Carbon-coated lithium manganese silicate （Li2MnSiO4/C） nanoparticles were synthesized by polyol process. X-ray diffraction （XRD） patterns of the obtained materials exhibit a good fit with that of the Li2MnSiO4 pha...Carbon-coated lithium manganese silicate （Li2MnSiO4/C） nanoparticles were synthesized by polyol process. X-ray diffraction （XRD） patterns of the obtained materials exhibit a good fit with that of the Li2MnSiO4 phase. Field emission scanning electron microscopy （FESEM） images of the obtained samples show that the particle size is only tens of nanometers. The high resolution transmission electron microscopy （HRTEM） analysis shows that the Li2MnSiO4 nanoparticles are surrounded by a very thin film of amorphous carbon. The composite prepared through polyol process shows good performance as cathode materials in lithium cells at room temperature. The charge capacity of the Li2MnSiO4/C samples is 219 mAh/g （about 1.3 Li^＋ per unit formula extracted）, and the discharge capacity is 132 mAh/g （about 0.8 Li^＋ per unit formula inserted） in the first cycle in the voltage range of 1.5-4.8 V. A good capacity cycling maintenance of 81.8% after 10 cycles was obtained.展开更多
A new form of Cu2O, disk-like structure with 60 nm in thickness and 2 μm in diameter,has been successfully synthesized in bulk quantities by polyol process in the presence of PVP K-30.
Polymer-protected monodisperse nickel nanoparticles were synthesized by a modified polyol reduction method in the presence of poly（N-vinyl-2-Pyrrolidone）.These nanoparticles were characterized by transmission electr...Polymer-protected monodisperse nickel nanoparticles were synthesized by a modified polyol reduction method in the presence of poly（N-vinyl-2-Pyrrolidone）.These nanoparticles were characterized by transmission electron microscopy（TEM）,X-ray diffraction（XRD）,selected area electron diffraction（SAED）,as well as vibrating sample magnetometer（VSM）.The experimental results show that the addition of PVP and the concentration of NaOh have strong influences on the size.agglomeration and uniformity of nanoparticles.In the presence of PVP and NaoH with low concentration.smonodisperse nickel nanoparticles with average diameters about 42 nm were obtained and characterized to the pure nickel crystalline with foc structure.Secondary structures such as clusters.loops.and strings resulted from magnetic interactions between particles were observed.The chemical interaction between the PVP and nickel nanoparticles was found by FTIR.The saturation magnetization（Ms）.remanent magnetization（Mr）and coercivity（Hc）of these nickel nanoparticles are lower than those of bulk nickel.展开更多
Amorphous carbon and graphene co-modified LiFePO4 nanocomposite has been synthesized via a facile polyol process in connection with a following thermal treatment.Various characterization techniques,including XRD.Mossb...Amorphous carbon and graphene co-modified LiFePO4 nanocomposite has been synthesized via a facile polyol process in connection with a following thermal treatment.Various characterization techniques,including XRD.Mossbauer spectra,Raman spectra,SEM,TEM,BET,O2-TPO,galvano charge-discharge,CV and EIS were applied to investigate the phase composition,carbon content,morphological structure and electrochemical performance of the synthesized samples.The effect of introducing way of carbon sources on the properties and performance of LiFePO4/C/graphene composite was paid special attention.Under optimized synthetic conditions,highly crystalized olivine-type LiFePO4was successfully obtained with electron conductive Fe2P and FeP as the main impurity phases.SEM and TEM analyses demonstrated the graphene sheets were randomly distributed inside the sample to create an open structured LiFePO4 with respect to graphene,while the glucosederived carbon mainly coated over LiFeP04 particles which effectively connected the graphene sheets and LiFePO4 particles to result in a more efficient charge transfer process.As a result,favorable electrochemical performance was achieved.The performance of the amorphous carbon-graphene co-modified LiFePO4 was further progressively improved upon cycling in the first 200 cycles to reach a reversible specificcapacity as high as 97 mAh·g-1 at 10 C rate.展开更多
