An effective method is designed to construct three-dimensional(3D)Nb_(2)C/reduced graphene oxide(rGO)hybrid aerogels through a low-temperature graphene oxide(GO)-assisted hydrothermal self-assembly followed by freeze-...An effective method is designed to construct three-dimensional(3D)Nb_(2)C/reduced graphene oxide(rGO)hybrid aerogels through a low-temperature graphene oxide(GO)-assisted hydrothermal self-assembly followed by freeze-drying and annealing.The intimately coupled Nb_(2)C/rGO hybrid aerogel combines the advantages of large specific surface area and rich 3D interconnected porous structure of aerogel as well as high conductivity and low potassium diffusion energy barrier of Nb_(2)C,which not only effectively prevents the self-restacking of Nb2C nanosheets to allow more active sites exposed and accommodate the volume change during the charge/discharge process,but also increases the accessibility of electrolyte and promotes the rapid transfer of ions/electrons.As a result,Nb_(2)C/rGO-2 as the anode of potassium ion batteries(KIBs)delivers a large reversible specific capacity(301.7 mAh·g^(−1)after 500 cycles at 2.0 A·g^(−1)),an ultrahigh rate capability(155.5 mAh·g^(−1)at 20 A·g^(−1)),and an excellent long-term large-current cycle stability(198.8 mAh·g^(−1)after 1,000 cycles at 10 A·g^(−1),with a retention of 83.3%).Such a high-level electrochemical performance,especially the ultrahigh rate capability,is the best among transition metal carbides and nitride(MXene)-based materials reported so far for KIBs.The diffusion kinetics of K+is investigated thoroughly,and the synergetic charge–discharge mechanism and the structure–performance relationship of Nb_(2)C/rGO are revealed explicitly.The present work provides a good strategy to solve the self-restacking problem of two-dimensional materials and also enlarges the potential applications of MXenes.展开更多
Epoxy resin(EP)composites with satisfactory thermal and tribological performance are highly required for engineering moving components.However,the simple addition of fillers leaded to the serious filler agglomeration ...Epoxy resin(EP)composites with satisfactory thermal and tribological performance are highly required for engineering moving components.However,the simple addition of fillers leaded to the serious filler agglomeration and limited promotion in tribological properties.In this work,we constructed a new kind of three-dimensional(3D)reduced graphene oxide(RGO)/Si_(3)N_(4) hybrid aerogel for EP composites,which was prepared by a facile hydrothermal self-assembly method followed by freeze-drying technique.As a result,the dispersibility of Si_(3)N_(4) whiskers was greatly improved through wrapping of polydopamine–polyethyleneimine copolymer(PDA–PEI)copolymer and physical spacing of 3D skeleton.Furthermore,benefiting from the synergistic effect of RGO and Si_(3)N_(4)@PDA–PEI in the thermal network,the thermal conductivity of RGO/Si_(3)N_(4) hybrid aerogel(GSiA)–EP increased by 45.4%compared to that of the neat EP.In addition,the friction coefficient and wear rate of GSiA–EP decreased by 83.7%and 35.8%,respectively.This work is significant for opening a tribological performance enhancement strategy though constructing 3D hybrid architecture.展开更多
基金the National Natural Science Foundation of China(No.21773116)and Modern Analysis Center of Nanjing University.
文摘An effective method is designed to construct three-dimensional(3D)Nb_(2)C/reduced graphene oxide(rGO)hybrid aerogels through a low-temperature graphene oxide(GO)-assisted hydrothermal self-assembly followed by freeze-drying and annealing.The intimately coupled Nb_(2)C/rGO hybrid aerogel combines the advantages of large specific surface area and rich 3D interconnected porous structure of aerogel as well as high conductivity and low potassium diffusion energy barrier of Nb_(2)C,which not only effectively prevents the self-restacking of Nb2C nanosheets to allow more active sites exposed and accommodate the volume change during the charge/discharge process,but also increases the accessibility of electrolyte and promotes the rapid transfer of ions/electrons.As a result,Nb_(2)C/rGO-2 as the anode of potassium ion batteries(KIBs)delivers a large reversible specific capacity(301.7 mAh·g^(−1)after 500 cycles at 2.0 A·g^(−1)),an ultrahigh rate capability(155.5 mAh·g^(−1)at 20 A·g^(−1)),and an excellent long-term large-current cycle stability(198.8 mAh·g^(−1)after 1,000 cycles at 10 A·g^(−1),with a retention of 83.3%).Such a high-level electrochemical performance,especially the ultrahigh rate capability,is the best among transition metal carbides and nitride(MXene)-based materials reported so far for KIBs.The diffusion kinetics of K+is investigated thoroughly,and the synergetic charge–discharge mechanism and the structure–performance relationship of Nb_(2)C/rGO are revealed explicitly.The present work provides a good strategy to solve the self-restacking problem of two-dimensional materials and also enlarges the potential applications of MXenes.
基金The authors gratefully acknowledge the financial support from the National Natural Science Foundation of China(Grant No.52005487)Natural Science Foundation of Gansu Province(Grant No.20JR10RA057).
文摘Epoxy resin(EP)composites with satisfactory thermal and tribological performance are highly required for engineering moving components.However,the simple addition of fillers leaded to the serious filler agglomeration and limited promotion in tribological properties.In this work,we constructed a new kind of three-dimensional(3D)reduced graphene oxide(RGO)/Si_(3)N_(4) hybrid aerogel for EP composites,which was prepared by a facile hydrothermal self-assembly method followed by freeze-drying technique.As a result,the dispersibility of Si_(3)N_(4) whiskers was greatly improved through wrapping of polydopamine–polyethyleneimine copolymer(PDA–PEI)copolymer and physical spacing of 3D skeleton.Furthermore,benefiting from the synergistic effect of RGO and Si_(3)N_(4)@PDA–PEI in the thermal network,the thermal conductivity of RGO/Si_(3)N_(4) hybrid aerogel(GSiA)–EP increased by 45.4%compared to that of the neat EP.In addition,the friction coefficient and wear rate of GSiA–EP decreased by 83.7%and 35.8%,respectively.This work is significant for opening a tribological performance enhancement strategy though constructing 3D hybrid architecture.
基金National Natural Science Foundation of China(50872033,U1332107,U1532105)Fund of Key Laboratory of Carbon Materials,Chinese Academy of Sciences(KFJJ0903)+2 种基金the Capacity Building Program of Shanghai Local Universities(12160503600)First-class Discipline Construction Fund of Shanghai Municipal Education Commission(J201212)Key Discipline Construction Fund of Composite Materials of Shanghai Institute of Technology(10210Q150001)~~
