR fabricated on an 8-μm Fe-doped GaN/sapphire substrate has a quality factor of 2050, and that fabricated on Fe-doped bulk GaN has a quality factor as high as 3650. All of our results indicate that high-quality bulk GaN is a very promising material for application in SAW devices.展开更多
NH_(3),derived from electrocatalytic nitrogen reduction reaction(NRR),is promising to satisfy the need of food production and serve as a carbon-free liquid energy carrier in the near future.Yet major challenges remain...NH_(3),derived from electrocatalytic nitrogen reduction reaction(NRR),is promising to satisfy the need of food production and serve as a carbon-free liquid energy carrier in the near future.Yet major challenges remain in enhancing NH_(3) yield rate and conversion efficiency of available electrocatalysts.This work achieved an ultrahigh electrocatalytic NH_(3)yield rate on the_(0.50)Fe-Bi_(2)W0_(6) catalyst by a facile Fe-doped strategy.Up to 289μg·h^(-1)·mg_(cat)^(-1) of NH_(3) formation rate was obtained at-0.75 V vs.RHE,which was reliably quantized by indophenol blue and ^(1)H NMR methods.The impressive result is an order of magnitude higher than that of the reported Fe-and Bi-based catalysts,even more superior than the result of single atom Ru catalyst.The key of the outstanding NRR behaviors on the_(0.50)Fe-Bi_(2)W0_(6) catalyst is the significant hydrogen evolution reaction(HER)suppression and the synergy between Bi and Fe,which can effectively modulate the electron distribution and accelerate the electron transport.This work endows a new insight to further explore the high-performance electrocatalysts toward NRR.展开更多
Nickel diselenide(NiSe_(2)),which has a high theoretical capacity,has attracted considerable attention as a promis-ing anode material for sodium-ion batteries(SIBs).Nevertheless,the intrinsically low conductivity,larg...Nickel diselenide(NiSe_(2)),which has a high theoretical capacity,has attracted considerable attention as a promis-ing anode material for sodium-ion batteries(SIBs).Nevertheless,the intrinsically low conductivity,large volume variation,and significant aggregation of NiSe_(2)during sodiation/desodiation remain significant obstacles to its application.Herein,we report flower-like Fe-doped NiSe_(2)/C hybrid spheres(denoted as Fe-NiSe_(2)/C)fabricated by a glucose intercalation strategy for efficient sodium storage.These Fe-NiSe_(2)/C hybrid spheres are composed of thin porous carbon nanosheets decorated with Fe-NiSe_(2)nanoparticles.In situ introduced carbon nanosheets derived from intercalated glucose accompanied by moderate Fe doping in NiSe2 nanoparticles can provide ac-celerated ion/electron transfer kinetics through fast ion channels in the flower-like architecture and intimately contacted interfaces between NiSe_(2)and carbon nanosheets as well as maintain structural integrity by alleviating volume variation.Consequently,the optimal anode of the Fe-NiSe_(2)/C hybrid spheres delivered a high discharge capacity of 415 mAh g^(-1)at 0.5 A g^(-1),outstanding rate capability(243 mAh g^(-1)at 5 A g^(-1)),and significantly enhanced cycling stability(388 mAh g^(-1)at 1 A g^(-1)over 200 cycles).This work offers an efficient and valu-able strategy for realizing tailored heteroatom doping in transition metal selenides,accompanied by an in situ combination of conductive carbonaceous networks for advanced alkali metal ion batteries.展开更多
基金the National Natural Science Foundation of China(No.21376029)and the Analysis&Testing Center,Beijing Institute of Technology for sponsoring this researchsupported by Beijing Key Laboratory for Chemical Power Source and Green Catalysis,Beijing Institute of Technology.
文摘Developing lightweight and broadband microwave absorbers for dealing with serious electromagnetic radiation pollution is a great challenge.Here,a novel Fe-Co/N-doped carbon/reduced graphene oxide(Fe-Co/NC/rGO)composite with hierarchically porous structure was designed and synthetized by in situ growth of Fe-doped Cobased metal organic frameworks(Co-MOF)on the sheets of porous cocoon-like rGO followed by calcination.The Fe-Co/NC composites are homogeneously distributed on the sheets of porous rGO.The Fe-Co/NC/rGO composite with multiple components(Fe/Co/NC/rGO)causes magnetic loss,dielectric loss,resistance loss,interfacial polarization,and good impedance matching.The hierarchically porous structure of the Fe-Co/NC/rGO enhances the multiple reflections and scattering of microwaves.Compared with the Co/NC and Fe-Co/NC,the hierarchically porous Fe-Co/NC/rGO composite exhibits much better microwave absorption performances due to the rational composition and porous structural design.Its minimum reflection loss(RLmin)reaches?43.26 dB at 11.28 GHz with a thickness of 2.5 mm,and the effective absorption frequency(RL≤?10 dB)is up to 9.12 GHz(8.88-18 GHz)with the same thickness of 2.5 mm.Moreover,the widest effective bandwidth of 9.29 GHz occurs at a thickness of 2.63 mm.This work provides a lightweight and broadband microwave absorbing material while offering a new idea to design excellent microwave absorbers with multicomponent and hierarchically porous structures.
