Browsing by Author "Hung, Chung Jung"

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Electrophoretic Fabrication and Characterizations of Manganese Oxide/Carbon Nanotube Nanocomposite Pseudocapacitors
(2011)
Hung, Chung Jung
;
Hung, Jeng Han
;
Lin, Pang
;
Tseng, Tseung Yuen
;
材料科學與工程學系
This study reports the electrochemical performance and stability of MnO(x)-multiwall carbon nanotubes (MWCNTs) nanocomposite/Ni pseudocapacitor electrodes fabricated by a modified electrophoretic deposition (EPD) method. The nanocomposite electrode consisting of highly dispersed manganese oxide on MWCNTs was synthesized by a redox titration method at room temperature. The electrochemical properties of the electrode were demonstrated by cyclic voltammetry. The mean specific capacitances at a constant scan rate of 100 mV/s of MnO(x)-MWCNTs nanocomposites without and with heat treatment at temperatures 150, 200, and 250 degrees C for 2 h are 378, 402, 445, and 469 F/g, respectively, which indicate an increase with increasing annealing temperature. During stability tests, the as-grown MnO(x)-MWCNTs nanocomposite electrode can preserve 80% of its original capacitance after 6000 cycles of operation which can be increased to 86% after annealing at 200 degrees C for 2 h. The EPD MnO(x)/MWCNTs coaxial nanocomposite pseudocapacitors with manganese oxide ionized by H(+) ion process exhibit high specific capacitance, fast reaction rate, high stability, and have high potential for practical applications. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3601862] All rights reserved.
Electrophoretic fabrication and pseudocapacitive properties of graphene/manganese oxide/carbon nanotube nanocomposites
(2013-12-01)
Hung, Chung Jung
;
Lin, Pang
;
Tseng, Tseung Yuen
;
材料科學與工程學系
;
電子工程學系及電子研究所
Hybrid nanocomposites provided a synergistic improvement on electrochemical performance and stability for pseudocapacitor. Designed graphene/carbon nanotubes (CNTs)/MnO2 nanocomposites with CNTs electrode (in short, GMC + C) with highly nanoporous framework surface structure are fabricated by a modified electrophoretic deposition (EPD) method. Scanning electron microscopy and transmission electron microscopy analysis demonstrate that the flake-like MnO2 thickness (about less than 10 nm) and uniformly distributed on the porous graphene/CNTs framework. X-ray diffraction shows the formation of birnessite-type MnO2. Pseudocapacitances of the GMC + C electrode calculated by cyclic voltammetry having different scan rates of 5, 20, 50, 100, and 300 mV s(-1) exhibit high specific capacitances of 481, 436, 413, 398, and 372 F g, respectively. Sodium ion diffusion coefficients of the GMC + C electrode show a higher intercalation value of 3.647 x 10(-8) cm(2) s(-1) and deintercalation value of 2.899 x 10(-8) cm(2) s(-1) using chronoamperometry. Moreover, the GMC + C electrode maintains a high specific capacitance of 346 F g(-1), and is about 833% of the initial capacitance after 15,000 charge/discharge cycles. The designed hybrid GMC + C nanocomposites pseudocapacitor electrode using EPD route with the high specific capacitance, fast reaction rate, and high stability, exhibits high potential for practical applications. (C) 2013 Elsevier B.V. All rights reserved.
Fabrication of Flexible Electrochromic Devices Based on Tungsten Trioxide Nanobundles
(2016)
Chen, Chih Hao
;
Tseng, Tseung-Yuen
;
Hung, Chung Jung
;
材料科學與工程學系
;
電子工程學系及電子研究所
Low-cost and facile approach to grow quasi-one-dimensional hexagonal tungsten trioxide nanobundles(Q1D hex-W0(3) NBs) on indium tin oxide (ITO) coated flexible polyethylene terephthalate (PET) substrate via hydrothermal method combined with electrophoretic deposition (EPD) technique is reported. Influence of the precursor concentration and hydrothermal reaction time on the morphology and size of as synthesized W0(3) nanostructures are investigated. Well-designed nanostructure exhibits remarkable enhancement in the electrochromic (EC) properties. In particular, a significant optical modulation (44% at 700 nm), fast color switching speed (bleaching: 22 s and coloration: 9 s), high coloration efficiency (89.8 cm(2) C-1 at 700 nm), high Li+ diffusion coefficient (8.92 x 10(-10) cm(2) s(-1)), and excellent cycling stability (74% after 1000 cycles) are achieved for the QM hex-W0(3) Nils film. Improved EC properties are mainly attributed from the Q1D hex-W0(3) NBs. Li+ can transport quickly and easily diffused into the storage sites of the interface of the Nils. Furthermore, we also reported a large areal flexible EC device (70 mm x 70 mm) with a simple two electrode configuration exhibiting outstanding mechanical flexibility and high optical contrast. The QM hex-WO3 NBs film acts as an excellent EC material.
