Converting sustainable solar energy into hydrogen energy over semiconductor-based photocatalytic materials provides an alternative to fossil fuel consumption.However,efficient photocatalytic splitting of water to real...Converting sustainable solar energy into hydrogen energy over semiconductor-based photocatalytic materials provides an alternative to fossil fuel consumption.However,efficient photocatalytic splitting of water to realize carbon-free hydrogen production remains a challenge.Heterojunction photocatalysts with well-defined dimensionality and perfectly matched interfaces are promising for achieving highly efficient solar-to-hydrogen conversion.Herein,we report the fabrication of a novel type of protonated graphitic carbon nitride(PCN)/Ti3C2 MXene heterojunctions with strong interfacial interactions.As expected,the two-dimensional(2D)PCN/2D Ti3C2 MXene interface heterojunction achieves a highly improved hydrogen evolution rate(2181μmol∙g‒1)in comparison with bulk g-C3N4(393μmol∙g‒1)and protonated g-C3N4(816μmol∙g‒1).The charge-regulated surfaces of PCN and the accelerated charge transport at the face-to-face 2D/2D Schottky heterojunction interface are the major contributors to the excellent hydrogen evolution performance of the composite photocatalyst.展开更多
MXene has shown distinctive advantages as anode materials of lithium-ion batteries. However, local surface chemistry, which was confirmed that can block ion transfer and limit redox reaction, has a significant effect ...MXene has shown distinctive advantages as anode materials of lithium-ion batteries. However, local surface chemistry, which was confirmed that can block ion transfer and limit redox reaction, has a significant effect on electrochemical performance. Herein, annealing MXene under hydrogen was employed for removing-F and turning-OH to-O terminations. We demonstrate that it improves the kinetics of Li-ion transport between the electrolyte and electrode. As a result, a lower interfacial charge transfer impedance was obtained. The electrochemical measurement exhibited that a nearly 2-fold increase of specific capacity was achieved for the annealed MXene.展开更多
As a powerful non-destructive and label-free detection technology,surface-enhanced Raman scattering(SERS)has been widely used in environmental-pollutant detection,biological-tissue sensing,molecular fingerprint analys...As a powerful non-destructive and label-free detection technology,surface-enhanced Raman scattering(SERS)has been widely used in environmental-pollutant detection,biological-tissue sensing,molecular fingerprint analysis and so on.Different from the traditional SERS substrates represented by noble metals and semiconductors,herein,we report a new highly sensitive SERS substrate material with high stability,biocompatibility,and low cost,namely nucleusfree two-dimensional electron gas(2DEG)Ti3C2 monolayer nanosheets.The highly crystalline monolayer Ti3C2 nanosheets with clean surface are synthesized by an improved chemical exfoliation and microwave heating method.The unique structure of nucleus-free-2DEG in Ti3C2 monolayer provides an ideal transport channel without nuclear scattering,which makes the highly crystalline monolayer Ti3C2 nanosheets achieve a Raman enhanced factor of 3.82×108 and a 10-11 level detection limit for typical environmental pollutants such as azo dyes,trichlorophenol,and bisphenol A.Singlemolecule imaging is also realized on the surface of the Ti3C2 monolayers,which may be the first time that approximate single-molecule imaging has been achieved on a non-noblemetal SERS substrates.Preliminary toxicological experiments show that the cytotoxicity of this material is very low.Considering the facile synthesis,high biocompatibility,low cost and high chemical stability of carbide nanosheets,these Ti3C2 monolayer nanosheets show significant promise for the design and fabrication of flexible SERS substrates for the sensing of trace substances with ultrahigh sensitivity.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
