Uniform Fe3 C/N-doped carbon nanofibers were successfully synthesized through a facile self-catalyzed CVD method by using acetylene as carbon source and Fe3O4 as iron source and autocatalytic template for the reaction...Uniform Fe3 C/N-doped carbon nanofibers were successfully synthesized through a facile self-catalyzed CVD method by using acetylene as carbon source and Fe3O4 as iron source and autocatalytic template for the reaction under moderate preparation conditions. The experimental and theoretical calculation results demonstrate that Fe3 C can improve the lithium storage performance of carbon nanofibers. Besides, the addition of PPy can not only control the growth rate of carbon fibers but also help to form uniform carbon fibers. As a result, the obtained Fe3 C/N-doped carbon nanofiber composites display favorable electrochemical performance as an anode for lithium-ion batteries, which including satisfactory rate performance of 402 m A h g-1 under 1.2 Ag-1, and good cycling stability of 502.3 m A h g-1 under 200 m Ag-1 over 400 cycles. The introduction of Fe3 C species and the uniform carbon fiber morphology are responsible for the long-cycling and high rate performance of materials.展开更多
The main results obtained from the experimental and engineering investigation on the heat evolution and cracking risk of a furnace concrete block were presented. The heat evolution of experimental mortars containing m...The main results obtained from the experimental and engineering investigation on the heat evolution and cracking risk of a furnace concrete block were presented. The heat evolution of experimental mortars containing micro-slag under different environmental temperatures was instrumented in order to investigate the self-catalyzed effect, which was discovered in engineering. More-over,the thermal stress of the furnace concrete due to heat temperature rise was calculated to evaluate the cracking risk of mass concrete containing micro-slag due to self-catalyzed effect. The experimental results illustrate that with the development of hydration and initial temperature of mixture, the hydra-tion can be also accelerated and temperature of concrete will be continued to rise, which was the self-catalyzed effect. And the thermal stress due to self-catalyzed effect could not result in the cracking of furnace concrete.展开更多
A novel naphthyl-based self-catalyzed phthalonitrile monomer was prepared via nucleophilic displacement reaction. The structure was characterized by Fourier infrared spectrum （FT-IR） and nuclear magnetic resonance ...A novel naphthyl-based self-catalyzed phthalonitrile monomer was prepared via nucleophilic displacement reaction. The structure was characterized by Fourier infrared spectrum （FT-IR） and nuclear magnetic resonance （^1H NMR）. The polymerization mechanism was explored. Thermal properties were characterized by differential scanning calorimetry （DSC） and thermogravimetric analysis （TGA）, which demonstrated self-promoted behavior and excellent heat resistance.展开更多
Designing cost-effective and high-performance carbon-based oxygen reduction reaction(ORR)electrocatalysts is crucial in the development of Zn-air batteries(ZABs).In this study,a facile one-pot synthesis approach is en...Designing cost-effective and high-performance carbon-based oxygen reduction reaction(ORR)electrocatalysts is crucial in the development of Zn-air batteries(ZABs).In this study,a facile one-pot synthesis approach is engineered to construct Zn/Co-N-C carbonaceous polyhedrons interconnected with self-catalyzed-grown carbon nanotubes(CNTs)from zeolitic imidazolium frameworks linked with graphene oxide nanosheets.The special N-doped threedimensional(3 D)carbon matrix allows manipulating the exposure of active sites and the synergistic interaction between metal nanoparticles and CNTs.The as-synthesized catalyst features impressive ORR activity in 0.1 mol L^(-1)KOH(E_(1/2)=0.83 V)and 0.5 mol L^(-1)H_(2)SO_(4)(E_(1/2)=0.73 V),satisfactory cycling stability and methanol resistance comparable to those of the benchmark Pt/C catalyst(E_(1/2)=0.80 V in 0.1 mol L^(-1)KOH,E_(1/2)=0.75 V in 0.5 mol L^(-1)H_(2)SO_(4)).Furthermore,the asestablished ZAB demonstrates a competitive peak power density(90 mW cm^(-2))and prominent long-term stability,which are better than those of devices based on the commercial Pt/C catalyst(82 mW cm^(-2)).This work provides promising guidance for fabricating highly effective ORR catalysts with in situ formed CNTs,which can be applied in portable ZABrelated devices.展开更多
