Selective oxidation of 5-hydroxymethylfurfual(HMF) to 2,5-furandicarboxylic acid(FDCA) as a bioplastics monomer is efficiently promoted by a simple system without noble-metal and base additives. In this work, graphene...Selective oxidation of 5-hydroxymethylfurfual(HMF) to 2,5-furandicarboxylic acid(FDCA) as a bioplastics monomer is efficiently promoted by a simple system without noble-metal and base additives. In this work, graphene oxide(GO) was first synthesised by an electrochemical method with flexible graphite paper(FGP) as start carbon material, then, nitrogen-doped graphene(NG) layers encapsulated Cu nanoparticles(NPs) was prepared by one-step thermal treatment of GO supported Cu2+ in flowing NH3 atmosphere. Compared with NG supported Cu NPs prepared by the traditional impregnation method, enhanced catalytic activity was achieved over Cu/NG and an FDCA yield of 95.2% was achieved under mild reaction conditions with tert-butylhydroperoxide(t-BuOOH) as the oxidant. Control experiments with different catalysts and different addition procedure of t-BuOOH showed the yield of HMF and various intermediates during reaction. From the changing of intermediates concentrations and reaction rates, a reaction pathway through HMF-DFF-FFCA-FDCA was proposed. This work gives a more convenient, more green,more economical and effective method in encapsulated metal NPs preparation and high selectivity in HMF oxidation to FDCA under mild conditions.展开更多
A novel and efficient route for preparing carbon encapsulated metal nanomaterials using staple biopolymer-starch as the carbon precursor was presented. Fe particles can be effectively encapsulated inside carbon shells...A novel and efficient route for preparing carbon encapsulated metal nanomaterials using staple biopolymer-starch as the carbon precursor was presented. Fe particles can be effectively encapsulated inside carbon shells by carbonizing composite of starch and iron oxide under hydrogen in a controllable way. Transmission electron microscopy (TEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) were employed to characterize carbon encapsulated nanomaterials. The α-Fe and γ-Fe phases were clearly identified in those carbon encapsulated nanoparticles. The growth mechanism of carbon encapsulated metal nanoparticles was briefly discussed.展开更多
The graphite encapsulated a-Fe particles were prepared by reduction of stage-2 and stage-3 FeCI3 graphite intercalation compounds （GICs） with metallic potassium, X-ray diffraction analysis （XRD）, energy dispersive...The graphite encapsulated a-Fe particles were prepared by reduction of stage-2 and stage-3 FeCI3 graphite intercalation compounds （GICs） with metallic potassium, X-ray diffraction analysis （XRD）, energy dispersive X-ray spectroscopy （EDS） investigation and transmission electron microscopy （TEM） observation show that the reduction products of stage-2 FeCl3-GICs contains more abundant a-Fe nanoparticles than those of stage-3. High-resolution TEM （HRTEM） observation reveals that the nanoparticle of a-Fe was polycrystals or twins, which was real or quasi two-dimension in shape, and whose space orientation was strictly controlled by the graphene. Based on the experiment results, a possible growth model of the graphite encapsulated ct-Fe was proposed.展开更多
Carbon encapsulated magnetic nanoparticles （CEMNs） were synthesized by heating an aqueous glucose solution containing Fe-Au （Au coated Fe nanoparticles） nanoparticles at 160-180 ℃ for 2 h. This novel hydrothermal...Carbon encapsulated magnetic nanoparticles （CEMNs） were synthesized by heating an aqueous glucose solution containing Fe-Au （Au coated Fe nanoparticles） nanoparticles at 160-180 ℃ for 2 h. This novel hydrothermal approach is not only simple but also provides the surface of CEMNs with functional groups like--OH. The formation of carbon encapsulated magnetic nanoparticles was not favored when using pure Fe nanoparticles as cores because of the oxidation of Fe nanoparticles by 1-120 during the reaction and, therefore, the surfaces of the naked Fe nanoparticles had to be coated by Au shell in advance. TEM, XRD, XPS and VSM measurments characterized that they were uniform carbon spheres containing some embedded Fe-Au nanoparticles, with a saturation of 14.6 emu/g and the size of the typical product is -350 nm.展开更多
