Transition metal carbide/nitride cores within MXenes make them considerably useful for ultra-high-temperature reinforcement.However,extensive research on Ti_(3)C_(2)T_(x) MXene has revealed its tendency to undergo a p...Transition metal carbide/nitride cores within MXenes make them considerably useful for ultra-high-temperature reinforcement.However,extensive research on Ti_(3)C_(2)T_(x) MXene has revealed its tendency to undergo a phase transition to TiCy at temperatures above 800℃due to high activity of a superficial Ti atomic layer.Herein,spark plasma sintering of Ti_(3)C_(2)T_(x) and TiC is performed to prevent the Ti_(3)C_(2)T_(x) phase transition at temperatures up to 1900℃through the fabrication of composites at a pressure of 50 MPa.Using a focused ion beam scanning electron microscope to separate layered substances in the composites and examining selected area diffraction spots in a transmission electron microscope enabled identification of non-phase-transitioned MXene.First-principles calculations based on density functional theory indicated the formation of strong chemical bonding interfaces between Ti_(3)C_(2)T_(x) and TiC,which imposed a stability constraint on the Ti atomic layer at the Ti_(3)C_(2)T_(x) surface.Mechanical performance tests,such as three-point bending and fracture toughness analysis,demonstrated that the addition of Ti_(3)C_(2)T_(x) can effectively improve the cross-scale strengthening and toughening of the TiC matrix,providing a new path for designing and developing two-dimensional(2D)carbides cross-scale-enhanced three-dimensional(3D)carbides with the same elements relying on a wide variety of MXenes.展开更多
With the rapid development of new generations of miniaturized,integrated,and high-power electronic devices,it is particularly important to develop advanced composite materials with efficient thermal management capabil...With the rapid development of new generations of miniaturized,integrated,and high-power electronic devices,it is particularly important to develop advanced composite materials with efficient thermal management capability and excellent electromagnetic interference(EMI)shielding performance.Herein,an innovative biomass/MXene-derived conductive hybrid scaffold,cellulose nanocrystal(CNC)-konjac glucomannan(KGM)/MXene(CKM),was prepared by freeze-drying and thermal annealing,and then paraffin wax(PW)was encapsulated in CKM using vacuum impregnation method to obtain CNC-KGM/MXene@PW phase change composites(CKMPCCs).The results show that the obtained CKMPCCs possess considerable reusable stabilities,excellent EMI shielding properties,and thermal energy management capacities.Among them,the CKMPCC-6 with 2.3 wt.%MXene exhibits excellent solar-thermal and electro-thermal conversion capabilities.In addition,the EMI shielding effectiveness value is as high as 45.0 dB at 8.2–12.4 GHz and the corresponding melting enthalpy value is 215.7 J/g(relative enthalpy efficiency of 99.9%).In conclusion,the synthesized multifunctional phase change composites provide great potential for integrating outstanding EMI shielding and advanced thermal energy management applications.展开更多
Latent heat storage of phase change materials(PCMs)is expected to be a suitable method to enhance the absorption and conversion of solar energy because of their high heat storage density and excellent chemical stabili...Latent heat storage of phase change materials(PCMs)is expected to be a suitable method to enhance the absorption and conversion of solar energy because of their high heat storage density and excellent chemical stability.However,pure organic PCMs are limited by their low thermal conductivity,photothermal conversion,and thermal energy storage efficiency in practical applications.Herein,vertically oriented network composite PCMs are synthesized using reduced graphene oxide/MXene hybrid aerogels(r GO/MXene)as carrier materials and encapsulating stearic acid(SA)as the PCM.Because of the vertically aligned MXene and r GO hybridized backbones,the thermal conductivity of the composite reaches 1.21 W/(m K),which increases 317.24%,compared to SA.The melting enthalpy of composites reaches 168.25 J/g,which almost retains the melting enthalpy of pure SA.The addition of r GO and MXene significantly improves the photothermal conversion capability of composite PCMs(≤90.19%).Irradiating the oriented and non-oriented surfaces of the composite sample,it is found that the temperature rise is faster in the orientation direction than in the non-oriented direction,and the equilibrium temperature of the orientation direction is 4.8°C higher than that of the non-orientation direction.This new material has a high potential for use in solar energy storage applications because of its excellent performance.展开更多