MXenes,a new family of two-dimensional transition metal carbides or nitrides,have attracted tremendous attention for various applications due to their unique properties such as good electrical conductivity,hydrophilic...MXenes,a new family of two-dimensional transition metal carbides or nitrides,have attracted tremendous attention for various applications due to their unique properties such as good electrical conductivity,hydrophilicity,and ion intercalability.In this work,Ti_(3)C_(2) MXene,or MX,is converted to MX-TiO_(2) composites using a simple and rapid microwave hydrothermal treatment in HCl/NaCl mixture solution that induces formation of fine TiO_(2) particles on the MX parent structure and imparts photocatalytic activity to the resulting MX-TiO_(2) composites.The composites were used for enrofloxacin(ENR),a frequently found contaminating antibiotic,removal from water.The relative amount of the MX and TiO_(2) can be controlled by controlling the hydrothermal temperature resulting in composites with tunable adsorption/photocatalytic properties.NaCl addition was found to play important role as composites synthesized without NaCl could not adsorb enrofloxacin well.Adding NaCl into the hydrothermal treatment causes sodium ions to be simultaneously intercalated into the composite structure,improving ENR adsorption greatly from 1 to 6 mg ENR/g composite.It also slows down the MX to TiO2 conversion leading to a smaller and more uniform distribution of TiO_(2) particles on the structure.MX-TiO_(2)/NaCl composites,which have sodium intercalated in their structures,showed both higher ENR adsorption and photocatalytic activity than composites without NaCl despite the latter having higher TiO2 content.Adsorbed ENR on the composites can be efficiently degraded by free radicals generated from the photoexcited TiO2 particles,leading to high photocatalytic degradation efficiency.This demonstrates the synergetic effect between adsorption and photocatalytic degradation of the synthesized compounds.展开更多
Nickel/cobalt-layered double hydroxides(Ni Co-LDH) have been attracted increasing interest in the applications of anode materials for lithium ion battery(LIB), but the low cycle stability and rate performance are stil...Nickel/cobalt-layered double hydroxides(Ni Co-LDH) have been attracted increasing interest in the applications of anode materials for lithium ion battery(LIB), but the low cycle stability and rate performance are still limited its practice applications. To achieve high performance LIB, the surface-confined strategy has been applied to design and fabricate a new anode material of NiCo-LDH nanosheet anchored on the surface of Ti3C2 MXene(Ni Co-LDH/Ti3C2). The ultra-thin, bended and wrinkled α-phase crystal with an interlayer spacing of 8.1 ? can arrange on the conductive substrates Ti3C2 MXene directly, resulting in high electrolyte diffusion ability and low internal resistance. Furthermore, chemical bond interactions between the highly conductive Ti3C2 MXene and Ni Co-LDH nanosheets can greatly increase the ion and electron transport and reduce the volume expansion of NiCo-LDH during Li ion intercalation. As expected,the discharge capacity of 562 m Ah g-1 at 5.0 A g-1 for 800 cycles without degradation can be achieved,rate capability and cycle performance are better than that of NiCo-LDH(~100 mAh g-1). Furthermore, the density function theory(DFT) calculations were performed to demonstrate that Ni Co-LDH/Ti3C2 system can be used as a highly desirable and promising anode material for lithium ion battery.展开更多
Lithium-sulfur(Li-S)batteries with lithium sulfide(Li2S)as cathode have attracted great attention recently,because of high specific capacity(1166 mA h g^-1)of Li2S and potential safety of using Li metal-free anode.Li2...Lithium-sulfur(Li-S)batteries with lithium sulfide(Li2S)as cathode have attracted great attention recently,because of high specific capacity(1166 mA h g^-1)of Li2S and potential safety of using Li metal-free anode.Li2S cathode has lower volume expansion and higher thermal stability than the traditional sulfur cathode.However,the problems of"shuttle effect"and poor electrical conductivity of the cathode material still need to be overcome.In this work,multi-layered Ti3C2/Li2S(ML-Ti3C2/Li2S)composite has been prepared and applied as a cathode in advanced Li-S batteries.The unique multi-layer sheet structure of Ti3 C2 provides space for the storage of Li2S,and its good conductivity greatly enhances the usage ratio of Li2 S and improves the conductivity of the whole Li2S cathode.Compared with commonly used graphene,ML-Ti3C2 can trap polysulfides effectively by chemical adsorption and also activate the reaction of Li2S to polysulfides by forming Ti-S bond.As a result,during the cycling of the batteries with ML-Ti3C2/Li2S cathodes,the activation voltage barrier of the first cycle has decreased to 2.8 V,and the"shuttle effect"has been suppressed effectively.The cycling and rate performances of the ML-Ti3C2/Li2S cathodes have been significantly improved compared to that of graphene/Li2 S cathodes.They maintain a capacity of 450 mAh g^-1 at 0.2 C after 100 cycles,and deliver attractive rate performances of 750,630,540,470 and 360 mAh g^-1 at 0.1 C,0.2 C,0.5 C,1 C,and 2 C,respectively.展开更多
