86 research outputs found
SnO2 encapsulated TiO2 hollow nanofibers as anode material for lithium ion batteries
No full textNanoparticulate SnO2 was encapsulated into TiO2 hollow nanofibers to achieve high energy density and robust electrochemical performance as an anode material for lithium ion batteries. The SnO2 encapsulated TiO2 hollow nanofibers exhibit improved electrochemical performances over the TiO2 hollow nanofibers, including a high discharge capacity of similar to 517 mAh g(-1) and doubled capacity at a 10 C rate. These improvements on electrochemical performances are attributed to favorable mechanics and kinetics associated with lithium.This work was financially supported by the National Research Foundation of Korea through grant no. K20704000003TA050000310, the Global Research Laboratory Program provided by the Korean Ministry of Education, Science and Technology in 2011, the International Cooperation program of the Korea Insitute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government Ministry of Knowledge Economy (No. 2011T100100369) and the World Class University program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology (R31-10092)
Polyaniline/Polyoxometalate Hybrid Nanofibers as Cathode for Lithium Ion Batteries with Improved Lithium Storage Capacity
No full textPolyaniline is a member of the class of electrically conducting polymers, which have possible commercial applications as anticorrosive or static charge removal coatings. Aqueous-based polyaniline coatings are preferred over organic solvent or strong acid based coatings because the water used in these coatings does not pollute the environment. The overall goal of this dissertation was to further the development of useful water-based polyaniline coatings by studying new methods of synthesizing polyaniline particles for water-based coatings, to investigate the material properties of these particles such as molecular weight, electrical conductivity, particle size distribution, and stability of polyaniline in air and water. One method of polymerizing polyaniline for aqueous-based coatings uses micelles, which are composed of a cluster of amphiphile surfactants. Micelles can change the local environment by aligning and absorbing the monomer, and may yield polymers with improved material properties and reaction rates. Nonionic micelles have not been extensively investigated. Therefore the first specific goal of this work was to use an aqueous nonionic micelle solution of nonylphenoxypoly(ethyleneoxy) ethanol surfactant (NP-30 surfactant) to comprehensively investigate a one step chemical polymerization of polyaniline conducted at ?3°C, in 1.25 M HCl, with ammonium peroxydisulfate oxidizer. The results show that increasing surfactant concentrations caused a decrease in molecular weight, electrical conductivity and sharper particle size distribution of the polymer. The second specific objective of this dissertation was to determine the effect of water and air on polyaniline. The results showed no degradation of molecular weight, a decrease in chloride and hydrogen composition, and decrease in electrical conductivity for polyaniline immersed in water for extended periods. A chloride ion diffusion coefficient of 2.5 to 74 × 10<super>?9</super> cm<super>2</super>/hour was measured. The aging of polyaniline powders in a desiccator for 5 years showed no effect on the molecular structure as indicated by the FTIR spectrum. The third specific goal of the research was to measure the real and imaginary refractive index of polyaniline saturated with 1.25 M HCl, which was found to be 1.345 to 1.355 and 0.025 to 0.027, respectively. This information is crucial to measuring the distribution of polyaniline colloids by light scattering
Synergistic oxidation of NADH on bimetallic CoPt nanoparticles decorated carbon nitride nanotubes