Zinc oxide nanoparticles with different sizes and shapes have been synthesized in polyol using a bottom-up approach. We have studied the scale-up of the process to massively produce high quality nanoparticles of contr...Zinc oxide nanoparticles with different sizes and shapes have been synthesized in polyol using a bottom-up approach. We have studied the scale-up of the process to massively produce high quality nanoparticles of controlled size and shape. The scale-up strategy required the effective mixing of reagents using either axial or radial mixing configurations and was experimentally validated by comparing structural properties of particles obtained in a small and a large size reactor. In addition, the flow patterns in these reactors have been calculated using three-dimensional turbulent computational fluid dynamics (CFD) simulations. Our results indicate a strong connection between the flow patterns, as obtained by CFD simulations, and the size and shape of the particles. Actually, our pilot scale reactor allowed producing sample aliquots of ~50 grams with nanoparticle sizes ranging from 8 nm to 600 nm and aspect ratio varying from 1 (nanospheres) to 20 (nanorods). After their synthesis, these two nanoparticle classes have been tested as building blocks in D149-dye-sensitized solar cell (DSSC). The measured power conversion efficiency (PCE) was 4.66% for nanorods shaped particles and 4.21% for nanospheres. These values were significantly higher than the 3.90% PCE obtained with commercial Degussa VP20 ZnO nanoparticles.展开更多
A series of Pt/C catalysts for proton exchange membrane fuel cells(PEMFCs) with various metal loadings is synthesized by a microwave-assisted polyol process via mixing an extremely stable platinum colloid(> 3 month...A series of Pt/C catalysts for proton exchange membrane fuel cells(PEMFCs) with various metal loadings is synthesized by a microwave-assisted polyol process via mixing an extremely stable platinum colloid(> 3 months’ shelf life) from single batch preparation with activated carbon ethylene glycol suspension.21 wt%, 42 wt% and 61 wt% Pt loadings are employed to showcase the advantages of the improved polyol process. The ultraviolet(UV)–visible spectra and ζ-potential measurements are conducted to monitor the wet chemistry process during catalyst preparation. The powder X-ray diffraction(XRD), transmission electron microscopy(TEM) and thermogravimetric analysis(TGA) characterizations are carried out on catalysts. The catalyst activities are investigated using electrochemical and single cell tests. The stability of Pt nanoparticle colloid is explored by ORR, cyclic voltammetry(CV) and ζ-potential measurements. The TEM results show the Pt particle sizes of the colloid, and the sizes of the 21 wt%, 42 wt% and 61 wt%Pt/C samples are 2.1–3.9 nm. Because of the high Pt dispersion, the Pt/C catalysts exhibit superior electroactivity toward ORR. In addition, four 61 wt% Pt/C catalysts made from the Pt colloid with 0–3 months’ shelf life show almost the same performance, which exhibits superior stability of the Pt colloid system without surfactant protection.展开更多
To address the problem of fuel starvation in fuel-cell electric vehicles,which causes cell voltage reversal and results in cell failure when repeated continuously,we developed a reversal-tolerant anode(RTA) to promote...To address the problem of fuel starvation in fuel-cell electric vehicles,which causes cell voltage reversal and results in cell failure when repeated continuously,we developed a reversal-tolerant anode(RTA) to promote water oxidation in preference to carbon corrosion.Graphitized carbon-supported Ir-Ru alloys with different compositions are employed as RTA catalysts in an acidic polyol solution and are shown to exhibit composition-dependent average crystallite sizes of <5.33 nm.The adopted approach allows the generation of relatively well-dispersed Ir-Ru alloy nanoparticles on the carbon support without severe agglomeration.The activity of IrRu_(2)/C for the hydrogen oxidation reaction is 1.10 times that of the stateof-the-art Pt/C catalyst.Cell reversal testing by simulation of fuel starvation reveals that the durability of IrRu_(2)/C(~7 h) significantly exceeds that of the conventional Pt/C catalyst(~10 min) and is the highest value reported so far.Thus,the developed Ir-Ru alloy catalyst can be used to fabricate practical RTAs and replace Pt catalysts in the anodes of polymer electrolyte membrane fuel cells.展开更多
文摘Carbon-coated lithium manganese silicate （Li2MnSiO4/C） nanoparticles were synthesized by polyol process. X-ray diffraction （XRD） patterns of the obtained materials exhibit a good fit with that of the Li2MnSiO4 phase. Field emission scanning electron microscopy （FESEM） images of the obtained samples show that the particle size is only tens of nanometers. The high resolution transmission electron microscopy （HRTEM） analysis shows that the Li2MnSiO4 nanoparticles are surrounded by a very thin film of amorphous carbon. The composite prepared through polyol process shows good performance as cathode materials in lithium cells at room temperature. The charge capacity of the Li2MnSiO4/C samples is 219 mAh/g （about 1.3 Li^＋ per unit formula extracted）, and the discharge capacity is 132 mAh/g （about 0.8 Li^＋ per unit formula inserted） in the first cycle in the voltage range of 1.5-4.8 V. A good capacity cycling maintenance of 81.8% after 10 cycles was obtained.