文摘Nitrate(NO_(3)^(-)),a nitrogen-containing pollutant,is prevalent in aqueous solutions,contributing to a range of environmental and health-related issues.The electrocatalytic reduction of NO_(3)^(-)holds promise as a sustainable approach to both eliminating NO_(3)^(-)and generating valuable ammonia(NH_(3)).Nevertheless,the reduction reaction of NO_(3)^(-)(NO_(3)^(-)RR),involving 8-electron transfer process,is intricate,necessitating highly efficient electrocatalysts to facilitate the conversion of NO_(3)^(-)to NH_(3).In this study,Fe-doped Co_(3)O_(4) nanowire strutted three-dimensional(3D)pinewood-derived carbon(Fe-Co_(3)O_(4)/PC)is proposed as a high-efficiency NO_(3)^(-)RR electrocatalyst for NH_(3) production.Operating within 0.1 M NaOH containing NO_(3)^(-),Fe-Co_(3)O_(4)/PC demonstrates exceptional performance,obtain an impressively large NH_(3) yield of 0.55 mmol·h^(-1)·cm^(-2) and an exceptionally high Faradaic efficiency of 96.5%at-0.5 V,superior to its Co_(3)O_(4)/PC counterpart(0.2 mmol·h^(-1)·cm^(-2),73.3%).Furthermore,the study delves into the reaction mechanism of Fe-Co_(3)O_(4) for NO_(3)^(-)RR through theoretical calculations.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFB0403002)the National Science Fund for Distinguished Young Scholars,China(Grant No.Y3CHC11001)the National Natural Science Foundation of China(Grant No.11604368)
文摘One-port surface acoustic wave resonators(SAWRs) are fabricated on semi-insulating high-quality bulk GaN and GaN film substrates, respectively. The semi-insulating GaN substrates are grown by hydride vapor phase epitaxy(HVPE)and doped with Fe. The anisotropy of Rayleigh propagation and the electromechanical coupling coefficient in Fe-doped GaN are investigated. The difference in resonance frequency between the SAWs between [1120] GaN and [1100] GaN is about 0.25% for the Rayleigh propagation mode, which is smaller than that of non-intentionally doped GaN film(~1%)reported in the literature. The electromechanical coupling coefficient of Fe-doped GaN is about 3.03%, which is higher than that of non-intentionally doped GaN film. The one-port SAWR fabricated on an 8-μm Fe-doped GaN/sapphire substrate has a quality factor of 2050, and that fabricated on Fe-doped bulk GaN has a quality factor as high as 3650. All of our results indicate that high-quality bulk GaN is a very promising material for application in SAW devices.
基金supported by the National Natural Science Foundation of China(Nos.21675151,21705145 and 21721003)the Ministry of Science and Technology of China(No.2016YFA0203203).
文摘NH_(3),derived from electrocatalytic nitrogen reduction reaction(NRR),is promising to satisfy the need of food production and serve as a carbon-free liquid energy carrier in the near future.Yet major challenges remain in enhancing NH_(3) yield rate and conversion efficiency of available electrocatalysts.This work achieved an ultrahigh electrocatalytic NH_(3)yield rate on the_(0.50)Fe-Bi_(2)W0_(6) catalyst by a facile Fe-doped strategy.Up to 289μg·h^(-1)·mg_(cat)^(-1) of NH_(3) formation rate was obtained at-0.75 V vs.RHE,which was reliably quantized by indophenol blue and ^(1)H NMR methods.The impressive result is an order of magnitude higher than that of the reported Fe-and Bi-based catalysts,even more superior than the result of single atom Ru catalyst.The key of the outstanding NRR behaviors on the_(0.50)Fe-Bi_(2)W0_(6) catalyst is the significant hydrogen evolution reaction(HER)suppression and the synergy between Bi and Fe,which can effectively modulate the electron distribution and accelerate the electron transport.This work endows a new insight to further explore the high-performance electrocatalysts toward NRR.
基金the financial support provided by the Zhejiang Provincial Natural Science Foundation of China(Grant No.LY21E020010)National Natural Science Foundation of China(Grant No.52102315)+1 种基金Shanxi-Zheda Institute of Advanced Materials and Chemical Engineering(2021SZ-TD006)Science and Technology Program of Zhejiang University Institute of Wenzhou(Grant No.XMGLKJZX-202206).
文摘Nickel diselenide(NiSe_(2)),which has a high theoretical capacity,has attracted considerable attention as a promis-ing anode material for sodium-ion batteries(SIBs).Nevertheless,the intrinsically low conductivity,large volume variation,and significant aggregation of NiSe_(2)during sodiation/desodiation remain significant obstacles to its application.Herein,we report flower-like Fe-doped NiSe_(2)/C hybrid spheres(denoted as Fe-NiSe_(2)/C)fabricated by a glucose intercalation strategy for efficient sodium storage.These Fe-NiSe_(2)/C hybrid spheres are composed of thin porous carbon nanosheets decorated with Fe-NiSe_(2)nanoparticles.In situ introduced carbon nanosheets derived from intercalated glucose accompanied by moderate Fe doping in NiSe2 nanoparticles can provide ac-celerated ion/electron transfer kinetics through fast ion channels in the flower-like architecture and intimately contacted interfaces between NiSe_(2)and carbon nanosheets as well as maintain structural integrity by alleviating volume variation.Consequently,the optimal anode of the Fe-NiSe_(2)/C hybrid spheres delivered a high discharge capacity of 415 mAh g^(-1)at 0.5 A g^(-1),outstanding rate capability(243 mAh g^(-1)at 5 A g^(-1)),and significantly enhanced cycling stability(388 mAh g^(-1)at 1 A g^(-1)over 200 cycles).This work offers an efficient and valu-able strategy for realizing tailored heteroatom doping in transition metal selenides,accompanied by an in situ combination of conductive carbonaceous networks for advanced alkali metal ion batteries.