MXene(M_(n+1)Xn)is an emerging class of layered two-dimensional(2D)materials,which are derived from their bulk-state MAX phase(M_(n+1)AXn,where M:early transition metal,A:group element 13 and 14,and X:carbon and/or ni...MXene(M_(n+1)Xn)is an emerging class of layered two-dimensional(2D)materials,which are derived from their bulk-state MAX phase(M_(n+1)AXn,where M:early transition metal,A:group element 13 and 14,and X:carbon and/or nitrogen).MXenes have found wide-ranging applications in energy storage devices,sensors,catalysis,etc.owing to their high electronic conductivity and wide range of optical absorption.However,the absence of semiconducting MXenes has limited their applications related to light emission.Research has shown that quantum dots(QDs)derived from MXene(MQDs)not only retain the properties of the parent MXene but also demonstrate significant improvement on light emission and quantum yield(QY).The optical properties and photoluminescence(PL)emission mechanisms of these light-emitting MQDs have not been comprehensively investigated.Recently,work on light-emitting MQDs has shown good progress,and MQDs exhibiting multi-color PL emission along with high QY have been fabricated.The synthesis methods also play a vital role in determining the light emission properties of these MQDs.This review provides an overview of light-emitting MQDs and their synthesis methods,optical properties,and applications in various optical,sensory,and imaging devices.The future prospects of light-emitting MQDs are also discussed to provide an insight that helps to further advance the progress on MQDs.展开更多
MXenes,a new class of 2D transition metal carbides,nitrides,and carbonitrides,have attracted much attention due to their outstanding properties.Here,we report the broadband spatial self-phase modulation of Ti2CTx MXen...MXenes,a new class of 2D transition metal carbides,nitrides,and carbonitrides,have attracted much attention due to their outstanding properties.Here,we report the broadband spatial self-phase modulation of Ti2CTx MXene nanosheets dispersed in deionized water in the visible to near-infrared regime,highlighting the broadband nonlinear optical(NLO)response of Ti2CTx MXene.Using ultrafast pulsed laser excitation,the nonlinear refractive index n2 and the thirdorder nonlinear susceptibility χ^(3)monolayer of Ti2CTx MXene were measured to be^10^−13 m^2/W and ~10^−10 esu,respectively.Leveraging the large optical nonlinearity of Ti2CTx MXene,an all-optical modulator in the visible regime was fabricated based on the spatial cross-phase modulation effect.This work suggests that 2D MXenes are ideal broadband NLO materials with excellent prospects in NLO applications.展开更多
Designing efficient electrocatalysts with low Pt loadings for hydrogen evolution reaction(HER)is urgently required for renewable and sustainable energy conversion.Here,we report a strategy that Pt nanoparticulates are...Designing efficient electrocatalysts with low Pt loadings for hydrogen evolution reaction(HER)is urgently required for renewable and sustainable energy conversion.Here,we report a strategy that Pt nanoparticulates are spontaneously immobilized on porous MXene/MAX monolith as HER catalysts by utilizing the redox reaction between Ti3C2Tx MXene and[PtCl4]2 in H2 PtCl6 aqueous solution.By taking advantage of homogeneously distributed Pt nanoparticulates on highly electrically conductive porous Ti3C2Tx/Ti3AlC2 monolith,the as-prepared electrocatalysts show high catalytic performance for hydrogen evolution.Specifically,the binder-free electrocatalysts have Pt loadings as low as 8.9μg/cm^2,with low overpotential of 43 mV at a curre nt density of 10 mA/cm^2 and low Tafel slope that three times lower than porous Ti3C2Tx/Ti3AlC2 without Pt loading.This strategy offers a new approach to constructing ultra-low Pt-loading HER catalysts on the basis of in situ redox reaction between noble metal ions and MXenes.展开更多
Quantum anomalous Hall effect(QAHE)is an innovative topological spintronic phenomenon with dissipationless chiral edge states and attracts rapidly increasing attention.However,it has only been observed in few material...Quantum anomalous Hall effect(QAHE)is an innovative topological spintronic phenomenon with dissipationless chiral edge states and attracts rapidly increasing attention.However,it has only been observed in few materials in experiments.Here,according to the first-principles calculations,we report that the MXene MoYN_(2)CSCl shows a topologically nontrivial band gap of 37.3 me V,possessing QAHE with a Chern number of C=1,which is induced by band inversion between d_(xz)and d_(yz)orbitals.Also,the topological phase transition for the MoYN_(2)CSCl can be realized via strain or by turning the magnetization direction.Remarkably,MoYN_(2)CSCl shows the nodal-line semimetal state dependent on the electron correlation U.Our findings add an experimentally accessible and tunable member to the QAHE family,which stands a chance of enriching the applications in spintronics.展开更多