基金This work was supported by the National Natural Science Foundation of ChinaNatural Science Foundation of Qinghai Province.
文摘A new form of Cu2O, disk-like structure with 60 nm in thickness and 2 μm in diameter,has been successfully synthesized in bulk quantities by polyol process in the presence of PVP K-30.
文摘Polymer-protected monodisperse nickel nanoparticles were synthesized by a modified polyol reduction method in the presence of poly（N-vinyl-2-Pyrrolidone）.These nanoparticles were characterized by transmission electron microscopy（TEM）,X-ray diffraction（XRD）,selected area electron diffraction（SAED）,as well as vibrating sample magnetometer（VSM）.The experimental results show that the addition of PVP and the concentration of NaOh have strong influences on the size.agglomeration and uniformity of nanoparticles.In the presence of PVP and NaoH with low concentration.smonodisperse nickel nanoparticles with average diameters about 42 nm were obtained and characterized to the pure nickel crystalline with foc structure.Secondary structures such as clusters.loops.and strings resulted from magnetic interactions between particles were observed.The chemical interaction between the PVP and nickel nanoparticles was found by FTIR.The saturation magnetization（Ms）.remanent magnetization（Mr）and coercivity（Hc）of these nickel nanoparticles are lower than those of bulk nickel.
基金supported by the National Science Foundation for Distinguished Young Scholars of China(No.51025209)the National Nature Science Foundation of China(No.21103089)the Key Projects in Nature Science Foundation of Jiangsu Province(No.BK2011030)
文摘Amorphous carbon and graphene co-modified LiFePO4 nanocomposite has been synthesized via a facile polyol process in connection with a following thermal treatment.Various characterization techniques,including XRD.Mossbauer spectra,Raman spectra,SEM,TEM,BET,O2-TPO,galvano charge-discharge,CV and EIS were applied to investigate the phase composition,carbon content,morphological structure and electrochemical performance of the synthesized samples.The effect of introducing way of carbon sources on the properties and performance of LiFePO4/C/graphene composite was paid special attention.Under optimized synthetic conditions,highly crystalized olivine-type LiFePO4was successfully obtained with electron conductive Fe2P and FeP as the main impurity phases.SEM and TEM analyses demonstrated the graphene sheets were randomly distributed inside the sample to create an open structured LiFePO4 with respect to graphene,while the glucosederived carbon mainly coated over LiFeP04 particles which effectively connected the graphene sheets and LiFePO4 particles to result in a more efficient charge transfer process.As a result,favorable electrochemical performance was achieved.The performance of the amorphous carbon-graphene co-modified LiFePO4 was further progressively improved upon cycling in the first 200 cycles to reach a reversible specificcapacity as high as 97 mAh·g-1 at 10 C rate.
