The outbreak of coronavirus disease 2019 has seriously threatened human health.Rapidly and sensitively detecting SARSCoV-2 viruses can help control the spread of viruses.However,it is an arduous challenge to apply sem...The outbreak of coronavirus disease 2019 has seriously threatened human health.Rapidly and sensitively detecting SARSCoV-2 viruses can help control the spread of viruses.However,it is an arduous challenge to apply semiconductor-based substrates for virus SERS detection due to their poor sensitivity.Therefore,it is worthwhile to search novel semiconductor-based substrates with excellent SERS sensitivity.Herein we report,for the first time,Nb2C and Ta2C MXenes exhibit a remarkable SERS enhancement,which is synergistically enabled by the charge transfer resonance enhancement and electromagnetic enhancement.Their SERS sensitivity is optimized to 3.0×10^6 and 1.4×10^6 under the optimal resonance excitation wavelength of 532 nm.Additionally,remarkable SERS sensitivity endows Ta2C MXenes with capability to sensitively detect and accurately identify the SARS-CoV-2 spike protein.Moreover,its detection limit is as low as 5×10^−9 M,which is beneficial to achieve real-time monitoring and early warning of novel coronavirus.This research not only provides helpful theoretical guidance for exploring other novel SERS-active semiconductor-based materials but also provides a potential candidate for the practical applications of SERS technology.展开更多
Early surgical resection and chemotherapy of bone cancer are commonly used in the treatment of bone tumor,but it is still highly challenging to prevent recurrence and fill the bone defect caused by the resection site....Early surgical resection and chemotherapy of bone cancer are commonly used in the treatment of bone tumor,but it is still highly challenging to prevent recurrence and fill the bone defect caused by the resection site.In this work,we report a rational integration of photonic-responsive two-dimensional(2D)ultrathin niobium carbide(Nb2C)MXene nanosheets(NSs)into the 3D-printed bone-mimetic scaffolds(NBGS)for osteosarcoma treatment.The integrated 2D Nb2C-MXene NSs feature specific photonic response in the second near-infrared(NIR-II)biowindow with high tissue-penetrating depth,making it highly efficient in killing bone cancer cells.Importantly,Nb-based species released by the biodegradation of Nb2C MXene can obviously promote the neogenesis and migration of blood vessels in the defect site,which can transport more oxygen,vitamins and energy around the bone defect for the reparative process,and gather more immune cells around the defect site to accelerate the degradation of NBGS.The degradation of NBGS provides sufficient space for the bone remodeling.Besides,calcium and phosphate released during the degradation of the scaffold can promote the mineralization of new bone tissue.The intrinsic multifunctionality of killing bone tumor cell and promoting angiogenesis and bone regeneration makes the engineered Nb2C MXeneintegrated composite scaffolds a distinctive implanting biomaterial on the efficient treatment of bone tumor.展开更多
Lithium-ion capacitors(LICs)are becoming important electrochemical energy storage systems due to their great potential to bridge the gap between supercapacitors and lithium-ion batteries.However,capacity lopsidedness ...Lithium-ion capacitors(LICs)are becoming important electrochemical energy storage systems due to their great potential to bridge the gap between supercapacitors and lithium-ion batteries.However,capacity lopsidedness and low output voltage greatly hinder the realization of high-energy-density LICs.Herein,a strategy of balancing capacity towards fastest dynamics is proposed to enable high-voltage LICs.Through electrochemical prelithiation of Nb_(2)C to be 1.1 V with 165 mAh g^(-1),Nb_(2)C//LiFePO_(4) LICs show a broadened potential window from 3.0 to 4.2 V and an according high energy density of 420 Wh kg^(-1).Moreover,the underlying mechanism between prelithiation and high voltage is disclosed by electrochemical dynamic analysis.Prelithiation declines the Nb_(2)C anode potential that facilitates electron transmission in the interlayer of two-dimensional Nb_(2)C MXene.This effect induces small drive force for Li^(+)ions deposition and hence weakens the repulsive force from adsorbed ions on the electrode surface.Benefiting from even more Li^(+)ions deposition,a higher voltage is eventually delivered.In addition,prelithiation significantly increases Coulomb efficiency of the 1st cycle from 74%to 90%,which is crucial to commercial application of LICs.展开更多