The biggest challenging issue in photocatalysis is efficient separation of the photoinduced carriers and the aggregation of photoexcited electrons on photocatalyst’s surface.In this paper,we report that double metall...The biggest challenging issue in photocatalysis is efficient separation of the photoinduced carriers and the aggregation of photoexcited electrons on photocatalyst’s surface.In this paper,we report that double metallic co-catalysts Ti3C2 MXene and metallic octahedral(1T)phase tungsten disulfide(WS2)act pathways transferring photoexcited electrons in assisting the photocatalytic H2 evolution.TiO2 nanosheets were in situ grown on highly conductive Ti3C2 MXenes and 1T-WS2 nanoparticles were then uniformly distributed on TiO2@Ti3C2 composite.Thus,a distinctive 1T-WS2@TiO2@Ti3C2 composite with double metallic co-catalysts was achieved,and the content of 1T phase reaches 73%.The photocatalytic H2 evolution performance of 1T-WS2@TiO2@Ti3C2 composite with an optimized 15 wt%WS2 ratio is nearly 50 times higher than that of TiO2 nanosheets because of conductive Ti3C2 MXene and 1T-WS2 resulting in the increase of electron transfer efficiency.Besides,the 1T-WS2 on the surface of TiO2@Ti3C2 composite enhances the Brunauer–Emmett–Teller surface area and boosts the density of active site.展开更多
基金the financial support from the National Natural Science Foundation of China(Grant Nos.11872171,91016014,and 51872062)Fundamental Research Funds for the Central Universities(Grant No.B200202117)。
文摘Transition metal carbide/nitride cores within MXenes make them considerably useful for ultra-high-temperature reinforcement.However,extensive research on Ti_(3)C_(2)T_(x) MXene has revealed its tendency to undergo a phase transition to TiCy at temperatures above 800℃due to high activity of a superficial Ti atomic layer.Herein,spark plasma sintering of Ti_(3)C_(2)T_(x) and TiC is performed to prevent the Ti_(3)C_(2)T_(x) phase transition at temperatures up to 1900℃through the fabrication of composites at a pressure of 50 MPa.Using a focused ion beam scanning electron microscope to separate layered substances in the composites and examining selected area diffraction spots in a transmission electron microscope enabled identification of non-phase-transitioned MXene.First-principles calculations based on density functional theory indicated the formation of strong chemical bonding interfaces between Ti_(3)C_(2)T_(x) and TiC,which imposed a stability constraint on the Ti atomic layer at the Ti_(3)C_(2)T_(x) surface.Mechanical performance tests,such as three-point bending and fracture toughness analysis,demonstrated that the addition of Ti_(3)C_(2)T_(x) can effectively improve the cross-scale strengthening and toughening of the TiC matrix,providing a new path for designing and developing two-dimensional(2D)carbides cross-scale-enhanced three-dimensional(3D)carbides with the same elements relying on a wide variety of MXenes.
基金the National Natural Science Foundation of China(No.U20A20299)Y.C.acknowledges the support from Guangdong Special Support Program(No.2017TX04N371).
文摘With the rapid development of new generations of miniaturized,integrated,and high-power electronic devices,it is particularly important to develop advanced composite materials with efficient thermal management capability and excellent electromagnetic interference(EMI)shielding performance.Herein,an innovative biomass/MXene-derived conductive hybrid scaffold,cellulose nanocrystal(CNC)-konjac glucomannan(KGM)/MXene(CKM),was prepared by freeze-drying and thermal annealing,and then paraffin wax(PW)was encapsulated in CKM using vacuum impregnation method to obtain CNC-KGM/MXene@PW phase change composites(CKMPCCs).The results show that the obtained CKMPCCs possess considerable reusable stabilities,excellent EMI shielding properties,and thermal energy management capacities.Among them,the CKMPCC-6 with 2.3 wt.%MXene exhibits excellent solar-thermal and electro-thermal conversion capabilities.In addition,the EMI shielding effectiveness value is as high as 45.0 dB at 8.2–12.4 GHz and the corresponding melting enthalpy value is 215.7 J/g(relative enthalpy efficiency of 99.9%).In conclusion,the synthesized multifunctional phase change composites provide great potential for integrating outstanding EMI shielding and advanced thermal energy management applications.