Carbon encapsulated iron nanoparticles （CEINPs） with very thin shells and good core-shell structures were prepared by DC arc discharge at argon intake temperature （AIT） of 800 ℃. The results of high resolution tr...Carbon encapsulated iron nanoparticles （CEINPs） with very thin shells and good core-shell structures were prepared by DC arc discharge at argon intake temperature （AIT） of 800 ℃. The results of high resolution transmission electron microscope （HRTEM）, energy dispersive X-ray （EDX） spectroscope, X-ray diffraction （XRD）, and X-ray photoelectron spectroscope （XPS） characterizations on the product B show that the thickness of the carbon shells of CEINPs in the product B is in the range of ca. 0.5-5.3 nm, i. e., which can be as thin as only two layers of graphite. The average diameter of the CEINPs is about 24. 7 nm. The total content of Fe element in the product B is 77.0 wt%. The saturation magnetization （Ms） and coercivity （Hc） of the product B are 107.4 emu/g and 143 Oe. resnectivelv. The formation of the CEINPs in the oroduct B is discussed briefly.展开更多
Oxidative dehydrogenation of propane with carbon dioxide(CO_(2)-ODP)characterizes the tandem dehydrogenation of propane to propylene with the reduction of the greenhouse gas of CO_(2)to valuable CO.However,the existin...Oxidative dehydrogenation of propane with carbon dioxide(CO_(2)-ODP)characterizes the tandem dehydrogenation of propane to propylene with the reduction of the greenhouse gas of CO_(2)to valuable CO.However,the existing catalyst is limited due to the poor activity and stability,which hinders its industrialization.Herein,we design the finned Zn-MFI zeolite encapsulated noble metal nanoparticles(NPs)as bifunctional catalysts(NPs@Zn-MFI)for CO_(2)-ODP.Characterization results reveal that the Zn2+species are coordinated with the MFI zeolite matrix as isolated cations and the NPs of Pt,Rh,or Rh Pt are highly dispersed in the zeolite crystals.The isolated Zn2+cations are very effective for activating the propane and the small NPs are favorable for activating the CO_(2),which synergistically promote the selective transformation of propane and CO_(2)to propylene and CO.As a result,the optimal 0.25%Rh0.50%Pt@Zn-MFI catalyst shows the best propylene yield,satisfactory CO_(2)conversion,and long-term stability.Moreover,considering the tunable synergetic effects between the isolated cations and NPs,the developed approach offers a general guideline to design more efficient CO_(2)-ODP catalysts,which is validated by the improved performance of the bifunctional catalysts via simply substituting Sn4+cations for Zn2+cations in the MFI zeolite matrix.展开更多
Nanoparticles (NPS) are considered as a new generation of compounds to improve environmental remediation and biological processes. The aim of this study is to investigate the effect of iron NPS encapsulated in porous ...Nanoparticles (NPS) are considered as a new generation of compounds to improve environmental remediation and biological processes. The aim of this study is to investigate the effect of iron NPS encapsulated in porous silica (SiO2) on the biphenyl biodegradation by Rhodococcus erythropolis T902.1 (RT902.1). The iron NPS (major iron oxide FexOy form) were dispersed in the porosity of a SiO2 support synthesized by sol-gel process. These Fe/SiO2 NPS offer a stimulating effect on the biodegradation rate of biphenyl, an organic pollutant that is very stable and water-insoluble. This positive impact of NPS on the microbial biodegradation was found to be dependent on the NPS concentration ranging from 10-6 M to 10-4 M. After 18 days of incubation the cultures containing NPS at a concentration of 10-4 M of iron improved RT902.1 growth and degraded 35% more biphenyl than those without NPS (positive control) or with the sole SiO2 particles. Though the microorganism could not interact directly with the insoluble iron NPS, the results show that about 10% and 35% of the initial 10-4 M iron NPS encapsulated in the SiO2 matrix would be incorporated inside or adsorbed on the cell surface respectively and 35% would be released in the supernatant. These results suggest that RT902.1 would produce siderophore-like molecules to attract iron from the porous silica matrix.展开更多