Niobium carbide MXene quantum dots(Nb2 C MQDs)derived from 2 D Nb2 CTx(MXene)are the rising-star material recently.Herein,a sulfur and nitrogen co-doped Nb2 C MQDs(S,N-MQDs)were synthesized through a hydrothermal meth...Niobium carbide MXene quantum dots(Nb2 C MQDs)derived from 2 D Nb2 CTx(MXene)are the rising-star material recently.Herein,a sulfur and nitrogen co-doped Nb2 C MQDs(S,N-MQDs)were synthesized through a hydrothermal method.The obtained Nb2 C MQDs have excellent green fluorescence with a quantum yield(QY)of 17.25%.In addition,they exhibited excitatio n-dependent photoluminescence,antiphotobleaching and dispersion stability.They emit light at 520 nm when excited at 390 nm.The Nb2 C MQDs could be successfully applied to copper ion detection with detection limit of 2μmol/L and Caco-2 cells imaging.展开更多
The Li-Mg-B-H composite(2LiBH_(4)+MgH_(2))has a high capacity of 11.4 wt%as a hydrogen storage material.However,the slow kinetics and poor cycling stability severely restrict its practical applications.In this work,a ...The Li-Mg-B-H composite(2LiBH_(4)+MgH_(2))has a high capacity of 11.4 wt%as a hydrogen storage material.However,the slow kinetics and poor cycling stability severely restrict its practical applications.In this work,a layered Nb_(2)C MXene was first synthesized and then introduced to tailor the kinetics and cycling stability of the Li-Mg-B-H composite.The milled 2LiH+MgB_(2)composites were initially hydrogenated to obtain the 2LiBH_(4)+MgH_(2)composites.The 2LiBH_(4)+MgH_(2)+5wt%Nb_(2)C can release 9.0 wt%H_(2)in 30 min at 400℃,while it is only 2.7 wt%for the undoped 2LiBH_(4)+MgH_(2).The dehydrogenation activation energies of MgH_(2)and LiBH_(4)are 123 and 154 kJ·mol^(-1)respectively for the 5 wt%Nb_(2)C-doped composite,lower than the undoped composite(164 and 165 kJ·mol^(-1)).The 2LiBH_(4)+MgH_(2)+5 wt%Nb_(2)C possesses excellent cycling stability,with the reversible capacity only slightly reduced from 9.4 wt%for the 1st cycle to 9.3 wt%for the 20th cycle.Nb_(2)C keeps stable in the composite and acts as an efficient catalyst for the Li-Mg-B-H composite.It is believed that both the layered structure and the active Nb element contribu te to the enhanced hydrogen storage performances of the Li-Mg-B-H composite.This work confirms that the Nb_(2)C MXene with layered stru cture has a significant enhancing impact on the Li-Mg-B-H hydrogen storage materials,which is different from the bulk NbC.展开更多
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
Novel two-dimensional(2D)Nb_(2)C nanosheets were successfully prepared through a simple lultrasonic and magnetic stirring treatment from the original accordion-like powder.To further study their water-lubrication prop...Novel two-dimensional(2D)Nb_(2)C nanosheets were successfully prepared through a simple lultrasonic and magnetic stirring treatment from the original accordion-like powder.To further study their water-lubrication properties and deal with common oxidation problems,Nb_(2)C nanosheets with different oxidation degrees were prepared and achieved long-term stability in deionized water.Scanning electron microscope(SEM),transmission electron microscope(TEM),scanning probe microscope(SPM),X-ray powder diffraction(XRD),Raman,and X-ray photoelectron spectrometer(XPS)experiments were utilized to characterize the structure,morphology,and dispersion of Nb_(2)C nanosheets with different degrees of oxidation.The tribological behaviors of Nb_(2)C with different degrees of oxidation as additives for water lubrication were characterized using a UMT-3 friction testing machine.The wear scars formed on the 316 steel surface were measured using three-dimensional(3D)laser scanning confocal microscopy.The tribological results showed that a moderately oxidized Nb_(2)C nanosheet,which owned the composition of Nb_(2)C/Nb_(2)O5/C,displayed excellent tribological performance,with the friction coefficient(COF)decreasing by 90.3%and a decrease in the wear rate by 73.1%compared with pure water.Combining the TEM and Raman spectra,it was shown that Nb_(2)O5 nanoparticles filled in the worn zone,and the layered Nb_(2)C and C were adsorbed into the surface of the friction pair to form a protective lubricating film.This combined action resulted in an excellent lubricating performance.展开更多