基金supported by the National Natural Science Foundation of China (Grant No. 51876112)Project of Shanghai Municipal Science and Technology Commission (Grant No. 21010500600)+1 种基金Shanghai Engineering Research Center of Advanced Thermal Functional MaterialsGaoyuan Discipline of Shanghai-Materials Science and Engineering
文摘Latent heat storage of phase change materials(PCMs)is expected to be a suitable method to enhance the absorption and conversion of solar energy because of their high heat storage density and excellent chemical stability.However,pure organic PCMs are limited by their low thermal conductivity,photothermal conversion,and thermal energy storage efficiency in practical applications.Herein,vertically oriented network composite PCMs are synthesized using reduced graphene oxide/MXene hybrid aerogels(r GO/MXene)as carrier materials and encapsulating stearic acid(SA)as the PCM.Because of the vertically aligned MXene and r GO hybridized backbones,the thermal conductivity of the composite reaches 1.21 W/(m K),which increases 317.24%,compared to SA.The melting enthalpy of composites reaches 168.25 J/g,which almost retains the melting enthalpy of pure SA.The addition of r GO and MXene significantly improves the photothermal conversion capability of composite PCMs(≤90.19%).Irradiating the oriented and non-oriented surfaces of the composite sample,it is found that the temperature rise is faster in the orientation direction than in the non-oriented direction,and the equilibrium temperature of the orientation direction is 4.8°C higher than that of the non-orientation direction.This new material has a high potential for use in solar energy storage applications because of its excellent performance.
基金supported by National Research Foundation of Korea(2019R1A2C1006586).
文摘MXene(M_(n+1)Xn)is an emerging class of layered two-dimensional(2D)materials,which are derived from their bulk-state MAX phase(M_(n+1)AXn,where M:early transition metal,A:group element 13 and 14,and X:carbon and/or nitrogen).MXenes have found wide-ranging applications in energy storage devices,sensors,catalysis,etc.owing to their high electronic conductivity and wide range of optical absorption.However,the absence of semiconducting MXenes has limited their applications related to light emission.Research has shown that quantum dots(QDs)derived from MXene(MQDs)not only retain the properties of the parent MXene but also demonstrate significant improvement on light emission and quantum yield(QY).The optical properties and photoluminescence(PL)emission mechanisms of these light-emitting MQDs have not been comprehensively investigated.Recently,work on light-emitting MQDs has shown good progress,and MQDs exhibiting multi-color PL emission along with high QY have been fabricated.The synthesis methods also play a vital role in determining the light emission properties of these MQDs.This review provides an overview of light-emitting MQDs and their synthesis methods,optical properties,and applications in various optical,sensory,and imaging devices.The future prospects of light-emitting MQDs are also discussed to provide an insight that helps to further advance the progress on MQDs.
基金National Science Foundation,Grant/Award Number:MoMS 1930881China Scholarship Council,Grant/Award Number:201706130028+6 种基金National Natural Science Fund Foundation of China,Grant/Award Number:61775056Natural Science Foundation of Hunan Province,Grant/Award Number:2017JJ1013Research Fund of Science and Technology on Plasma Physics Laboratory,Grant/Award Number:6142A0403050717This work was supported by the National Natural Science Foundation of China(NSFC)(61775056)Natural Science Foundation of Hunan Province(2017JJ1013)Research Fund of Science and Technology on Plasma Physics Laboratory(6142A0403050717)The support provided by China Scholarship Council(CSC)during a visit of Jun Yi to Clemson University is acknowledged.This material is based upon work supported by the National Science Foundation under Grant No.MoMS 1930881.
文摘MXenes,a new class of 2D transition metal carbides,nitrides,and carbonitrides,have attracted much attention due to their outstanding properties.Here,we report the broadband spatial self-phase modulation of Ti2CTx MXene nanosheets dispersed in deionized water in the visible to near-infrared regime,highlighting the broadband nonlinear optical(NLO)response of Ti2CTx MXene.Using ultrafast pulsed laser excitation,the nonlinear refractive index n2 and the thirdorder nonlinear susceptibility χ^(3)monolayer of Ti2CTx MXene were measured to be^10^−13 m^2/W and ~10^−10 esu,respectively.Leveraging the large optical nonlinearity of Ti2CTx MXene,an all-optical modulator in the visible regime was fabricated based on the spatial cross-phase modulation effect.This work suggests that 2D MXenes are ideal broadband NLO materials with excellent prospects in NLO applications.