Graphene/Carbon Nanotube/MnO2 Nanocomposite Based Asymmetric Pseudocapacitors
(2014-01-01)
Hung, Chung Jung
;
Tseng, Tseung-Yuen
;
材料科學與工程學系
;
電子工程學系及電子研究所
;
Department of Materials Science and Engineering
Graphene/carbon nanotubes (CNTs)/manganese oxide (MnO2) nanocomposites plus CNTs (in short, GMC+C) and graphene/CNTs hybrid (in short, GC) thin-film electrodes are fabricated by electrophoretic deposition (EPD). Aqueous electrolyte-based asymmetric pseudocapacitors exhibiting a cell voltage of 1.8 V is successfully prepared using GMC+C nanocomposite as cathode and GC nanocomposite as anode. The asymmetric pseudocapacitor possesses superior performance with a maximum energy density of 204.12 Wh kg(-1). The asymmetric cell configuration exhibits excellent cycling stability with 91% of the specific capacitance maintained after 5,000 cycle tests. These results indicate that our designed asymmetric pseudocapacitors are appropriate for practical applications.
High energy density asymmetric pseudocapacitors fabricated by graphene/carbon nanotube/MnO2 plus carbon nanotubes nanocomposites electrode
(2014-08-01)
Hung, Chung Jung
;
Lin, Pang
;
Tseng, Tseung Yuen
;
材料科學與工程學系
;
電子工程學系及電子研究所
Novel graphene/carbon nanotubes (CNTs)/manganese oxide (MnO2) nanocomposites plus CNTs (GMC + C) and graphene/CNTs hybrid (GC) thin-film electrodes are prepared by electrophoretic deposition (EPD). These nanocomposite electrodes exhibit high surface area and interconnected pore networks. The GMC + C nanocomposite electrode shows excellent specific capacitance of 964 F g(-1) at 1 A g (-1), rate capability with the residual capacitance of 529 F g(-1), at 500 mV s(-1), and fast Na+ diffusion with intercalation value of 6.34 x 10(-7) cm(2) s(-1), and deintercalation value of 8.86 x 10(-7) cm(2) s(-1). Such excellent pseudocapacitive performances are attributed to low ion/electron transport resistances and short ion/electron diffusion lengths. Furthermore, novel aqueous electrolyte-based asymmetric pseudocapacitor having 1.8 V cell voltage is successfully fabricated using GMC + C nanocomposite as a cathode and GC nanocomposite as an anode. The optimized asymmetric pseudocapacitor possesses superior performance with a maximum energy density of record high 304 Wh kg(-1) and retaining 56.2% of its initial specific energy density at the power density up to 242 kW kg(-1). In addition, the asymmetric cell configuration also shows excellent cycling stability with 89% specific capacitance maintained after 10,000 cycles. These results suggest that our designed asymmetric pseudocapacitors have a high potential for practical applications. (C) 2014 Elsevier B.V. All rights reserved.
Hydrothermal Formation of Tungsten Trioxide Nanowire Networks on Seed-Free Substrates and Their Properties in Electrochromic Device
(2014-05-01)
Hung, Chung Jung
;
Huang, Yi Hsuan
;
Chen, Chih Hao
;
Lin, Pang
;
Tseng, Tseung Yuen
Facile and cost-efficient hydrothermally grown 3-D tungsten trioxide (WO3) nanowires (NWs) network film on seed-free fluorine-doped tin oxide (FTO) substrates without using additive or capping agent is reported. The NW networks are hexagonal phase and the morphologies are changed by adjusting the pH of precursor solutions. Growth mechanism of WO3 NWs is also extensively discussed. The designed porous film exhibits remarkable enhancement of the electrochromic (EC) properties. In particular, a significant optical modulation (57% at 632 nm), fast color switching speed (bleaching: 7 s and coloration: 21 s), high coloration efficiency (120.3 cm(2) C-1 at 632 nm), high Li+ diffusion coefficient (2.14 x 10(-9) cm(2) s(-1)), and excellent cycling stability (87% after 1000 cycles) are achieved for the 3-D NWs film. The improved EC properties are mainly attributed to the highly porous film, which makes the Li+ diffusion becomes easier and provides larger specific surface area for charge-transfer reactions. Furthermore, we also reported an EC device (50 mm x 50 mm) with a simple two-electrode configuration showing high optical contrast. The 3-D WO3 NWs network film acts as an excellent EC material.