Extensive research has been devoted to lithium-sulfur(Li-S)batteries due to their overwhelming promises and advantages such as high theoretical capacity(1675 m Ah g^(-1)),extremely cost effectiveness and abundance and...Extensive research has been devoted to lithium-sulfur(Li-S)batteries due to their overwhelming promises and advantages such as high theoretical capacity(1675 m Ah g^(-1)),extremely cost effectiveness and abundance and availability of sulfur.Nevertheless,a sluggish electrochemical kinetics of the battery limited by a slow conversion of lithium polysulfide(LiPSs)intermediates and Li PSs shuttle effect severely hinder its development towards industrial application.Herein,we designed the oxidized Nb2_(C)MXene with amorphous carbon(Nb_(2)O_(5)/C)composites as sulfur host using CO_(2)treatment to address the above issues.The Nb_(2)O_(5)/C composites with high conductivity are directly employed as sulfur hosts for Li-S battery capable to remarkably mitigate the shuttle phenomenon due to a combined effect of their Li PSs trapping ability and catalytic activity towards their accelerated conversion.Meanwhile,the unique layered structure of the composite facilitates ion transfer and accommodates the volume changes of the cathode during cycling.With this rational design,the resultant Li-S batteries exhibit superior electrochemical performance with a high initial specific capacity of 745 m Ah g^(-1)at 1.0 C and a reversible capacity of 620 m Ah g^(-1)at a high rate cycling at 3.0 C.展开更多
MXenes are a new type of two-dimensional carbides with rich physical and chemical properties. The physics of MXenes, and thus the applications, are dominated by surface functional groups. Herein, the effects of differ...MXenes are a new type of two-dimensional carbides with rich physical and chemical properties. The physics of MXenes, and thus the applications, are dominated by surface functional groups. Herein, the effects of different terminations(O,S, Se, Te) on the geometric and electronic properties of Nb_(2)C MXenes were studied via density functional theory(DFT)calculations. Three adsorption sites were examined to determine the most stable configurations. The results showed that both the types and the positions of surface functional groups influence the geometric stability and physical characters of Nb_(2)C. The S and Se terminations make the Nb_(2)C MXenes to be semiconductor, while Nb_(2)C MXenes with other terminations(O, Te) are conductor. The electron location function, density of states, Bader charge distribution, and the projected crystal orbital Hamilton population were conducted to explain the origin of adsorption stability and electronic nature difference. Our results provide a fundamental understanding about the effects of surface terminations on the intrinsic stability and electronic properties of Nb_(2)C MXenes.展开更多
基金The authors gratefully acknowledge the finical support of the National Key Research and Development Project(No.2017YFB0310600)this work is also supported by Shanghai International Science and Technology Cooperation Fund(Nos.17520711700 and 18520744200).
文摘The outbreak of coronavirus disease 2019 has seriously threatened human health.Rapidly and sensitively detecting SARSCoV-2 viruses can help control the spread of viruses.However,it is an arduous challenge to apply semiconductor-based substrates for virus SERS detection due to their poor sensitivity.Therefore,it is worthwhile to search novel semiconductor-based substrates with excellent SERS sensitivity.Herein we report,for the first time,Nb2C and Ta2C MXenes exhibit a remarkable SERS enhancement,which is synergistically enabled by the charge transfer resonance enhancement and electromagnetic enhancement.Their SERS sensitivity is optimized to 3.0×10^6 and 1.4×10^6 under the optimal resonance excitation wavelength of 532 nm.Additionally,remarkable SERS sensitivity endows Ta2C MXenes with capability to sensitively detect and accurately identify the SARS-CoV-2 spike protein.Moreover,its detection limit is as low as 5×10^−9 M,which is beneficial to achieve real-time monitoring and early warning of novel coronavirus.This research not only provides helpful theoretical guidance for exploring other novel SERS-active semiconductor-based materials but also provides a potential candidate for the practical applications of SERS technology.
