The rich porous structure,high surface area and surface doping make nitrogen doping mesoporous carbon materials(N-MPC)attractive in various areas,including adsorption separation,electrochemical energy storage,catalysi...The rich porous structure,high surface area and surface doping make nitrogen doping mesoporous carbon materials(N-MPC)attractive in various areas,including adsorption separation,electrochemical energy storage,catalysis and other fields.Herein,polyvinylpyrrolidone(PVP)is introduced into the polymerization process of assembly of phenol/formaldehyde(PF)resin by means of hydrogen bonds and electrostatic interaction,which not only leads to the formation of uniform mesopores,but also leads to the increase of specific surface area and nitrogen doping.The amount of PVP and annealing temperature has no obvious effect on morphology,but subsequently has effect on the specific surface area and pore volume.When appropriate PVP dosage and annealing temperature are adopted,the obtained N-MPC shows abundant mesoporous,high surface area and suitable nitrogen doping.As electrode materials in supercapacitor,the N-MPC shows good performance with high capacitance good stability and rate performance,presenting its excellent promising in energy storage.展开更多
To address the severe electromagnetic(EM)pollution and thermal exhaustion issues in modern electronics,C@Mn_(x)O_(y) foams were first reported as an advanced multifunctional filler with superior microwave absorption,R...To address the severe electromagnetic(EM)pollution and thermal exhaustion issues in modern electronics,C@Mn_(x)O_(y) foams were first reported as an advanced multifunctional filler with superior microwave absorption,Radar wave stealth,and thermal dissipation.They were synthesized using a simple one-step annealing route,in which PVP and in-situ generated gas bubbles play a crucial role in the foam formation.Our results show that the C@Mn_(x)O_(y) foams possess excellent electrical insulation and a large thermal conductivity of 3.58 W(m K)^(–1) at a low load of 5 wt.%.Also,they exhibit prominent microwave absorption capabilities(MWACs)with a strong absorption(–46.03 dB)and a wide bandwidth(11.04 GHz)in a low load(30 wt.%).When they are then used as a patch,the wideband Radar cross-section can be effectively reduced by up to 41.34 dB m^(2).This performance outperforms most other heterostructures.Furthermore,the mechanism of dielectric loss and thermal transfer at the atomic level is revealed by the First-principle calculations of the density of states(DOS)and the phonon density of states(PDOS).The combination of C,MnO,and Mn_(3)O_(4) disrupts local microstructure symmetry and induces extra electrical dipoles at the heterointerfaces,benefiting the enhanced MWACs of C@Mn_(x)O_(y) foams along with defect polarization and multiple scattering.Their enhanced TC could be credited to the co-transmission of low phonon-boundary/phonon-defect scattering and multiple-frequency phonons from C,MnO,and Mn_(3)O_(4).Overall,the C@Mn_(x)O_(y) foams are highly promising for application in EM protection,absorption,and thermal management.What is more,this study provides a theoretical guide for designing heterostructures as effective microwave absorbing and thermally conductive materials used in modern electronics.展开更多
基金financially supported by the Beijing National Laboratory for Molecular Sciencesthe Hebei Province Introduction of Foreign Intelligence Projects(2018)the National Natural Science Foundation of China(No.21676070)。
文摘The rich porous structure,high surface area and surface doping make nitrogen doping mesoporous carbon materials(N-MPC)attractive in various areas,including adsorption separation,electrochemical energy storage,catalysis and other fields.Herein,polyvinylpyrrolidone(PVP)is introduced into the polymerization process of assembly of phenol/formaldehyde(PF)resin by means of hydrogen bonds and electrostatic interaction,which not only leads to the formation of uniform mesopores,but also leads to the increase of specific surface area and nitrogen doping.The amount of PVP and annealing temperature has no obvious effect on morphology,but subsequently has effect on the specific surface area and pore volume.When appropriate PVP dosage and annealing temperature are adopted,the obtained N-MPC shows abundant mesoporous,high surface area and suitable nitrogen doping.As electrode materials in supercapacitor,the N-MPC shows good performance with high capacitance good stability and rate performance,presenting its excellent promising in energy storage.
基金financially supported by the National Natural Science Foundation of China(No.52073260)the Zhejiang Provincial Natural Science Foundation of China(Nos.LGG21E020002 and LZ24E020004)the Major industrial projects of Jinhua City(No.2024A11011).
文摘To address the severe electromagnetic(EM)pollution and thermal exhaustion issues in modern electronics,C@Mn_(x)O_(y) foams were first reported as an advanced multifunctional filler with superior microwave absorption,Radar wave stealth,and thermal dissipation.They were synthesized using a simple one-step annealing route,in which PVP and in-situ generated gas bubbles play a crucial role in the foam formation.Our results show that the C@Mn_(x)O_(y) foams possess excellent electrical insulation and a large thermal conductivity of 3.58 W(m K)^(–1) at a low load of 5 wt.%.Also,they exhibit prominent microwave absorption capabilities(MWACs)with a strong absorption(–46.03 dB)and a wide bandwidth(11.04 GHz)in a low load(30 wt.%).When they are then used as a patch,the wideband Radar cross-section can be effectively reduced by up to 41.34 dB m^(2).This performance outperforms most other heterostructures.Furthermore,the mechanism of dielectric loss and thermal transfer at the atomic level is revealed by the First-principle calculations of the density of states(DOS)and the phonon density of states(PDOS).The combination of C,MnO,and Mn_(3)O_(4) disrupts local microstructure symmetry and induces extra electrical dipoles at the heterointerfaces,benefiting the enhanced MWACs of C@Mn_(x)O_(y) foams along with defect polarization and multiple scattering.Their enhanced TC could be credited to the co-transmission of low phonon-boundary/phonon-defect scattering and multiple-frequency phonons from C,MnO,and Mn_(3)O_(4).Overall,the C@Mn_(x)O_(y) foams are highly promising for application in EM protection,absorption,and thermal management.What is more,this study provides a theoretical guide for designing heterostructures as effective microwave absorbing and thermally conductive materials used in modern electronics.