Lithium–sulfur batteries(LSBs)are regarded as promising candidates for the next-generation energy storage devices owing to their high-theoretical capacity(1675 mAh g^(−1))and affordable cost.However,several limitatio...Lithium–sulfur batteries(LSBs)are regarded as promising candidates for the next-generation energy storage devices owing to their high-theoretical capacity(1675 mAh g^(−1))and affordable cost.However,several limitations of LSBs such as the lithium polysulfide shuttle,large volume expansion,and low electrical conductivity of sulfur need to be resolved for practical applications.To address these limitations,herein,a multidimensional architectured hybrid(Co@CNT/nG),where Co_(3)O_(4) nanoparticles are encapsulated into threedimensional(3D)porous N-doped reduced graphene oxide interconnected with carbon nanotube(CNT)branches,is synthesized through a simple pyrolysis method.The synergistic effect achieved through the homogeneously distributed and encapsulated Co_(3)O_(4) nanoparticles,the interconnected CNT branches,and the 3D hierarchical porous structure and N-doping of Co@CNT/nG significantly suppresses the shuttle effect of lithium polysulfides and enhances the conversion redox kinetics for the improved sulfur utilization.We validate this effect through various measurements including symmetric cells,Li_(2)S nucleation,shuttle currents,Tafel slopes,diffusion coefficients,and post-mortem analyses.Importantly,Co@CNT/nG-70S-based LSB cells achieve a high-specific capacity of 1193.1 mAh g^(−1) at 0.1 C and a low capacity decay rate of 0.030%per cycle for 700 cycles at 5 C,delivering a high areal capacity of 5.62 mAh cm^(−2) even with a loading of 6.5 mg cm^(−2).展开更多
Metal nanoparticle@porous material composites have attracted increasing attention due to their excellent synergistic catalytic performance.However,it is a challenge to introduce metal nanoparticles into cavities of po...Metal nanoparticle@porous material composites have attracted increasing attention due to their excellent synergistic catalytic performance.However,it is a challenge to introduce metal nanoparticles into cavities of porous materials without agglomeration on the exterior.Despite the progress achieved,a universal approach that can integrate different kinds of metal nanoparticles and porous materials is still highly desirable.Here we report a facile and general approach to fabricating metal nanoparticle@porous materials by microwave-triggered selective heating.The microwave can pass through the non-polar solvent and act on the polar solvent in the porous materials,causing the polar solvent to be heated,vaporized,and away from the pores of porous materials.The local void produced by the escape of polar solvent facilitates non-polar solvent containing metallic precursor to be dragged into the narrow pores,followed by further reduction,resulting in the complete encapsulation of nanoparticles.A series of metal nanoparticles@porous materials,ranging from metal-organic frameworks(MOFs)to zeolites,are successfully prepared by this method and show excellent size selectivity in catalytic reactions.展开更多
Sustainable metal-air batteries demand high-efficiency,environmentally-friendly,and non-precious metal-based electrocatalysts with bifunctionality for both the oxygen reduction reaction(ORR)and oxygen evolution reacti...Sustainable metal-air batteries demand high-efficiency,environmentally-friendly,and non-precious metal-based electrocatalysts with bifunctionality for both the oxygen reduction reaction(ORR)and oxygen evolution reaction(OER).In this research,novel functional carbon nanotubes with multi-active sites including well-dispersed single-atom iron throughout the walls and encapsulated ultrafine iron nanoparticles were synthesized as an electrocatalyst(FeNP@Fe-N-C)through one-step pyrolysis of metal-organic frameworks.High-resolution synchrotron powder X-ray diffraction and X-ray absorption spectroscopy were applied to characterize the unique structure of the electrocatalyst.In comparison to the commercial Pt/C and Ru O_(2)electrodes,the newly prepared FeNP@Fe-N-C presented a superb bifunctional performance with its narrow potential difference(Egap)of 0.73 V,which is ascribed to the metallic Fe nanoparticles that boosts the adsorption and activation of oxygen on the active sites with an enhanced O_(2)adsorption capacity of 7.88 cm^(3)g^(-1)and synergistically functionalizes the iron atoms dispersed on the nanotubes.A rechargeable zinc-air battery based on FeNP@Fe-N-C exhibited a superior open-circuit voltage(1.45 V),power density(106.5 m W cm^(-2)),and stable cycling performance.The green technique developed in this work for the fabrication of functional nanotubes raises the prospect of making more efficient electrocatalysts for sustainable energy cells.展开更多