The effect of Sb addition on the morphology of self-catalyzed InAsSb nanowires （NWs） has been systematically investigated. InAs NWs were grown by molecular beam epitaxy with and without antimony （Sb） flux. It is d...The effect of Sb addition on the morphology of self-catalyzed InAsSb nanowires （NWs） has been systematically investigated. InAs NWs were grown by molecular beam epitaxy with and without antimony （Sb） flux. It is demonstrated that trace amounts of Sb flux are capable of tuning the geometry of NWs, i.e., enhancing lateral growth and suppressing axial growth. We attribute this behavior to the surfactant effect of Sb which results in modifications to the kinetic and thermodynamic processes. A thermodynamic mechanism that accounts for Sb segregation in InAsSb NWs is also elucidated. This study opens a new route towards precisely controlled NW geometries by means of Sb addition.展开更多
The oxygen reduction reaction(ORR),an important process in Zn-air batteries(ZABs),shows sluggish reaction kinetics,which significantly impairs the further improvement of battery performance.Thus,rationally designing c...The oxygen reduction reaction(ORR),an important process in Zn-air batteries(ZABs),shows sluggish reaction kinetics,which significantly impairs the further improvement of battery performance.Thus,rationally designing cathodic catalysts for ZABs has drawn sufficient attention.We herein synthesize and characterize Fe/N/F-tridoped CNTs(FeNFCs)by annealing the postsynthesized trifluoroacetic anhydridemodified Fe-MIL-88B-NH_(2)nanocrystals with melamine at high temperature in a N_(2)atmosphere.Benefiting from the Fe/N/F element doping,high specific surface area,and CNT structure,the FeNFC800 catalyst prepared at 800℃exhibits a preferable half-wave potential of 0.829 V vs.RHE.The Zn-air battery equipped with Fe NFC800 shows a high open-circuit voltage of 1.47 V,a gratifying peak power density of196 mW/cm^(2),and extraordinary long-term stability,outperforming the benchmark 20%Pt/C.展开更多
Fe-N_x sites have been identified as core descriptors for Fe-N/C based oxygen reduction reaction catalysts.However, the low density and less utilization of Fe-Nxsites render these catalysts with inefficient catalytic ...Fe-N_x sites have been identified as core descriptors for Fe-N/C based oxygen reduction reaction catalysts.However, the low density and less utilization of Fe-Nxsites render these catalysts with inefficient catalytic performance. Herein, we develop an organic carboxylate-assisted engineering to construct Fe, N co-doped porous carbon interlinked carbon nanotubes(Fe/N-CCNTs) with high-density and sufficiently exposed FeNxsites based on self-catalyzed effect. The existing forms of Fe include Fe-imidazole configuration and coordination with unsaturated Zn sites via organic carboxylate as linkers, leading to high-density Fe-N_x sites after pyrolysis. Besides, hexatomic carbon rings of organic carboxylate lower cyclization energy barrier for CNT formation, resulting in CNTs interlinked with separated active sites through “active pointconductive line-active point” connections. The optimal sample(Fe-BOAc-PNC) exhibits the onset potential of 0.93 V(vs. RHE) and half-wave potential of 0.84 V in alkaline solution. The liquid-state Zn-air battery(ZAB) employing Fe-BOAc-PNC generates large power density(160 m W/cm^(2)) and stability over 160 h.Moreover, the assembled flexible ZAB displays superb power density of 93 m W/cm^(2) with robust flexibility. This work provides an insightful perspective for designing Fe-N/C catalysts with high-density and sufficiently exposed active sites for energy storage application.展开更多