In this study, two-dimensional MXene (Ti3 C2 Tx ) was employed to modify the interface of carbon fiber-reinforced polyetherketoneketone (CF/PEKK) composites, in order to simultaneously improve the electromagnetic inte...In this study, two-dimensional MXene (Ti3 C2 Tx ) was employed to modify the interface of carbon fiber-reinforced polyetherketoneketone (CF/PEKK) composites, in order to simultaneously improve the electromagnetic interference (EMI) shielding performances and mechanical properties. The obtained CF/PEKK composites possessed outstanding EMI and mechanical performances, as anticipated. Specifically, the CF/PEKK composites modified with MXene at 1 mg mL–1 exhibited an excellent EMI shielding effectiveness of 65.2 dB in the X-band, a 103.1% enhancement compared with the unmodified CF/PEKK composites. The attractive EMI shielding performances of CF/PEKK composites originated from enhanced ohmic losses and multiple reflections of electromagnetic waves with the help of the MXene and CF layers. In addition, CF/PEKK composites achieved the best mechanical properties by optimizing the dispersion concentration of MXene to 0.1 mg mL–1 . The flexural strength, flexural modulus, and interlaminar shear strength of CF/PEKK composites reached 1127 MPa, 81 GPa, and 89 MPa, which were 28.5%, 9.5%, and 29.7% higher than that of the unmodified CF/PEKK composites, respectively. Such improvement in mechanical properties could be ascribed to the comprehensive effect of mechanical interlocking, hydrogen bonds, and Van der Waals forces between the introduced MXene and CF, PEKK, respectively.展开更多
Flexible and wearable fiber electrodes with high conductivity and acceptable electrochemical behavior are crucial for extending the application of nextgeneration portable electronics,the development of which,however,i...Flexible and wearable fiber electrodes with high conductivity and acceptable electrochemical behavior are crucial for extending the application of nextgeneration portable electronics,the development of which,however,is very challenging.Two‐dimensional sheets are known to be excellent units for assembling fiber entities,particularly when sheets are oriented in a stacking manner,which helps integrate their intrinsic in‐plane advantages,especially those related with mechanical and electronic performances.In this study,we developed a flexible macroscopic and continuous fiber in an unusual ribbon shape composed solely of Ti3C2 sheets,a typical member of the MXene family.The ribbon morphology was realized through highly ordered stacking of Ti3C2,which imparts fibers with favorable mechanical characteristics.Based on the intrinsic metallic conductivity of Ti3C2 sheets and the oriented stacking structure,the developed macroscopic ribbon exhibited excellent conductivity for both electrons(up to 2458 S/cm)and ions.A fiber‐shaped asymmetric supercapacitor using the developed macroscopic ribbon as a cathode coupled with reduced graphene oxide fibers as an anode delivered a competitive maximum volumetric energy density of 58.4mWh/cm3(20.0Wh/kg)while maintaining a power level of 1679.0mW/cm3(581.0 W/kg)and excellent cycling stability(92.4%retention after 10000 cycles at 10 A/g).This study highlights the excellent potential of MXene as a platform for macroscopic assembly and definitely broadens the applications of MXene materials in wearable electronics.展开更多