基金the financial support from the National Key R&D Program of China(Grant No.2016YFA0203700)the National Natural Science Foundation of China(Grant Nos.51872185,51722211,51672303,81672131,81672143,82072417 and 81802247)+2 种基金the Program of Shanghai Academic Research Leader(Grant No.18XD1404300)the National Key Research and Development Project of China(Grant No.2018YFC1106303)the Science and Technology Commission of Shanghai Municipality(Grant No.17060502400).
文摘Early surgical resection and chemotherapy of bone cancer are commonly used in the treatment of bone tumor,but it is still highly challenging to prevent recurrence and fill the bone defect caused by the resection site.In this work,we report a rational integration of photonic-responsive two-dimensional(2D)ultrathin niobium carbide(Nb2C)MXene nanosheets(NSs)into the 3D-printed bone-mimetic scaffolds(NBGS)for osteosarcoma treatment.The integrated 2D Nb2C-MXene NSs feature specific photonic response in the second near-infrared(NIR-II)biowindow with high tissue-penetrating depth,making it highly efficient in killing bone cancer cells.Importantly,Nb-based species released by the biodegradation of Nb2C MXene can obviously promote the neogenesis and migration of blood vessels in the defect site,which can transport more oxygen,vitamins and energy around the bone defect for the reparative process,and gather more immune cells around the defect site to accelerate the degradation of NBGS.The degradation of NBGS provides sufficient space for the bone remodeling.Besides,calcium and phosphate released during the degradation of the scaffold can promote the mineralization of new bone tissue.The intrinsic multifunctionality of killing bone tumor cell and promoting angiogenesis and bone regeneration makes the engineered Nb2C MXeneintegrated composite scaffolds a distinctive implanting biomaterial on the efficient treatment of bone tumor.
基金financial supported from the National Natural Science Foundation of China (Nos. 51977185 and 51972277)the financial supported from Southwest Jiaotong University Science and Technology Rising Star Program (No. 2682021CG021)
文摘Lithium-ion capacitors(LICs)are becoming important electrochemical energy storage systems due to their great potential to bridge the gap between supercapacitors and lithium-ion batteries.However,capacity lopsidedness and low output voltage greatly hinder the realization of high-energy-density LICs.Herein,a strategy of balancing capacity towards fastest dynamics is proposed to enable high-voltage LICs.Through electrochemical prelithiation of Nb_(2)C to be 1.1 V with 165 mAh g^(-1),Nb_(2)C//LiFePO_(4) LICs show a broadened potential window from 3.0 to 4.2 V and an according high energy density of 420 Wh kg^(-1).Moreover,the underlying mechanism between prelithiation and high voltage is disclosed by electrochemical dynamic analysis.Prelithiation declines the Nb_(2)C anode potential that facilitates electron transmission in the interlayer of two-dimensional Nb_(2)C MXene.This effect induces small drive force for Li^(+)ions deposition and hence weakens the repulsive force from adsorbed ions on the electrode surface.Benefiting from even more Li^(+)ions deposition,a higher voltage is eventually delivered.In addition,prelithiation significantly increases Coulomb efficiency of the 1st cycle from 74%to 90%,which is crucial to commercial application of LICs.