The thermal release properties of soy oil from poly（styrene-co-maleimide） nanoparticles containing 50 wt% encapsulated oil have been quantified as a function of temperature and time. The effects of dif- ferent synth...The thermal release properties of soy oil from poly（styrene-co-maleimide） nanoparticles containing 50 wt% encapsulated oil have been quantified as a function of temperature and time. The effects of dif- ferent synthesis conditions on the thermal stability of the nanoparticles and their oil release have been evaluated, i.e., by gradually increasing the amount of ammonium hydroxide used for the imidization of poly（styrene-co-maleic anhydride）. First, the intrinsic thermal properties of the oil-filled nanoparti- cles were analysed by differential scanning calorimetry, which revealed an exothermal reaction related to the oil release and a suppression of the glass transition that may be masked owing to the complex structure of the hybrid nanoparticles. The isothermal scans showed different rates of oil release after a post-imidization reaction. The oil release was better followed by dynamic mechanical analysis, which illustrated changes in visco-elastic properties expressed by the maximum in the loss factor that related to the amount of released oil. Depending on the amount of ammonium hydroxide, the oil started to release below the glass transition temperature at various rates. Thermal release profiles of the oil we re quantified by infrared and Raman spectrocopy after heating for 2 min to 6 h at 125 to 250 ℃, based on variations in oil-related and imide-related absorption bands. The oil release increased below and above the glass transition temperature, following a parabolic trend, and progressively decreased at higher ammonium hydroxide concentrations, in parallel with higher imide content and changes in imide conformation. The kinetics and mechanism of the oil release can be described by the Korsmeyer-Peppas model, suggesting a dominating diffusion mechanism that is influenced by further imidization of the polymer matrix during heating.展开更多
Poly (D,L-lactide-co-glycolide) (PLGA) is a biodegradable and biocompatible polymer material for drug deliver system. The aim of this study is to synthesize drug-loaded
The electrochemical conversion of CO_(2)-H_(2)O into CO-H_(2) using renewable energy is a promising technique for clean syngas production.Low-cost electrocatalysts to produce tunable syngas with a potential-independen...The electrochemical conversion of CO_(2)-H_(2)O into CO-H_(2) using renewable energy is a promising technique for clean syngas production.Low-cost electrocatalysts to produce tunable syngas with a potential-independent CO/H_(2) ratio are highly desired.Herein,a series of N-doped carbon nanotubes encapsulating binary alloy nanoparticles(MxNi-NCNT,M=Fe,Co)were successfully fabricated through the co-pyrolysis of melamine and metal precursors.The MxNi-NCNT samples exhibited bamboo-like nanotubular structures with a large specific surface area and high degree of graphitization.Their electrocatalytic performance for syngas production can be tuned by changing the alloy compositions and modifying the electronic structure of the carbon nanotube through the encapsulated metal nanoparticles.Consequently,syngas with a wide range of CO/H_(2) ratios,from 0.5:1 to 3.4:1,can be produced on MxNi-NCNT.More importantly,stable CO/H_(2) ratios of 2:1 and 1.5:1,corresponding to the ratio to produce biofuels by syngas fermentation,could be realized on Co1Ni-NCNT and Co2Ni-NCNT,respectively,over a potential window of-0.8 to-1.2 V versus the reversible hydrogen electrode.Our work provides an approach to develop low-cost and potential-independent electrocatalysts to effectively produce syngas with an adjustable CO/H_(2) ratio from electrochemical CO_(2) reduction.展开更多
Polymethyl methacrylate （PMMA） encapsulated silica nanocomposite particles were prepared by ultra- sonically induced in situ polymerization of methyl methacrylate （MMA） on the surface of silica sol. The nanopartic...Polymethyl methacrylate （PMMA） encapsulated silica nanocomposite particles were prepared by ultra- sonically induced in situ polymerization of methyl methacrylate （MMA） on the surface of silica sol. The nanoparticles were characterized by Fourier transform infrared spectroscopy （FFIR）, transmission electron microscopy （TEM）, thermogravimetry （TG）, scanning electron microscopy （SEM）. The results showed that core-shell structure nanocomposite particles with an average size of 36 nm were obtained, and the thickness of polymer encapsulating layer was about 8 nm. The pretreatment of silica sol with tert-butyl hydroperoxide （TBHP） and the addition of ^-methacryloxypropyl trimethoxysilane （MAPTS） significantly enhanced the encapsulation effect. Modified by the polymer layer, the silica particles could be well dispersed in matrices and utilized to improve the mechanical performance of polyacrylates.展开更多