No full textWe demonstrate that carbon nitride nanotube (CNNT) hybrids modified with CoPt nanoparticles (CoPt NPs) oxidize reduced nicotinamide adenine dinucleotide (NADH) to a greater extent than carbon nanotubes (CNTs) or CNNTs alone due to synergistic interactions between the CNNTs and the CoPt NPs through the improved internal network. Heterogeneous nitrogen atoms in the sp(2) carbon network provide strong binding sites for in-situ synthesis of CoPt NPs of homogeneous size. The increase in heterogeneous charge transfer on the CoPt-CNNT hybrid electrode enhanced the electrochemical oxidation of NADH at a low applied potential compared to those for pristine CNTs or CNNTs. Our results suggest that CoPt-CNNT hybrids are highly stable and ideal for use in electrochemical sensing. (C) 2014 Elsevier B.V. All rights reserved.This work was supported by the Global Research Laboratory (GRL) Program (K20704000003TA050000310) through the National Research Foundation (NRF) of Korea funded by the Ministry of Science, ICT and Future Planning (MSIP), an International Cooperation program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korean Ministry of Trade, Industry & Energy (2011T100100369), the Nano Material Technology Development Program (2012M3A7B4035286), the Basic Science Research Program (2012R1A6A1029029), Mid-career Researcher Program (2013R1A2A2A03015161) and the World Class University (WCU) Program (R31-10092) through the NRF funded by the MSIP. This research was also supported by the Korea Center for Artificial Photosynthesis (2009-0093881) and the Global Frontier R&D Program (2013M3A6B1078865) on Center for Hybrid Interface Materials (HIM) funded by the MSIP and the NRF of Korea (2011-0028737, 2012M1A2A2671813)
Dominant Factors Governing the Rate Capability of a TiO2Nanotube Anode for High Power Lithium Ion Batteries
No full textTitanium dioxide (TiO2) is one of the most promising anode materials for lithium ion batteries due to low cost and structural stability during Li insertion/extraction. However, its poor rate capability limits its practical use. Although various approaches have been explored to overcome this problem, previous reports have mainly focused on the enhancement of both the electronic conductivity and the kinetic associated with lithium in the composite film of active material/conducting agent/binder. Here, we systematically explore the effect of the contact resistance between a current collector and a composite film of active material/conducting agent/binder on the rate capability of a TiO2-based electrode. The vertically aligned TiO2 nanotubes arrays, directly grown on the current collector, with sealed cap and unsealed cap, and conventional randomly oriented TiO2 nanotubes electrodes were prepared for this study. The vertically aligned TiO2 nanotubes array electrode with unsealed cap showed superior performance with six times higher capacity at 10 C rate compared to conventional randomly oriented TiO2 nanotubes electrode with 10 wt % conducting agent. On the basis of the detailed experimental results and associated theoretical analysis, we demonstrate that the reduction of the contact resistance between electrode and current collector plays an important role in improving the electronic conductivity of the overall electrode system.This work was financially supported by the National Research Foundation of Korea (NRF) through Grant No. K20704000003TA050000310, Global Research Laboratory (GAL) Program provided by the Korean Ministry of Education, Science and Technology (MEST) in 2011, the International Cooperation program of the Korea Insitute of Energy Technology Evaluation and Planning(KETEP) grant funded by the Korea Ministry of Knowledge Economy (No. 2011T100100369), and WCU (World Class University) program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology (R31-10092)
Tin indium oxide/graphene nanosheet nanocomposite as an anode material for lithium ion batteries with enhanced lithium storage capacity and rate capability
No full textTin oxide (SnO2) is a promising candidate as an anode for lithium ion batteries because of its high theoretical capacity. However, poor capacity retention caused by large volume changes during cycling, large initial irreversible capacity, and low rate capability frustrate its practical application. We have developed a ternary nanocomposite based on tin indium oxide (SnO2-In2O3) and graphene nanosheet (GNS) synthesized via a facile solvothermal method. The incorporation of In2O3 into SnO2 can improve the electrochemical property of SnO2 and reduce the charge transfer resistance of electrode leading to the enhanced reversible capacity and rate capability. The graphene nanosheet in the composite electrode can accommodate high volume expansion/contraction during cycling resulting in excellent capacity retention. As an anode for lithium ion batteries, the SnO2-In2O3/GNS nanocomposite exhibits a remarkably improved electrochemical performance in terms of lithium storage capacity (962 mAh g(-1) at 60 mA g(-1) rate), initial coulombic efficiency (57.2%), cycling stability (60.8% capacity retention after 50 