The self-catalyzed growth of Ga As nanowires(NWs)on silicon(Si)is an effective way to achieve integration between group III–V elements and Si.High-crystallinity uniform Ga As NW arrays were grown by solid-source mole...The self-catalyzed growth of Ga As nanowires(NWs)on silicon(Si)is an effective way to achieve integration between group III–V elements and Si.High-crystallinity uniform Ga As NW arrays were grown by solid-source molecular beam epitaxy(MBE).In this paper,we describe systematic experiments which indicate that the substrate treatment is crucial to the highly crystalline and uniform growth of one-dimensional nanomaterials.The influence of natural oxidation time on the crystallinity and uniformity of Ga As NW arrays was investigated and is discussed in detail.The Ga As NW crystallinity and uniformity are maximized after 20 days of natural oxidation time.This work provides a new solution for producing high-crystallinity uniform III–V nanowire arrays on wafer-scale Si substrates.The highly crystalline uniform NW arrays are expected to be useful for NW-based optical interconnects and Si platform optoelectronic devices.展开更多
Simultaneous epitaxial growth of film and nanowire array on a substrate is of both scientific significance and practical importance for nanoscale optoelectronics. Nevertheless, in situ building conducting connection b...Simultaneous epitaxial growth of film and nanowire array on a substrate is of both scientific significance and practical importance for nanoscale optoelectronics. Nevertheless, in situ building conducting connection between individually isolated nanowires grown on insulating substrates is still challenging. Herein, we demonstrate a novel and facile strategy for the simultaneous epitaxial growth of nonpolar a-plane ZnO film and obliquely aligned nanowire array on Au-coated r-plane sapphire substrate. The morphology, structure, components, and optical properties of the as-synthesized ZnO nanostructures were investigated using field-emission scanning electron microscopy X-ray diffraction, field-emission transmission electron microscopy energy-dispersive spectroscopy, X-ray photo- electron spectroscopy, and photoluminescence spectroscopy. A cooperative growth mechanism is proposed： Au-catalyzed vapor transport initiates the co-occurrence of nonpolar a-plane and polar c-plane ZnO nuclei, and subsequently, the non-upward directed Au catalyst helps the nonpolar a-plane ZnO nuclei develop into a ZnO conductive film at the bottom and zinc self-catalyzed vapor-liquid-solid growth helps the polar c-plane ZnO nuclei develop simultaneously into obliquely aligned nanowire arrays. The proposed strategy realized in situ synthesis of nanowires with conductive connection and it can benefit the application of ZnO nanowires in optoelectronics.展开更多
A CMOS compatible process is prese nted in order to grow self-catalyzed InAs nano wires on silic on by molecular beam epitaxy. The crucial step of this process is a new in-situ surface preparation under hydrogen (gas ...A CMOS compatible process is prese nted in order to grow self-catalyzed InAs nano wires on silic on by molecular beam epitaxy. The crucial step of this process is a new in-situ surface preparation under hydrogen (gas or plasma) during the substrate degassing combined with an in-situ arsenic ann eali ng prior to growth. Morphological and structural characterizati ons of the InAs nano wires are prese nted and growth mecha nisms are discussed in detail. The major in flue nee of surface termi nation is exposed both experime ntally and theoretically using statistics on ensemble of nanowires and density functional theory (DFT) calculations. The differences observed between Molecular Beam Epitaxy (MBE) and Metal Organic Vapor Phase Epitaxy (MOVPE) growth of I nAs nano wires can be explai ned by these differe nt surfaces termi nations. The transition between a vapor solid (VS) and a vapor liquid solid (VLS) growth mechanism is presented. Optimized growth conditions lead to very high aspect ratio nano wires (up to 50 nm in diameter and 3 micron in len gth) without passi ng the 410℃ thermal limit, which makes the whole process CMOS compatible. Overall, our results suggest a new method for surface preparation and a possible tuning of the growth mechanism using different surface termi nations.展开更多
基金This research is supported by the National Natural Science Foundation of China(Grant Nos.51772092,51972109 and 51804116)the Natural Science Foundation ofHunanProvince,China(Grant No.2019JJ50205)+1 种基金the Scientific Research Foundation of Hunan Provincial Education Department,China(Grant Nos.18A315,18B347 and 18B346)the Hunan Provincial Innovation Foundation for Postgraduate(Grant No.CX2018B773).