基金the National Natural Science Foundation of China(NNSFC)(21805145&U1610108)the Department of Science and Technology of Shandong Province(ZR2019BB068)+2 种基金the Department of Science and Technology of Shanxi Province(201705D211001)Scientific and Technological Innovation Programs of High Education Institutions in Shanxi(201802001-1)the Department of Human Resource and Social Security of Shanxi Province(Y6SW9613B1)。
文摘Selective oxidation of 5-hydroxymethylfurfual(HMF) to 2,5-furandicarboxylic acid(FDCA) as a bioplastics monomer is efficiently promoted by a simple system without noble-metal and base additives. In this work, graphene oxide(GO) was first synthesised by an electrochemical method with flexible graphite paper(FGP) as start carbon material, then, nitrogen-doped graphene(NG) layers encapsulated Cu nanoparticles(NPs) was prepared by one-step thermal treatment of GO supported Cu2+ in flowing NH3 atmosphere. Compared with NG supported Cu NPs prepared by the traditional impregnation method, enhanced catalytic activity was achieved over Cu/NG and an FDCA yield of 95.2% was achieved under mild reaction conditions with tert-butylhydroperoxide(t-BuOOH) as the oxidant. Control experiments with different catalysts and different addition procedure of t-BuOOH showed the yield of HMF and various intermediates during reaction. From the changing of intermediates concentrations and reaction rates, a reaction pathway through HMF-DFF-FFCA-FDCA was proposed. This work gives a more convenient, more green,more economical and effective method in encapsulated metal NPs preparation and high selectivity in HMF oxidation to FDCA under mild conditions.
基金the National Natural Science Foundation of China (20174017)
文摘A novel and efficient route for preparing carbon encapsulated metal nanomaterials using staple biopolymer-starch as the carbon precursor was presented. Fe particles can be effectively encapsulated inside carbon shells by carbonizing composite of starch and iron oxide under hydrogen in a controllable way. Transmission electron microscopy (TEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) were employed to characterize carbon encapsulated nanomaterials. The α-Fe and γ-Fe phases were clearly identified in those carbon encapsulated nanoparticles. The growth mechanism of carbon encapsulated metal nanoparticles was briefly discussed.
基金the Natural Science Foundation of Hubei Province (No.2004ABA090)the Fund from the Chengguang Plan of Wuhan(No.20065004116-35)
文摘The graphite encapsulated a-Fe particles were prepared by reduction of stage-2 and stage-3 FeCI3 graphite intercalation compounds （GICs） with metallic potassium, X-ray diffraction analysis （XRD）, energy dispersive X-ray spectroscopy （EDS） investigation and transmission electron microscopy （TEM） observation show that the reduction products of stage-2 FeCl3-GICs contains more abundant a-Fe nanoparticles than those of stage-3. High-resolution TEM （HRTEM） observation reveals that the nanoparticle of a-Fe was polycrystals or twins, which was real or quasi two-dimension in shape, and whose space orientation was strictly controlled by the graphene. Based on the experiment results, a possible growth model of the graphite encapsulated ct-Fe was proposed.
文摘Carbon encapsulated magnetic nanoparticles （CEMNs） were synthesized by heating an aqueous glucose solution containing Fe-Au （Au coated Fe nanoparticles） nanoparticles at 160-180 ℃ for 2 h. This novel hydrothermal approach is not only simple but also provides the surface of CEMNs with functional groups like--OH. The formation of carbon encapsulated magnetic nanoparticles was not favored when using pure Fe nanoparticles as cores because of the oxidation of Fe nanoparticles by 1-120 during the reaction and, therefore, the surfaces of the naked Fe nanoparticles had to be coated by Au shell in advance. TEM, XRD, XPS and VSM measurments characterized that they were uniform carbon spheres containing some embedded Fe-Au nanoparticles, with a saturation of 14.6 emu/g and the size of the typical product is -350 nm.
