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Hu G.,National University of Singapore | Li C.,Advanced Materials Technology Center | Gong H.,National University of Singapore
Journal of Power Sources

Nanoporous nickel hydroxide Ni(OH)2 coated on nickel foam by using a chemical bath deposition method shows a high specific capacitance of 2200 F g-1 at a discharging current density of 1 Ag-1. After 500 charge-discharge cycles, the specific capacitance is stabilized at 1470 Fg-1, and there is only a 5% fall in specific capacitance during the following 1500 cycles. The relationship between the capacitance decay and changes in the microstructure and morphology of nanoporous Ni(OH)2 is investigated. The results show that phase transformation and the growth of particle/crystal size, rather than the formerly proposed flaking off of Ni(OH)2, are the major factors contributing to the capacitance decay. © 2010. Source

Zhang D.W.,East China Normal University | Li X.D.,East China Normal University | Chen S.,East China Normal University | Tao F.,East China Normal University | And 3 more authors.
Journal of Solid State Electrochemistry

Double-walled carbon nanotubes (DWCNTs) have been studied for counter-electrode application in dye-sensitized solar cells (DSCs). Mesoporous TiO2 films are prepared from the commercial TiO2 nanopowders by screen-printing technique on optically transparent-conducting glasses. A metal-free organic dye (indoline dye D102) is used as a sensitizer. DWCNTs are applied to substitute for platinum as counter-electrode materials. Morphological and electrochemical properties of the formed counter electrodes are investigated by scanning electronic microscopy and electrochemical impedance spectroscopy, respectively. The electronic and ionic processes in platinum and DWCNT-based DSCs are analyzed and discussed. The catalytic activity and DSC performance of DWCNTs and Pt are compared. A conversion efficiency of 6.07% has been obtained for DWCNT counter-electrode DSCs. This efficiency is comparable to that of platinum counter-electrode-based devices. © Springer-Verlag 2009. Source

Hu G.,National University of Singapore | Tang C.,National University of Singapore | Li C.,Advanced Materials Technology Center | Li H.,National University of Singapore | And 2 more authors.
Journal of the Electrochemical Society

Nickel cobalt (Ni-Co) oxides with various Ni/Co ratios are synthesized by using a sol-gel process. Electrochemical performance, microstructure, morphology and BET surface area are found strongly related to Ni and Co concentration. Increasing Co concentration changes the oxide microstructure from NiO crystal dominate structure (Ni:Co 1:1 and 1:2) to Co3O4 dominate structure (Ni:Co 1:4 and 0:1). A maximum specific capacitance of 1539 Fg -1 was obtained for Ni-Co (Ni:Co 1:2) oxide at a current density of 1Ag-1, and this capacitance is similar to that of RuO2. A systematic study shows that the Ni-Co oxide (1:2) has a mesoporous structure with a high BET surface area of ∼ 315 m2 g-1 and porous size of ∼ 4.7 nm, which is favorable for the charge/dischargeprocess of a supercapacitor. © 2011 The Electrochemical Society. Source

Nguyen V.N.,Vietnam National University, Hanoi | Nguyen T.D.C.,Quy Nhon University | Dao T.P.,Vietnam National University, Hanoi | Tran H.T.,Advanced Materials Technology Center | And 2 more authors.
Journal of Industrial and Engineering Chemistry

Organoclays were synthesized by exchanging inorganic cations between layers in Thanh Hoa bentonite using organic cations including benzylhexadecyldimethylammonium (BHDDM+), dimethyldioctadecylammonium (DMDOD+) and benzylstearyldimethylammonium (BSDM+). Inserting organic cations increases material interlayer distance significantly (from 15Å to 40Å) and simultaneously enhances affinity of materials toward organic pollutants. The results show that adsorption capacity of organics on organoclays strongly depends on affinity between organic substances and ammonium cations rather than on interlayer distance of organoclays. This means that the sorption of organoclays for organic contaminants was significantly influenced by the nature of the surfactants added to the clay. © 2012 The Korean Society of Industrial and Engineering Chemistry. Source

Liu L.,National University of Singapore | Yang Z.H.,National University of Singapore | Kong L.B.,National University of Singapore | Li P.,Advanced Materials Technology Center
IEEE Transactions on Electromagnetic Compatibility

Novel flexible transparent composite sheets were fabricated with glass-coated nanocrystalline ferromagnetic microwires and transparent silicone matrix. The free-space method was employed to measure the effective permittivity and shielding effectiveness (SE) of samples fabricated from 4 to 20 GHz. SE of the transparent shielding layer with 1wt of microwires and thickness of 0.85 mm can be more than 20 dB when frequency is above 11 GHz. Due to resonance phenomena of the embedded shortcut microwires with a length of about 5 mm, both dielectric permittivity and loss of the composite are quite high at microwave frequency. Hence, such transparent composite sheets may also find applications in microwave applications © 2006 IEEE. Source

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