文摘Uniform Fe3 C/N-doped carbon nanofibers were successfully synthesized through a facile self-catalyzed CVD method by using acetylene as carbon source and Fe3O4 as iron source and autocatalytic template for the reaction under moderate preparation conditions. The experimental and theoretical calculation results demonstrate that Fe3 C can improve the lithium storage performance of carbon nanofibers. Besides, the addition of PPy can not only control the growth rate of carbon fibers but also help to form uniform carbon fibers. As a result, the obtained Fe3 C/N-doped carbon nanofiber composites display favorable electrochemical performance as an anode for lithium-ion batteries, which including satisfactory rate performance of 402 m A h g-1 under 1.2 Ag-1, and good cycling stability of 502.3 m A h g-1 under 200 m Ag-1 over 400 cycles. The introduction of Fe3 C species and the uniform carbon fiber morphology are responsible for the long-cycling and high rate performance of materials.
基金Funded by the Key Technologies R&D Program from Department of Science and Technology Hubei Province(200410G0121) "973" Pro-gram(001CB610704-3) from Ministry of Science and Technology of China
文摘The main results obtained from the experimental and engineering investigation on the heat evolution and cracking risk of a furnace concrete block were presented. The heat evolution of experimental mortars containing micro-slag under different environmental temperatures was instrumented in order to investigate the self-catalyzed effect, which was discovered in engineering. More-over,the thermal stress of the furnace concrete due to heat temperature rise was calculated to evaluate the cracking risk of mass concrete containing micro-slag due to self-catalyzed effect. The experimental results illustrate that with the development of hydration and initial temperature of mixture, the hydra-tion can be also accelerated and temperature of concrete will be continued to rise, which was the self-catalyzed effect. And the thermal stress due to self-catalyzed effect could not result in the cracking of furnace concrete.
基金supported by Program for Changjiang Scholars and Innovative Research Team in University (No.IRT13060)the financial support from Natural Science Foundation of Hebei Province (No.E2014202033)
文摘A novel naphthyl-based self-catalyzed phthalonitrile monomer was prepared via nucleophilic displacement reaction. The structure was characterized by Fourier infrared spectrum （FT-IR） and nuclear magnetic resonance （^1H NMR）. The polymerization mechanism was explored. Thermal properties were characterized by differential scanning calorimetry （DSC） and thermogravimetric analysis （TGA）, which demonstrated self-promoted behavior and excellent heat resistance.
基金supported by the National Natural Science Foundation of China(51872076 and U1804255)the Program for Innovative Research Team of Henan Scientific Committee(CXTD2014033)+1 种基金the Project of Central Plains Science and Technology Innovation Leading Talents of Henan Province(194200510001)the Scientific and Technological Research Project of Henan province(212102210651)。
文摘Designing cost-effective and high-performance carbon-based oxygen reduction reaction(ORR)electrocatalysts is crucial in the development of Zn-air batteries(ZABs).In this study,a facile one-pot synthesis approach is engineered to construct Zn/Co-N-C carbonaceous polyhedrons interconnected with self-catalyzed-grown carbon nanotubes(CNTs)from zeolitic imidazolium frameworks linked with graphene oxide nanosheets.The special N-doped threedimensional(3 D)carbon matrix allows manipulating the exposure of active sites and the synergistic interaction between metal nanoparticles and CNTs.The as-synthesized catalyst features impressive ORR activity in 0.1 mol L^(-1)KOH(E_(1/2)=0.83 V)and 0.5 mol L^(-1)H_(2)SO_(4)(E_(1/2)=0.73 V),satisfactory cycling stability and methanol resistance comparable to those of the benchmark Pt/C catalyst(E_(1/2)=0.80 V in 0.1 mol L^(-1)KOH,E_(1/2)=0.75 V in 0.5 mol L^(-1)H_(2)SO_(4)).Furthermore,the asestablished ZAB demonstrates a competitive peak power density(90 mW cm^(-2))and prominent long-term stability,which are better than those of devices based on the commercial Pt/C catalyst(82 mW cm^(-2)).This work provides promising guidance for fabricating highly effective ORR catalysts with in situ formed CNTs,which can be applied in portable ZABrelated devices.