文摘Carbon encapsulated iron nanoparticles （CEINPs） with very thin shells and good core-shell structures were prepared by DC arc discharge at argon intake temperature （AIT） of 800 ℃. The results of high resolution transmission electron microscope （HRTEM）, energy dispersive X-ray （EDX） spectroscope, X-ray diffraction （XRD）, and X-ray photoelectron spectroscope （XPS） characterizations on the product B show that the thickness of the carbon shells of CEINPs in the product B is in the range of ca. 0.5-5.3 nm, i. e., which can be as thin as only two layers of graphite. The average diameter of the CEINPs is about 24. 7 nm. The total content of Fe element in the product B is 77.0 wt%. The saturation magnetization （Ms） and coercivity （Hc） of the product B are 107.4 emu/g and 143 Oe. resnectivelv. The formation of the CEINPs in the oroduct B is discussed briefly.
基金supported by the National Natural Science Foundation of China(21902097,21636006 and 21761132025)the China Postdoctoral Science Foundation(2019M653861XB)+1 种基金the Natural Science Foundation of Shaanxi Province(2020JQ-409)the Fundamental Research Funds for the Central Universities(GK201901001 and GK202003035)。
文摘Oxidative dehydrogenation of propane with carbon dioxide(CO_(2)-ODP)characterizes the tandem dehydrogenation of propane to propylene with the reduction of the greenhouse gas of CO_(2)to valuable CO.However,the existing catalyst is limited due to the poor activity and stability,which hinders its industrialization.Herein,we design the finned Zn-MFI zeolite encapsulated noble metal nanoparticles(NPs)as bifunctional catalysts(NPs@Zn-MFI)for CO_(2)-ODP.Characterization results reveal that the Zn2+species are coordinated with the MFI zeolite matrix as isolated cations and the NPs of Pt,Rh,or Rh Pt are highly dispersed in the zeolite crystals.The isolated Zn2+cations are very effective for activating the propane and the small NPs are favorable for activating the CO_(2),which synergistically promote the selective transformation of propane and CO_(2)to propylene and CO.As a result,the optimal 0.25%Rh0.50%Pt@Zn-MFI catalyst shows the best propylene yield,satisfactory CO_(2)conversion,and long-term stability.Moreover,considering the tunable synergetic effects between the isolated cations and NPs,the developed approach offers a general guideline to design more efficient CO_(2)-ODP catalysts,which is validated by the improved performance of the bifunctional catalysts via simply substituting Sn4+cations for Zn2+cations in the MFI zeolite matrix.
基金the Ministry of the Walloon Region General Directorate of Technology,Resherch and Energy and the Fonds de Recherche Fondamentale Collective for financial supports
文摘Nanoparticles (NPS) are considered as a new generation of compounds to improve environmental remediation and biological processes. The aim of this study is to investigate the effect of iron NPS encapsulated in porous silica (SiO2) on the biphenyl biodegradation by Rhodococcus erythropolis T902.1 (RT902.1). The iron NPS (major iron oxide FexOy form) were dispersed in the porosity of a SiO2 support synthesized by sol-gel process. These Fe/SiO2 NPS offer a stimulating effect on the biodegradation rate of biphenyl, an organic pollutant that is very stable and water-insoluble. This positive impact of NPS on the microbial biodegradation was found to be dependent on the NPS concentration ranging from 10-6 M to 10-4 M. After 18 days of incubation the cultures containing NPS at a concentration of 10-4 M of iron improved RT902.1 growth and degraded 35% more biphenyl than those without NPS (positive control) or with the sole SiO2 particles. Though the microorganism could not interact directly with the insoluble iron NPS, the results show that about 10% and 35% of the initial 10-4 M iron NPS encapsulated in the SiO2 matrix would be incorporated inside or adsorbed on the cell surface respectively and 35% would be released in the supernatant. These results suggest that RT902.1 would produce siderophore-like molecules to attract iron from the porous silica matrix.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea Government(MSIT)(NRF-2020R1A3B2079803),Republic of Korea.