文摘Zinc oxide nanoparticles with different sizes and shapes have been synthesized in polyol using a bottom-up approach. We have studied the scale-up of the process to massively produce high quality nanoparticles of controlled size and shape. The scale-up strategy required the effective mixing of reagents using either axial or radial mixing configurations and was experimentally validated by comparing structural properties of particles obtained in a small and a large size reactor. In addition, the flow patterns in these reactors have been calculated using three-dimensional turbulent computational fluid dynamics (CFD) simulations. Our results indicate a strong connection between the flow patterns, as obtained by CFD simulations, and the size and shape of the particles. Actually, our pilot scale reactor allowed producing sample aliquots of ~50 grams with nanoparticle sizes ranging from 8 nm to 600 nm and aspect ratio varying from 1 (nanospheres) to 20 (nanorods). After their synthesis, these two nanoparticle classes have been tested as building blocks in D149-dye-sensitized solar cell (DSSC). The measured power conversion efficiency (PCE) was 4.66% for nanorods shaped particles and 4.21% for nanospheres. These values were significantly higher than the 3.90% PCE obtained with commercial Degussa VP20 ZnO nanoparticles.
基金financial supports from National Key R&D Plan of China (2017YFB0102803)the National Natural Science Foundation of China (21676135)+8 种基金Scientific Instrument Develop Major Project of National Natural Science Foundation of China (51627810)Joint Funds of the National Natural Science Foundation and Liaoning of China (U1508202)Key R&D programs in Jiangsu (BE2018051)“333” project of Jiangsu Province (BRA2018007)Natural Science Foundation of Jiangsu Province (BK20161273, BK20181199)the Graduate Innovation Foundation of Nanjing university (2017ZDL05)support of PAPD of Jiangsu Higher Education Institutions“Six Talent Peaks Program” of Jiangsu ProvinceFundamental Research Funds for the Central Universities, China。
文摘A series of Pt/C catalysts for proton exchange membrane fuel cells(PEMFCs) with various metal loadings is synthesized by a microwave-assisted polyol process via mixing an extremely stable platinum colloid(> 3 months’ shelf life) from single batch preparation with activated carbon ethylene glycol suspension.21 wt%, 42 wt% and 61 wt% Pt loadings are employed to showcase the advantages of the improved polyol process. The ultraviolet(UV)–visible spectra and ζ-potential measurements are conducted to monitor the wet chemistry process during catalyst preparation. The powder X-ray diffraction(XRD), transmission electron microscopy(TEM) and thermogravimetric analysis(TGA) characterizations are carried out on catalysts. The catalyst activities are investigated using electrochemical and single cell tests. The stability of Pt nanoparticle colloid is explored by ORR, cyclic voltammetry(CV) and ζ-potential measurements. The TEM results show the Pt particle sizes of the colloid, and the sizes of the 21 wt%, 42 wt% and 61 wt%Pt/C samples are 2.1–3.9 nm. Because of the high Pt dispersion, the Pt/C catalysts exhibit superior electroactivity toward ORR. In addition, four 61 wt% Pt/C catalysts made from the Pt colloid with 0–3 months’ shelf life show almost the same performance, which exhibits superior stability of the Pt colloid system without surfactant protection.
基金supported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP)the Ministry of Trade,Industry&Energy(MOTIE)of the Republic of Korea[Grant No.20183010032380]a GIST Research Institute(GRI)grant funded by the GIST in 2020。
文摘To address the problem of fuel starvation in fuel-cell electric vehicles,which causes cell voltage reversal and results in cell failure when repeated continuously,we developed a reversal-tolerant anode(RTA) to promote water oxidation in preference to carbon corrosion.Graphitized carbon-supported Ir-Ru alloys with different compositions are employed as RTA catalysts in an acidic polyol solution and are shown to exhibit composition-dependent average crystallite sizes of <5.33 nm.The adopted approach allows the generation of relatively well-dispersed Ir-Ru alloy nanoparticles on the carbon support without severe agglomeration.The activity of IrRu_(2)/C for the hydrogen oxidation reaction is 1.10 times that of the stateof-the-art Pt/C catalyst.Cell reversal testing by simulation of fuel starvation reveals that the durability of IrRu_(2)/C(~7 h) significantly exceeds that of the conventional Pt/C catalyst(~10 min) and is the highest value reported so far.Thus,the developed Ir-Ru alloy catalyst can be used to fabricate practical RTAs and replace Pt catalysts in the anodes of polymer electrolyte membrane fuel cells.