基金the National Nature Science Foundation of China(No.31340014)the Youth Development Project of Medical Technologyin Army(No.13QNP166)+1 种基金the Key Research and Development Program of Science and Technology Department of Sichuan Province(No.2019YFS0514)Funds for the Construction of Master’s Degree Granting Units in Guangxi Zhuang Autonomous Region in 2020 for the support。
文摘Niobium carbide MXene quantum dots(Nb2 C MQDs)derived from 2 D Nb2 CTx(MXene)are the rising-star material recently.Herein,a sulfur and nitrogen co-doped Nb2 C MQDs(S,N-MQDs)were synthesized through a hydrothermal method.The obtained Nb2 C MQDs have excellent green fluorescence with a quantum yield(QY)of 17.25%.In addition,they exhibited excitatio n-dependent photoluminescence,antiphotobleaching and dispersion stability.They emit light at 520 nm when excited at 390 nm.The Nb2 C MQDs could be successfully applied to copper ion detection with detection limit of 2μmol/L and Caco-2 cells imaging.
基金National Natural Science Foundation of China(Nos.82171030,81870678)Natural Science Foundation of Hunan Province,China(No.2021JJ30925)+1 种基金Health Commission of Hunan Province,China(No.B202307026146)Natural Science Foundation of Hainan Province,China(No.821QN1005)。
基金financially supported by the Science and Technology Department of Guangxi Zhuang Autonomous(No.GuiKeAD21238022)the National Natural Science Foundation of China(Nos.52001079,22379030 and 52261038)Quzhou Science and Technology Project(No.2022K103)。
文摘The Li-Mg-B-H composite(2LiBH_(4)+MgH_(2))has a high capacity of 11.4 wt%as a hydrogen storage material.However,the slow kinetics and poor cycling stability severely restrict its practical applications.In this work,a layered Nb_(2)C MXene was first synthesized and then introduced to tailor the kinetics and cycling stability of the Li-Mg-B-H composite.The milled 2LiH+MgB_(2)composites were initially hydrogenated to obtain the 2LiBH_(4)+MgH_(2)composites.The 2LiBH_(4)+MgH_(2)+5wt%Nb_(2)C can release 9.0 wt%H_(2)in 30 min at 400℃,while it is only 2.7 wt%for the undoped 2LiBH_(4)+MgH_(2).The dehydrogenation activation energies of MgH_(2)and LiBH_(4)are 123 and 154 kJ·mol^(-1)respectively for the 5 wt%Nb_(2)C-doped composite,lower than the undoped composite(164 and 165 kJ·mol^(-1)).The 2LiBH_(4)+MgH_(2)+5 wt%Nb_(2)C possesses excellent cycling stability,with the reversible capacity only slightly reduced from 9.4 wt%for the 1st cycle to 9.3 wt%for the 20th cycle.Nb_(2)C keeps stable in the composite and acts as an efficient catalyst for the Li-Mg-B-H composite.It is believed that both the layered structure and the active Nb element contribu te to the enhanced hydrogen storage performances of the Li-Mg-B-H composite.This work confirms that the Nb_(2)C MXene with layered stru cture has a significant enhancing impact on the Li-Mg-B-H hydrogen storage materials,which is different from the bulk NbC.
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 National Natural Science Foundation of China(51775540)Zhejiang Provincial Natural Science Foundation of China(LR21E050001)the Youth Innovation Promotion Association,CAS(2017338).
文摘Novel two-dimensional(2D)Nb_(2)C nanosheets were successfully prepared through a simple lultrasonic and magnetic stirring treatment from the original accordion-like powder.To further study their water-lubrication properties and deal with common oxidation problems,Nb_(2)C nanosheets with different oxidation degrees were prepared and achieved long-term stability in deionized water.Scanning electron microscope(SEM),transmission electron microscope(TEM),scanning probe microscope(SPM),X-ray powder diffraction(XRD),Raman,and X-ray photoelectron spectrometer(XPS)experiments were utilized to characterize the structure,morphology,and dispersion of Nb_(2)C nanosheets with different degrees of oxidation.The tribological behaviors of Nb_(2)C with different degrees of oxidation as additives for water lubrication were characterized using a UMT-3 friction testing machine.The wear scars formed on the 316 steel surface were measured using three-dimensional(3D)laser scanning confocal microscopy.The tribological results showed that a moderately oxidized Nb_(2)C nanosheet,which owned the composition of Nb_(2)C/Nb_(2)O5/C,displayed excellent tribological performance,with the friction coefficient(COF)decreasing by 90.3%and a decrease in the wear rate by 73.1%compared with pure water.Combining the TEM and Raman spectra,it was shown that Nb_(2)O5 nanoparticles filled in the worn zone,and the layered Nb_(2)C and C were adsorbed into the surface of the friction pair to form a protective lubricating film.This combined action resulted in an excellent lubricating performance.