cycles), and rate capability (393.25 mAh g(-1) at 600 mA g(-1) rate after 25 cycles) compared to SnO2/GNS and pure SnO2-In2O3 electrode. (C) 2012 Elsevier Ltd. All rights reserved.This work Was financially supported by the National Research Foundation of Korea through grant no. K2070400000307A050000310, the Global Research Laboratory Program provided by the Korean Ministry of Education, Science and Technology in 2012, the International Cooperation program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government Ministry of Knowledge Economy (No. 2011T100100369) and the World Class University program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology (R31-10092)
Economics of the US - Canada Softwood Lumber Dispute: A Historical Perspective
No full textThis paper reviews the U.S.-Canada softwood lumber dispute over the past two decades by outlining the key developments and critically appraising the arguments put forward by both countries. It also presents a welfare analysis of lumber trade distortions. Given the importance of lumber trade between Canada and the United States, an expeditious resolution of this long-running trade dispute would be beneficial for both countries.antidumping and countervailing duties, lumber, trade distortions, welfare, Resource /Energy Economics and Policy,
Modulating the interaction between gold and TiO2 nanowires for enhanced solar driven photoelectrocatalytic hydrogen generation
No full textThe interaction strength of Au nanoparticles with pristine and nitrogen doped TiO2 nanowire surfaces was
analysed using density functional theory and their significance in enhancing the solar driven photoelectrocatalytic
properties was elucidated. In this article, we prepared 4-dimethylaminopyridine capped Au
nanoparticle decorated TiO2 nanowire systems. The density functional theory calculations show {101}
facets of TiO2 as the preferred phase for dimethylaminopyridine–Au nanoparticles anchoring with a binding
energy of 8.282 kcal mol1
. Besides, the interaction strength of Au nanoparticles was enhanced
nearly four-fold (35.559 kcal mol1
) at {101} facets via nitrogen doping, which indeed amplified the Au
nanoparticle density on nitrided TiO2. The Au coated nitrogen doped TiO2 (N–TiO2–Au) hybrid electrodes
show higher absorbance owing to the light scattering effect of Au nanoparticles. In addition, N–TiO2–Au
hybrid electrodes block the charge leakage from the electrode to the electrolyte and thus reduce the
charge recombination at the electrode/electrolyte interface. Despite the beneficial band narrowing effect
of nitrogen in TiO2 on the electrochemical and visible light activity in N–TiO2–Au hybrid electrodes, it
results in low photocurrent generation at higher Au NP loading (3.4 107 M) due to light blocking the
N–TiO2 surface. Strikingly, even with a ten-fold lower Au NP loading (0.34 107 M), the synergistic effects
of nitrogen doping and Au NPs on the N–TiO2–Au hybrid system yield high photocurrent compared to
TiO2 and TiO2–Au electrodes. As a result, the N–TiO2–Au electrode produces nearly 270 mmol h1 cm2
hydrogen, which is nearly two-fold higher than the pristine TiO2 counterpart. The implications of these
findings for the design of efficient hybrid photoelectrocatalytic electrodes are discussed.
IntroducGlobal Research Laboratory (GRL) Program through the National Research Foundation of Korea (NRF) - Ministry of Science. K20704000003TA050000310
Japan Society for the Promotion of Science (JSPS)
University Jaume I. P1.1B2014-51
Government of the Russian Federation. 074-U0
Synergistic Metal–Metal Oxide Nanoparticles Supported Electrocatalytic Graphene for Improved Photoelectrochemical Glucose Oxidation
No full textWe report the fabrication of graphene–WO3–Au hybrid membranes and evaluate their photocatalytic activity towards glucose oxidase mediated enzymatic glucose oxidation. The dual-functionality of gold nanoparticles in the reinforcement of visible light activity of graphene–WO3 membranes and improving the catalytic activity of immobilized enzymes for unique photoelectrochemical sensing application is demonstrated. This work provides new insights into the fabrication of light-sensitive hybrid materials and facilitates their application in future
Electrochemiluminescent Metallopolymer−Nanoparticle Composites: Nanoparticle Size Effects
No full textGold nanoparticle-composite nanofibers for enzymatic electrochemical sensing of hydrogen peroxide
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