Transition metal carbide or nitride(MXene)is regarded as next-generation two-dimensional(2D)materials for various applications,such as photocatalysis,electrocatalysis,supercapacitor,lithium-ion battery and biomedicine...Transition metal carbide or nitride(MXene)is regarded as next-generation two-dimensional(2D)materials for various applications,such as photocatalysis,electrocatalysis,supercapacitor,lithium-ion battery and biomedicine,because of its unique physicochemical properties.In photocatalysis,MXene could allow fast photogenerated charge carrier separation and provide abundant surface functional groups for light harvesting materials,rendering feasible the high photoconversion efficiency.Therefore,enormous theoretical and experimental studies have been recently made and shown the potential of MXene in various photocatalytic applications.Here,we provide a brief overview of the MXene-based materials,along with their functions in photocatalytic applications.Then,we summarize the recent advances and progresses of MXene-based photocatalysts,ranging from solar fuel production to pollutant degradation.Finally,we present concluding remarks and the outlooks for achieving highly efficient MXene-based photocatalysts.展开更多
Silicon offers a high theoretical specific capacity for anodic lithium storage.However,its applications are hindered by the electrode instability caused by the sharp volume change,and the limited rate performance resu...Silicon offers a high theoretical specific capacity for anodic lithium storage.However,its applications are hindered by the electrode instability caused by the sharp volume change,and the limited rate performance resulted from the insulating property.Herein,we introduce a facile and fast method of preparing honeycomb‐like silicon‐based anodes(MXene‐Si@C)with porous structure using MXene and carbon‐coated silicon.The dual protection from both the surface coating and as‐formed interlayered vacant spaces ameliorate the volume expansion of the silicon and thus reinforce the mechanical stability of the electrode.In addition,the highly conducting MXene and the surface carbon coating form a hierarchical and consecutive electron‐conducting network with evidently reduced resistance.With this proposed composite,a high average Coulombic efficiency of 99.73%and high capacity retention of 82.4%after 300 cycles at 1 A/g can be achieved even with an areal loading around 1.5 mg/cm^(2).Coupled with an NCM523 cathode,the proof‐of‐concept full cell delivers a high capacity of 164.2mAh/g with an extremely high energy density of 574Wh/kg(based on the mass of the electrode materials)at 0.2 C and an excellent cyclability at 0.5 C of 100 cycles with decent capacity retention(80.28%).展开更多
Although Si-based nanomaterials provide incomparable lithium ion storage ability in theory, it suffers from low initial Coulombic efficiency, electrical disconnection, and fracture due to huge volume changes after ext...Although Si-based nanomaterials provide incomparable lithium ion storage ability in theory, it suffers from low initial Coulombic efficiency, electrical disconnection, and fracture due to huge volume changes after extended cycles. As a result, it leads to a severe capacity fading and an increase in internal impedance. Herein, Ti-elemental MXene was employed as a matrix for the intermediate product of Si electrodes. The boundary between the inner core of pristine Si and its outer shell of amorphous Li x Si alloy was reconstructed. Smaller amorphous aggregates were observed in the MXene&Si hybrid electrode after 500 cycles by using transmission electron microscopy. Consequently, an enhanced specific capacity was achieved as MXene as a matrix enables loading amorphous Si.展开更多
文摘Converting sustainable solar energy into hydrogen energy over semiconductor-based photocatalytic materials provides an alternative to fossil fuel consumption.However,efficient photocatalytic splitting of water to realize carbon-free hydrogen production remains a challenge.Heterojunction photocatalysts with well-defined dimensionality and perfectly matched interfaces are promising for achieving highly efficient solar-to-hydrogen conversion.Herein,we report the fabrication of a novel type of protonated graphitic carbon nitride(PCN)/Ti3C2 MXene heterojunctions with strong interfacial interactions.As expected,the two-dimensional(2D)PCN/2D Ti3C2 MXene interface heterojunction achieves a highly improved hydrogen evolution rate(2181μmol∙g‒1)in comparison with bulk g-C3N4(393μmol∙g‒1)and protonated g-C3N4(816μmol∙g‒1).The charge-regulated surfaces of PCN and the accelerated charge transport at the face-to-face 2D/2D Schottky heterojunction interface are the major contributors to the excellent hydrogen evolution performance of the composite photocatalyst.