文摘The effect of Sb addition on the morphology of self-catalyzed InAsSb nanowires （NWs） has been systematically investigated. InAs NWs were grown by molecular beam epitaxy with and without antimony （Sb） flux. It is demonstrated that trace amounts of Sb flux are capable of tuning the geometry of NWs, i.e., enhancing lateral growth and suppressing axial growth. We attribute this behavior to the surfactant effect of Sb which results in modifications to the kinetic and thermodynamic processes. A thermodynamic mechanism that accounts for Sb segregation in InAsSb NWs is also elucidated. This study opens a new route towards precisely controlled NW geometries by means of Sb addition.
基金the financial supports from National Natural Science Foundation of China(Nos.21971077,22071070)the facility support of the Center for Nanoscale Characterization&Devices(CNCD),WNLO of HUST,and the Analytical and Testing Center in Huazhong University of Science and Technology for all related measurements。
文摘The oxygen reduction reaction(ORR),an important process in Zn-air batteries(ZABs),shows sluggish reaction kinetics,which significantly impairs the further improvement of battery performance.Thus,rationally designing cathodic catalysts for ZABs has drawn sufficient attention.We herein synthesize and characterize Fe/N/F-tridoped CNTs(FeNFCs)by annealing the postsynthesized trifluoroacetic anhydridemodified Fe-MIL-88B-NH_(2)nanocrystals with melamine at high temperature in a N_(2)atmosphere.Benefiting from the Fe/N/F element doping,high specific surface area,and CNT structure,the FeNFC800 catalyst prepared at 800℃exhibits a preferable half-wave potential of 0.829 V vs.RHE.The Zn-air battery equipped with Fe NFC800 shows a high open-circuit voltage of 1.47 V,a gratifying peak power density of196 mW/cm^(2),and extraordinary long-term stability,outperforming the benchmark 20%Pt/C.
基金supported by the National Natural Science Foundation of China (No. U1804255)the Key Research & Development and Promotion Projects in Henan Province (Nos. 222102520038 and 212102210651)。
文摘Fe-N_x sites have been identified as core descriptors for Fe-N/C based oxygen reduction reaction catalysts.However, the low density and less utilization of Fe-Nxsites render these catalysts with inefficient catalytic performance. Herein, we develop an organic carboxylate-assisted engineering to construct Fe, N co-doped porous carbon interlinked carbon nanotubes(Fe/N-CCNTs) with high-density and sufficiently exposed FeNxsites based on self-catalyzed effect. The existing forms of Fe include Fe-imidazole configuration and coordination with unsaturated Zn sites via organic carboxylate as linkers, leading to high-density Fe-N_x sites after pyrolysis. Besides, hexatomic carbon rings of organic carboxylate lower cyclization energy barrier for CNT formation, resulting in CNTs interlinked with separated active sites through “active pointconductive line-active point” connections. The optimal sample(Fe-BOAc-PNC) exhibits the onset potential of 0.93 V(vs. RHE) and half-wave potential of 0.84 V in alkaline solution. The liquid-state Zn-air battery(ZAB) employing Fe-BOAc-PNC generates large power density(160 m W/cm^(2)) and stability over 160 h.Moreover, the assembled flexible ZAB displays superb power density of 93 m W/cm^(2) with robust flexibility. This work provides an insightful perspective for designing Fe-N/C catalysts with high-density and sufficiently exposed active sites for energy storage application.