基金supported by Natural Science Foundation of Hebei Province of China(Nos.B2021202028,B2020202052,B2019202277)Outstanding Youth Project of Guangdong Natural Science Foundation(No.2021B1515020051)+9 种基金State Key Laboratory of Reliability and Intelligence of Electrical Equipment(No.EERI_PI2020007)Hebei University of Technology,Chinathe Program for the Outstanding Young Talents of Hebei Province,China(YG.Z.)Chunhui Project of Ministry of Education of the People’s Republic of China(No.Z2017010)Department of Science and Technology of Guangdong Province(Nos.2020B0909030004,2019JC01L203)Guangdong Innovative and Entrepreneurial Team Program(No.2016ZT06C517)Science and Technology Program of Guangzhou(No.2019050001)Science and Technology Program of Zhaoqing(No.2019K038)project AP09259764“Engineering of Multifunctional Materials of Next Generation Batteries”from the Ministry of Education and Science of Kazakhstana research project FDCRP No.110119FD4504“Development of 3D solid state thin film materials for durable and safe Li-ion microbatteries”from Nazarbayev University。
文摘Extensive research has been devoted to lithium-sulfur(Li-S)batteries due to their overwhelming promises and advantages such as high theoretical capacity(1675 m Ah g^(-1)),extremely cost effectiveness and abundance and availability of sulfur.Nevertheless,a sluggish electrochemical kinetics of the battery limited by a slow conversion of lithium polysulfide(LiPSs)intermediates and Li PSs shuttle effect severely hinder its development towards industrial application.Herein,we designed the oxidized Nb2_(C)MXene with amorphous carbon(Nb_(2)O_(5)/C)composites as sulfur host using CO_(2)treatment to address the above issues.The Nb_(2)O_(5)/C composites with high conductivity are directly employed as sulfur hosts for Li-S battery capable to remarkably mitigate the shuttle phenomenon due to a combined effect of their Li PSs trapping ability and catalytic activity towards their accelerated conversion.Meanwhile,the unique layered structure of the composite facilitates ion transfer and accommodates the volume changes of the cathode during cycling.With this rational design,the resultant Li-S batteries exhibit superior electrochemical performance with a high initial specific capacity of 745 m Ah g^(-1)at 1.0 C and a reversible capacity of 620 m Ah g^(-1)at a high rate cycling at 3.0 C.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. U1804130, U2004212, 11904084, and 11874141)the Henan Overseas Expertise Introduction Center for Discipline Innovation (Grant No. CXJD2019005)+1 种基金the China Postdoctoral Science Foundation (Grant No. 2021M690933)the Key Scientific Research Projects of Henan Education Department, China (Grant No. 22A140020)。
文摘MXenes are a new type of two-dimensional carbides with rich physical and chemical properties. The physics of MXenes, and thus the applications, are dominated by surface functional groups. Herein, the effects of different terminations(O,S, Se, Te) on the geometric and electronic properties of Nb_(2)C MXenes were studied via density functional theory(DFT)calculations. Three adsorption sites were examined to determine the most stable configurations. The results showed that both the types and the positions of surface functional groups influence the geometric stability and physical characters of Nb_(2)C. The S and Se terminations make the Nb_(2)C MXenes to be semiconductor, while Nb_(2)C MXenes with other terminations(O, Te) are conductor. The electron location function, density of states, Bader charge distribution, and the projected crystal orbital Hamilton population were conducted to explain the origin of adsorption stability and electronic nature difference. Our results provide a fundamental understanding about the effects of surface terminations on the intrinsic stability and electronic properties of Nb_(2)C MXenes.