基金financial support provided by the National Key R&D Program of China (2016YFA0200400)the Jilin Province/Jilin University co-Construction Project-Funds for New Materials (SXGJSF2017-3, Branch-2/440050316A36)+4 种基金the National Natural Science Foundation of China (Grant nos. 91545119, 21761132025, 21773269 and 51372095)the Youth Innovation Promotion Association CAS (Grant no. 2015152)Strategic Priority Research Program of the Chinese Academy of Sciences Chinese Academy of Sciences (Grant nos. XDA09030103 and XDA09040203)the Program for JLU Science and Technology Innovative Research Team (JLUSTIRT)"Double-First Class" Discipline for Materials Science & Engineering
文摘MXene has shown distinctive advantages as anode materials of lithium-ion batteries. However, local surface chemistry, which was confirmed that can block ion transfer and limit redox reaction, has a significant effect on electrochemical performance. Herein, annealing MXene under hydrogen was employed for removing-F and turning-OH to-O terminations. We demonstrate that it improves the kinetics of Li-ion transport between the electrolyte and electrode. As a result, a lower interfacial charge transfer impedance was obtained. The electrochemical measurement exhibited that a nearly 2-fold increase of specific capacity was achieved for the annealed MXene.
基金support from the Science Foundation of Chinese Academy of Inspection and Quarantine(2019JK004)the National Key Research and Development Program of China(2017YFF0210003)the high performance computing center of Qufu Normal University。
文摘As a powerful non-destructive and label-free detection technology,surface-enhanced Raman scattering(SERS)has been widely used in environmental-pollutant detection,biological-tissue sensing,molecular fingerprint analysis and so on.Different from the traditional SERS substrates represented by noble metals and semiconductors,herein,we report a new highly sensitive SERS substrate material with high stability,biocompatibility,and low cost,namely nucleusfree two-dimensional electron gas(2DEG)Ti3C2 monolayer nanosheets.The highly crystalline monolayer Ti3C2 nanosheets with clean surface are synthesized by an improved chemical exfoliation and microwave heating method.The unique structure of nucleus-free-2DEG in Ti3C2 monolayer provides an ideal transport channel without nuclear scattering,which makes the highly crystalline monolayer Ti3C2 nanosheets achieve a Raman enhanced factor of 3.82×108 and a 10-11 level detection limit for typical environmental pollutants such as azo dyes,trichlorophenol,and bisphenol A.Singlemolecule imaging is also realized on the surface of the Ti3C2 monolayers,which may be the first time that approximate single-molecule imaging has been achieved on a non-noblemetal SERS substrates.Preliminary toxicological experiments show that the cytotoxicity of this material is very low.Considering the facile synthesis,high biocompatibility,low cost and high chemical stability of carbide nanosheets,these Ti3C2 monolayer nanosheets show significant promise for the design and fabrication of flexible SERS substrates for the sensing of trace substances with ultrahigh sensitivity.