文摘Lithium–sulfur batteries(LSBs)are regarded as promising candidates for the next-generation energy storage devices owing to their high-theoretical capacity(1675 mAh g^(−1))and affordable cost.However,several limitations of LSBs such as the lithium polysulfide shuttle,large volume expansion,and low electrical conductivity of sulfur need to be resolved for practical applications.To address these limitations,herein,a multidimensional architectured hybrid(Co@CNT/nG),where Co_(3)O_(4) nanoparticles are encapsulated into threedimensional(3D)porous N-doped reduced graphene oxide interconnected with carbon nanotube(CNT)branches,is synthesized through a simple pyrolysis method.The synergistic effect achieved through the homogeneously distributed and encapsulated Co_(3)O_(4) nanoparticles,the interconnected CNT branches,and the 3D hierarchical porous structure and N-doping of Co@CNT/nG significantly suppresses the shuttle effect of lithium polysulfides and enhances the conversion redox kinetics for the improved sulfur utilization.We validate this effect through various measurements including symmetric cells,Li_(2)S nucleation,shuttle currents,Tafel slopes,diffusion coefficients,and post-mortem analyses.Importantly,Co@CNT/nG-70S-based LSB cells achieve a high-specific capacity of 1193.1 mAh g^(−1) at 0.1 C and a low capacity decay rate of 0.030%per cycle for 700 cycles at 5 C,delivering a high areal capacity of 5.62 mAh cm^(−2) even with a loading of 6.5 mg cm^(−2).
基金supported by the National Natural Science Foundation of China(Nos.21908105,21971114 and 62288102)the Nanjing Municipal Science and Technology Innovation Project.
文摘Metal nanoparticle@porous material composites have attracted increasing attention due to their excellent synergistic catalytic performance.However,it is a challenge to introduce metal nanoparticles into cavities of porous materials without agglomeration on the exterior.Despite the progress achieved,a universal approach that can integrate different kinds of metal nanoparticles and porous materials is still highly desirable.Here we report a facile and general approach to fabricating metal nanoparticle@porous materials by microwave-triggered selective heating.The microwave can pass through the non-polar solvent and act on the polar solvent in the porous materials,causing the polar solvent to be heated,vaporized,and away from the pores of porous materials.The local void produced by the escape of polar solvent facilitates non-polar solvent containing metallic precursor to be dragged into the narrow pores,followed by further reduction,resulting in the complete encapsulation of nanoparticles.A series of metal nanoparticles@porous materials,ranging from metal-organic frameworks(MOFs)to zeolites,are successfully prepared by this method and show excellent size selectivity in catalytic reactions.
基金financially supported by grants 17210219 and T21-711/16R from the Research Grants Council of the Hong Kong governmentproject 51978369 from the National Natural Science Foundation of China。
文摘Sustainable metal-air batteries demand high-efficiency,environmentally-friendly,and non-precious metal-based electrocatalysts with bifunctionality for both the oxygen reduction reaction(ORR)and oxygen evolution reaction(OER).In this research,novel functional carbon nanotubes with multi-active sites including well-dispersed single-atom iron throughout the walls and encapsulated ultrafine iron nanoparticles were synthesized as an electrocatalyst(FeNP@Fe-N-C)through one-step pyrolysis of metal-organic frameworks.High-resolution synchrotron powder X-ray diffraction and X-ray absorption spectroscopy were applied to characterize the unique structure of the electrocatalyst.In comparison to the commercial Pt/C and Ru O_(2)electrodes,the newly prepared FeNP@Fe-N-C presented a superb bifunctional performance with its narrow potential difference(Egap)of 0.73 V,which is ascribed to the metallic Fe nanoparticles that boosts the adsorption and activation of oxygen on the active sites with an enhanced O_(2)adsorption capacity of 7.88 cm^(3)g^(-1)and synergistically functionalizes the iron atoms dispersed on the nanotubes.A rechargeable zinc-air battery based on FeNP@Fe-N-C exhibited a superior open-circuit voltage(1.45 V),power density(106.5 m W cm^(-2)),and stable cycling performance.The green technique developed in this work for the fabrication of functional nanotubes raises the prospect of making more efficient electrocatalysts for sustainable energy cells.