基金supported by the Youth Innovation Promotion Association,Chinese Academy of Sciences(CAS)(No.2011152)Shenyang National Laboratory for Materials Science,Institute of Metal Research,CASby Special Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund(the second phase)(No.U1501501)。
文摘Designing efficient electrocatalysts with low Pt loadings for hydrogen evolution reaction(HER)is urgently required for renewable and sustainable energy conversion.Here,we report a strategy that Pt nanoparticulates are spontaneously immobilized on porous MXene/MAX monolith as HER catalysts by utilizing the redox reaction between Ti3C2Tx MXene and[PtCl4]2 in H2 PtCl6 aqueous solution.By taking advantage of homogeneously distributed Pt nanoparticulates on highly electrically conductive porous Ti3C2Tx/Ti3AlC2 monolith,the as-prepared electrocatalysts show high catalytic performance for hydrogen evolution.Specifically,the binder-free electrocatalysts have Pt loadings as low as 8.9μg/cm^2,with low overpotential of 43 mV at a curre nt density of 10 mA/cm^2 and low Tafel slope that three times lower than porous Ti3C2Tx/Ti3AlC2 without Pt loading.This strategy offers a new approach to constructing ultra-low Pt-loading HER catalysts on the basis of in situ redox reaction between noble metal ions and MXenes.
基金Project supported by Taishan Scholar Program of Shandong Province,China(Grant No.ts20190939)Independent Cultivation Program of Innovation Team of Jinan City(Grant No.2021GXRC043)+1 种基金Shandong Provincial Natural Science Foundation(Grant No.ZR2020QA052)National Natural Science Foundation of China(Grant Nos.52173283 and 62071200)
文摘Quantum anomalous Hall effect(QAHE)is an innovative topological spintronic phenomenon with dissipationless chiral edge states and attracts rapidly increasing attention.However,it has only been observed in few materials in experiments.Here,according to the first-principles calculations,we report that the MXene MoYN_(2)CSCl shows a topologically nontrivial band gap of 37.3 me V,possessing QAHE with a Chern number of C=1,which is induced by band inversion between d_(xz)and d_(yz)orbitals.Also,the topological phase transition for the MoYN_(2)CSCl can be realized via strain or by turning the magnetization direction.Remarkably,MoYN_(2)CSCl shows the nodal-line semimetal state dependent on the electron correlation U.Our findings add an experimentally accessible and tunable member to the QAHE family,which stands a chance of enriching the applications in spintronics.
基金fundings from the National Natural Science Foundation of China (Nos. 51872173 and 51772167)Taishan Scholarship of Young Scholars (No. tsqn201812068)+2 种基金Natural Science Foundation of Shandong Province (No. ZR2017JL020)Taishan Scholarship of Climbing Plan (No. tspd20161006)Key Research and Development Program of Shandong Province (No. 2018GGX102028)
文摘The biggest challenging issue in photocatalysis is efficient separation of the photoinduced carriers and the aggregation of photoexcited electrons on photocatalyst’s surface.In this paper,we report that double metallic co-catalysts Ti3C2 MXene and metallic octahedral(1T)phase tungsten disulfide(WS2)act pathways transferring photoexcited electrons in assisting the photocatalytic H2 evolution.TiO2 nanosheets were in situ grown on highly conductive Ti3C2 MXenes and 1T-WS2 nanoparticles were then uniformly distributed on TiO2@Ti3C2 composite.Thus,a distinctive 1T-WS2@TiO2@Ti3C2 composite with double metallic co-catalysts was achieved,and the content of 1T phase reaches 73%.The photocatalytic H2 evolution performance of 1T-WS2@TiO2@Ti3C2 composite with an optimized 15 wt%WS2 ratio is nearly 50 times higher than that of TiO2 nanosheets because of conductive Ti3C2 MXene and 1T-WS2 resulting in the increase of electron transfer efficiency.Besides,the 1T-WS2 on the surface of TiO2@Ti3C2 composite enhances the Brunauer–Emmett–Teller surface area and boosts the density of active site.
基金National Natural Science Foundation of China(51731004,52101064,52072003)Anhui Provincial Natural Science Foundation(2008085QE195)+2 种基金National Key Research and Development Program of China(2017YFE0301403)Jiangsu Planned Projects for Postdoctoral Research Funds(2020Z158)Natural Science Foundation of Jiangsu Province(BK20201283)。