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 Nanotechnology Center (NANOTEC) (No.P1751698) for financial supportThailand Advanced Institute of Science and Technology and Tokyo Institute of Technology (TAIST-Tokyo Tech) for collaborative program and scholarship supports+1 种基金supported by Thammasat University Research Fund Contract No.TUFT 055/2563Support from Center of Excellence in Functional Advanced Materials Engineering (CoE FAME),SIIT
文摘MXenes,a new family of two-dimensional transition metal carbides or nitrides,have attracted tremendous attention for various applications due to their unique properties such as good electrical conductivity,hydrophilicity,and ion intercalability.In this work,Ti_(3)C_(2) MXene,or MX,is converted to MX-TiO_(2) composites using a simple and rapid microwave hydrothermal treatment in HCl/NaCl mixture solution that induces formation of fine TiO_(2) particles on the MX parent structure and imparts photocatalytic activity to the resulting MX-TiO_(2) composites.The composites were used for enrofloxacin(ENR),a frequently found contaminating antibiotic,removal from water.The relative amount of the MX and TiO_(2) can be controlled by controlling the hydrothermal temperature resulting in composites with tunable adsorption/photocatalytic properties.NaCl addition was found to play important role as composites synthesized without NaCl could not adsorb enrofloxacin well.Adding NaCl into the hydrothermal treatment causes sodium ions to be simultaneously intercalated into the composite structure,improving ENR adsorption greatly from 1 to 6 mg ENR/g composite.It also slows down the MX to TiO2 conversion leading to a smaller and more uniform distribution of TiO_(2) particles on the structure.MX-TiO_(2)/NaCl composites,which have sodium intercalated in their structures,showed both higher ENR adsorption and photocatalytic activity than composites without NaCl despite the latter having higher TiO2 content.Adsorbed ENR on the composites can be efficiently degraded by free radicals generated from the photoexcited TiO2 particles,leading to high photocatalytic degradation efficiency.This demonstrates the synergetic effect between adsorption and photocatalytic degradation of the synthesized compounds.
基金Rachadapisek Sompoch project,Chulalongkorn University(CU_GR_62_14_62_02)the Energy Conservation and Promotion Fund Office,Ministry of Energy+2 种基金the NSFC(grant 51421091)National Science Foundation for Distinguished Young Scholars for Hebei Province of China(grant E2016203376)Asahi Glass Foundation。
文摘Nickel/cobalt-layered double hydroxides(Ni Co-LDH) have been attracted increasing interest in the applications of anode materials for lithium ion battery(LIB), but the low cycle stability and rate performance are still limited its practice applications. To achieve high performance LIB, the surface-confined strategy has been applied to design and fabricate a new anode material of NiCo-LDH nanosheet anchored on the surface of Ti3C2 MXene(Ni Co-LDH/Ti3C2). The ultra-thin, bended and wrinkled α-phase crystal with an interlayer spacing of 8.1 ? can arrange on the conductive substrates Ti3C2 MXene directly, resulting in high electrolyte diffusion ability and low internal resistance. Furthermore, chemical bond interactions between the highly conductive Ti3C2 MXene and Ni Co-LDH nanosheets can greatly increase the ion and electron transport and reduce the volume expansion of NiCo-LDH during Li ion intercalation. As expected,the discharge capacity of 562 m Ah g-1 at 5.0 A g-1 for 800 cycles without degradation can be achieved,rate capability and cycle performance are better than that of NiCo-LDH(~100 mAh g-1). Furthermore, the density function theory(DFT) calculations were performed to demonstrate that Ni Co-LDH/Ti3C2 system can be used as a highly desirable and promising anode material for lithium ion battery.
基金financially supported by the National Natural Science Foundation of China(21606065,51372060,and 21676067)Anhui Provincial Natural Science Foundation(1708085QE98)+1 种基金the Fundamental Research Funds for the Central Universities(JZ2017HGTB0198,JZ2018HGBZ0138)the Opening Project of CAS Key Laboratory of Materials for Energy Conversion(KF2018003)
文摘Lithium-sulfur(Li-S)batteries with lithium sulfide(Li2S)as cathode have attracted great attention recently,because of high specific capacity(1166 mA h g^-1)of Li2S and potential safety of using Li metal-free anode.Li2S cathode has lower volume expansion and higher thermal stability than the traditional sulfur cathode.However,the problems of"shuttle effect"and poor electrical conductivity of the cathode material still need to be overcome.In this work,multi-layered Ti3C2/Li2S(ML-Ti3C2/Li2S)composite has been prepared and applied as a cathode in advanced Li-S batteries.The unique multi-layer sheet structure of Ti3 C2 provides space for the storage of Li2S,and its good conductivity greatly enhances the usage ratio of Li2 S and improves the conductivity of the whole Li2S cathode.Compared with commonly used graphene,ML-Ti3C2 can trap polysulfides effectively by chemical adsorption and also activate the reaction of Li2S to polysulfides by forming Ti-S bond.As a result,during the cycling of the batteries with ML-Ti3C2/Li2S cathodes,the activation voltage barrier of the first cycle has decreased to 2.8 V,and the"shuttle effect"has been suppressed effectively.The cycling and rate performances of the ML-Ti3C2/Li2S cathodes have been significantly improved compared to that of graphene/Li2 S cathodes.They maintain a capacity of 450 mAh g^-1 at 0.2 C after 100 cycles,and deliver attractive rate performances of 750,630,540,470 and 360 mAh g^-1 at 0.1 C,0.2 C,0.5 C,1 C,and 2 C,respectively.