文摘The thermal release properties of soy oil from poly（styrene-co-maleimide） nanoparticles containing 50 wt% encapsulated oil have been quantified as a function of temperature and time. The effects of dif- ferent synthesis conditions on the thermal stability of the nanoparticles and their oil release have been evaluated, i.e., by gradually increasing the amount of ammonium hydroxide used for the imidization of poly（styrene-co-maleic anhydride）. First, the intrinsic thermal properties of the oil-filled nanoparti- cles were analysed by differential scanning calorimetry, which revealed an exothermal reaction related to the oil release and a suppression of the glass transition that may be masked owing to the complex structure of the hybrid nanoparticles. The isothermal scans showed different rates of oil release after a post-imidization reaction. The oil release was better followed by dynamic mechanical analysis, which illustrated changes in visco-elastic properties expressed by the maximum in the loss factor that related to the amount of released oil. Depending on the amount of ammonium hydroxide, the oil started to release below the glass transition temperature at various rates. Thermal release profiles of the oil we re quantified by infrared and Raman spectrocopy after heating for 2 min to 6 h at 125 to 250 ℃, based on variations in oil-related and imide-related absorption bands. The oil release increased below and above the glass transition temperature, following a parabolic trend, and progressively decreased at higher ammonium hydroxide concentrations, in parallel with higher imide content and changes in imide conformation. The kinetics and mechanism of the oil release can be described by the Korsmeyer-Peppas model, suggesting a dominating diffusion mechanism that is influenced by further imidization of the polymer matrix during heating.
基金supported in part by NSFC (no. 30700151)Academic Innovation Incubation Program from UESTC (no. Y02018023601062)Some data have been published in Journal of Nanoscience and Nanotechnology (2009, 9: 282-287)
文摘Poly (D,L-lactide-co-glycolide) (PLGA) is a biodegradable and biocompatible polymer material for drug deliver system. The aim of this study is to synthesize drug-loaded
基金funded by the National Natural Science Foundation of China(Grant Nos.21873067,21206117).
文摘The electrochemical conversion of CO_(2)-H_(2)O into CO-H_(2) using renewable energy is a promising technique for clean syngas production.Low-cost electrocatalysts to produce tunable syngas with a potential-independent CO/H_(2) ratio are highly desired.Herein,a series of N-doped carbon nanotubes encapsulating binary alloy nanoparticles(MxNi-NCNT,M=Fe,Co)were successfully fabricated through the co-pyrolysis of melamine and metal precursors.The MxNi-NCNT samples exhibited bamboo-like nanotubular structures with a large specific surface area and high degree of graphitization.Their electrocatalytic performance for syngas production can be tuned by changing the alloy compositions and modifying the electronic structure of the carbon nanotube through the encapsulated metal nanoparticles.Consequently,syngas with a wide range of CO/H_(2) ratios,from 0.5:1 to 3.4:1,can be produced on MxNi-NCNT.More importantly,stable CO/H_(2) ratios of 2:1 and 1.5:1,corresponding to the ratio to produce biofuels by syngas fermentation,could be realized on Co1Ni-NCNT and Co2Ni-NCNT,respectively,over a potential window of-0.8 to-1.2 V versus the reversible hydrogen electrode.Our work provides an approach to develop low-cost and potential-independent electrocatalysts to effectively produce syngas with an adjustable CO/H_(2) ratio from electrochemical CO_(2) reduction.
文摘Polymethyl methacrylate （PMMA） encapsulated silica nanocomposite particles were prepared by ultra- sonically induced in situ polymerization of methyl methacrylate （MMA） on the surface of silica sol. The nanoparticles were characterized by Fourier transform infrared spectroscopy （FFIR）, transmission electron microscopy （TEM）, thermogravimetry （TG）, scanning electron microscopy （SEM）. The results showed that core-shell structure nanocomposite particles with an average size of 36 nm were obtained, and the thickness of polymer encapsulating layer was about 8 nm. The pretreatment of silica sol with tert-butyl hydroperoxide （TBHP） and the addition of ^-methacryloxypropyl trimethoxysilane （MAPTS） significantly enhanced the encapsulation effect. Modified by the polymer layer, the silica particles could be well dispersed in matrices and utilized to improve the mechanical performance of polyacrylates.