基金the National Natural Science Foundation of China(Grant Nos.61674021,11674038,61704011,61904017,11804335,and 12074045)the Developing Project of Science and Technology of Jilin Province,China(Grant No.20200301052RQ)+1 种基金the Project of Education Department of Jilin Province,China(Grant No.JJKH20200763KJ)the Youth Foundation of Changchun University of Science and Technology(Grant No.XQNJJ-2018-18)。
文摘The self-catalyzed growth of Ga As nanowires(NWs)on silicon(Si)is an effective way to achieve integration between group III–V elements and Si.High-crystallinity uniform Ga As NW arrays were grown by solid-source molecular beam epitaxy(MBE).In this paper,we describe systematic experiments which indicate that the substrate treatment is crucial to the highly crystalline and uniform growth of one-dimensional nanomaterials.The influence of natural oxidation time on the crystallinity and uniformity of Ga As NW arrays was investigated and is discussed in detail.The Ga As NW crystallinity and uniformity are maximized after 20 days of natural oxidation time.This work provides a new solution for producing high-crystallinity uniform III–V nanowire arrays on wafer-scale Si substrates.The highly crystalline uniform NW arrays are expected to be useful for NW-based optical interconnects and Si platform optoelectronic devices.
基金This work was funded by Hundred Talents Program of Fujian Province and the National Natural Science Foundation of China （No. 61774158）, and the Natural Science Foundation of Fujian Province （No. 2018J01110）.
文摘Simultaneous epitaxial growth of film and nanowire array on a substrate is of both scientific significance and practical importance for nanoscale optoelectronics. Nevertheless, in situ building conducting connection between individually isolated nanowires grown on insulating substrates is still challenging. Herein, we demonstrate a novel and facile strategy for the simultaneous epitaxial growth of nonpolar a-plane ZnO film and obliquely aligned nanowire array on Au-coated r-plane sapphire substrate. The morphology, structure, components, and optical properties of the as-synthesized ZnO nanostructures were investigated using field-emission scanning electron microscopy X-ray diffraction, field-emission transmission electron microscopy energy-dispersive spectroscopy, X-ray photo- electron spectroscopy, and photoluminescence spectroscopy. A cooperative growth mechanism is proposed： Au-catalyzed vapor transport initiates the co-occurrence of nonpolar a-plane and polar c-plane ZnO nuclei, and subsequently, the non-upward directed Au catalyst helps the nonpolar a-plane ZnO nuclei develop into a ZnO conductive film at the bottom and zinc self-catalyzed vapor-liquid-solid growth helps the polar c-plane ZnO nuclei develop simultaneously into obliquely aligned nanowire arrays. The proposed strategy realized in situ synthesis of nanowires with conductive connection and it can benefit the application of ZnO nanowires in optoelectronics.
文摘A CMOS compatible process is prese nted in order to grow self-catalyzed InAs nano wires on silic on by molecular beam epitaxy. The crucial step of this process is a new in-situ surface preparation under hydrogen (gas or plasma) during the substrate degassing combined with an in-situ arsenic ann eali ng prior to growth. Morphological and structural characterizati ons of the InAs nano wires are prese nted and growth mecha nisms are discussed in detail. The major in flue nee of surface termi nation is exposed both experime ntally and theoretically using statistics on ensemble of nanowires and density functional theory (DFT) calculations. The differences observed between Molecular Beam Epitaxy (MBE) and Metal Organic Vapor Phase Epitaxy (MOVPE) growth of I nAs nano wires can be explai ned by these differe nt surfaces termi nations. The transition between a vapor solid (VS) and a vapor liquid solid (VLS) growth mechanism is presented. Optimized growth conditions lead to very high aspect ratio nano wires (up to 50 nm in diameter and 3 micron in len gth) without passi ng the 410℃ thermal limit, which makes the whole process CMOS compatible. Overall, our results suggest a new method for surface preparation and a possible tuning of the growth mechanism using different surface termi nations.