基金supported by the Shanghai Science and Tech-nology Committee(No.22511102400)Prof.Zhang would like to appreciate the financial support from the Fundamental Research Funds for the Central Universities(No.2232020G-12)+1 种基金the Fund of National Engineering Research Center for Commercial Aircraft Manufacturing(No.COMAC-SFGS-2022-2376)the Textile Vi-sion Basic Research Program(No.J202105).
文摘In this study, two-dimensional MXene (Ti3 C2 Tx ) was employed to modify the interface of carbon fiber-reinforced polyetherketoneketone (CF/PEKK) composites, in order to simultaneously improve the electromagnetic interference (EMI) shielding performances and mechanical properties. The obtained CF/PEKK composites possessed outstanding EMI and mechanical performances, as anticipated. Specifically, the CF/PEKK composites modified with MXene at 1 mg mL–1 exhibited an excellent EMI shielding effectiveness of 65.2 dB in the X-band, a 103.1% enhancement compared with the unmodified CF/PEKK composites. The attractive EMI shielding performances of CF/PEKK composites originated from enhanced ohmic losses and multiple reflections of electromagnetic waves with the help of the MXene and CF layers. In addition, CF/PEKK composites achieved the best mechanical properties by optimizing the dispersion concentration of MXene to 0.1 mg mL–1 . The flexural strength, flexural modulus, and interlaminar shear strength of CF/PEKK composites reached 1127 MPa, 81 GPa, and 89 MPa, which were 28.5%, 9.5%, and 29.7% higher than that of the unmodified CF/PEKK composites, respectively. Such improvement in mechanical properties could be ascribed to the comprehensive effect of mechanical interlocking, hydrogen bonds, and Van der Waals forces between the introduced MXene and CF, PEKK, respectively.
基金This study was supported by the National Natural Science Foundation of China(Grant no.51772201)Jiangsu Specially‐Appointed Professor Programand a project funded by the Priority Academic Program Developmentof Jiangsu Higher Education Institutions.
文摘Flexible and wearable fiber electrodes with high conductivity and acceptable electrochemical behavior are crucial for extending the application of nextgeneration portable electronics,the development of which,however,is very challenging.Two‐dimensional sheets are known to be excellent units for assembling fiber entities,particularly when sheets are oriented in a stacking manner,which helps integrate their intrinsic in‐plane advantages,especially those related with mechanical and electronic performances.In this study,we developed a flexible macroscopic and continuous fiber in an unusual ribbon shape composed solely of Ti3C2 sheets,a typical member of the MXene family.The ribbon morphology was realized through highly ordered stacking of Ti3C2,which imparts fibers with favorable mechanical characteristics.Based on the intrinsic metallic conductivity of Ti3C2 sheets and the oriented stacking structure,the developed macroscopic ribbon exhibited excellent conductivity for both electrons(up to 2458 S/cm)and ions.A fiber‐shaped asymmetric supercapacitor using the developed macroscopic ribbon as a cathode coupled with reduced graphene oxide fibers as an anode delivered a competitive maximum volumetric energy density of 58.4mWh/cm3(20.0Wh/kg)while maintaining a power level of 1679.0mW/cm3(581.0 W/kg)and excellent cycling stability(92.4%retention after 10000 cycles at 10 A/g).This study highlights the excellent potential of MXene as a platform for macroscopic assembly and definitely broadens the applications of MXene materials in wearable electronics.
基金finically supported by the National Natural Science Foundation of China(Nos.51932007,U1705251,U1905215,21950410514,51961135303 and 21871217)the National Key Research and Development Program of China(No.2018YFB1502001)+2 种基金the China Postdoctoral Science Foundation(Nos.2019TQ0237 and 2019M652190)the Chinese Academy of Sciences President’s International Fellowship Initiative(No.2019PC0114)the Fundamental Research Funds for the Central Universities(No.WUT:2019IVA109)。
文摘Transition metal carbide or nitride(MXene)is regarded as next-generation two-dimensional(2D)materials for various applications,such as photocatalysis,electrocatalysis,supercapacitor,lithium-ion battery and biomedicine,because of its unique physicochemical properties.In photocatalysis,MXene could allow fast photogenerated charge carrier separation and provide abundant surface functional groups for light harvesting materials,rendering feasible the high photoconversion efficiency.Therefore,enormous theoretical and experimental studies have been recently made and shown the potential of MXene in various photocatalytic applications.Here,we provide a brief overview of the MXene-based materials,along with their functions in photocatalytic applications.Then,we summarize the recent advances and progresses of MXene-based photocatalysts,ranging from solar fuel production to pollutant degradation.Finally,we present concluding remarks and the outlooks for achieving highly efficient MXene-based photocatalysts.
基金supported by a grant from the Research Grants Council of the Hong Kong Special Administrative Region,China(Project No.T23‐601/17‐R).
文摘Silicon offers a high theoretical specific capacity for anodic lithium storage.However,its applications are hindered by the electrode instability caused by the sharp volume change,and the limited rate performance resulted from the insulating property.Herein,we introduce a facile and fast method of preparing honeycomb‐like silicon‐based anodes(MXene‐Si@C)with porous structure using MXene and carbon‐coated silicon.The dual protection from both the surface coating and as‐formed interlayered vacant spaces ameliorate the volume expansion of the silicon and thus reinforce the mechanical stability of the electrode.In addition,the highly conducting MXene and the surface carbon coating form a hierarchical and consecutive electron‐conducting network with evidently reduced resistance.With this proposed composite,a high average Coulombic efficiency of 99.73%and high capacity retention of 82.4%after 300 cycles at 1 A/g can be achieved even with an areal loading around 1.5 mg/cm^(2).Coupled with an NCM523 cathode,the proof‐of‐concept full cell delivers a high capacity of 164.2mAh/g with an extremely high energy density of 574Wh/kg(based on the mass of the electrode materials)at 0.2 C and an excellent cyclability at 0.5 C of 100 cycles with decent capacity retention(80.28%).
基金financial support provided by the Joint Foundation of Liaoning Province National Science FoundationShenyang National Laboratory for Materials Science (Grant No. 20180510047)+6 种基金the National Natural Science Foundation of China (Grant Nos. 91545119 , 21761132025 , 21773269 and 51872115)the Youth Innovation Promotion Association CAS (Grant No. 2015152)the Program for JLU Science and Technology Innovative Research Team (JLUSTIRT, 2017TD-09)“Double-First Class” Discipline for Materials Science & EngineeringNatural Science Foundation of Anhui Province (1608085ME93)the Fundamental Research Funds for the Central Universities (JZ2018YYPY0305)the 111 Project “New Materials and Technology for Clean Energy” (B18018)
文摘Although Si-based nanomaterials provide incomparable lithium ion storage ability in theory, it suffers from low initial Coulombic efficiency, electrical disconnection, and fracture due to huge volume changes after extended cycles. As a result, it leads to a severe capacity fading and an increase in internal impedance. Herein, Ti-elemental MXene was employed as a matrix for the intermediate product of Si electrodes. The boundary between the inner core of pristine Si and its outer shell of amorphous Li x Si alloy was reconstructed. Smaller amorphous aggregates were observed in the MXene&Si hybrid electrode after 500 cycles by using transmission electron microscopy. Consequently, an enhanced specific capacity was achieved as MXene as a matrix enables loading amorphous Si.
