Browsing by Author "Chen, Ting-Ting"

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Alkali metal ion assisted synthesis of faceted anatase TiO2
(2013)
Yang, Min-Han
;
Chen, Po-Chin
;
Tsai, Min-Chiao
;
Chen, Ting-Ting
;
Chang, I-Chun
This work reports on a simple hydrothermal method for tuning the shape and exposed face of TiO2 nanocrystal by using sodium titanate as a precursor in the presence of different alkali metal ion salts. The {101}-exposed anatase TiO2 was synthesized in lithium salt solution. The formation of anatase TiO2 with exposed high-index {301} facet, obtained in the presence of sodium ions, has never before been reported upon. When the reaction proceeded in potassium salt solution, the obtained anatase TiO2 with a high aspect ratio was elongated in the < 001 > direction. Anatase TiO2 with a high aspect ratio was obtained in hydrothermal process in the presence of low charge density high atomic number alkali metal ions, which were not easily absorbed by the {001} planes of anatase, so the growth along this direction was not restrained. The photodegradation of methylene blue, assisted by anatase TiO2 with various exposed faces reveals that the photoactivity of anatase {101} planes is larger than that of {301} planes.
Anatase and brookite TiO2 with various morphologies and their proposed building block
(2014)
Yang, Min-Han
;
Chen, Po-Chin
;
Tsai, Min-Chiao
;
Chen, Ting-Ting
;
Chang, I-Chun
In this work, brookite TiO2 has been synthesized by a simple hydrothermal approach using sodium titanate as a precursor in the presence of a sodium fluoride aqueous solution. The ratio of brookite and anatase TiO2 can be tailored by the NaF concentration. In a concentrated NaF solution, high quality brookite TiO2 was acquired. Pure anatase nanoparticles were obtained in only deionized water. Moreover, the morphology and size of brookite TiO2 can be tailored by using various acid treated titanates which influence the stability of the building blocks and nucleation points of TiO2. Micro-sized flower-like brookite, submicro-sized urchin-like brookite and brookite nanorods with anatase nanoparticles were obtained. The micro-sized flower-like brookite remains the same shape and phase even at 800 degrees C, whereas obvious grains were formed on the matrix with brookite, rutile and anatase mixture phases at 900 degrees C. On the other hand, as the submicro-sized urchin-like brookite was heated, a rutile phase appeared at 750 degrees C and 100% grain-like rutile was obtained at 900 degrees C.
Electrochromism of rutile nanowires, vertically aligned along the [001] direction, due to alkali metal ion intercalation
(2011)
Yang, Min-Han
;
Chen, Ting-Ting
;
Wang, Yu-Shiuan
;
Chiu, Hsin-Tien
;
Lee, Chi-Young
Rutile nanowires were grown along the [001] direction and perpendicular to the fluorine doped tin oxide coated glass substrate (R(perpendicular to)) by a solvothermal process using titanium isopropoxide as the precursor in acidic solution. The edge length of the nanowires obtained in isopropyl alcohol is ten times less than that of the nanowires obtained in water. Due to the high ionic diffusion rate along the rutile [001] direction and good optical transmittance, R(perpendicular to) was used as an electrochromism electrode. When -2 V was applied, the color of the electrode became blue with a 60% change in the transmittance for 30 s due to the cathodic polarization potential in LiClO(4)/PC electrolyte (where PC is propylene carbonate). The lithium ion intercalated/extracted densities of R(perpendicular to), P25-coated and rutile nanowires-coated electrodes are 138.6/129.1 mC cm(-2), 93.6/83.2 mC cm(-2) and 31.7/15.9 mC cm(-2) respectively. After 50 cycles, the R(perpendicular to) electrode still performs very well. Furthermore, a large amount of sodium cation intercalation into TiO(2) was observed for the first time at -1.0 V. According to these results, the R(perpendicular to) electrode is a promising candidate to be a multi-function device.
Large-scale synthesis of uniform Cu2O nanocubes with tunable sizes by in-situ nucleation
(2013)
Chang, I-Chun
;
Chen, Po-Chin
;
Tsai, Min-Chiao
;
Chen, Ting-Ting
;
Yang, Min-Han
Uniform Cu2O nanocubes with various sizes were synthesized by reducing Cu(OH)(2) using ascorbic acid in the presence of various amounts of sodium citrate. The monodispersed nanocubes with an edge length of approximately 80 nm used as an anode exhibit excellent lithium storage behavior.
Porous titanium oxynitride sheets as electrochemical electrodes for energy storage
(2014)
Chen, Ting-Ting
;
Liu, Hsiao-Ping
;
Wei, Yen-Ju
;
Chang, I-Chun
;
Yang, Min-Han
A flexible, porous TiOxNy sheet consisting of numerous conductive fibers was synthesized by nitridation of titanate and further used as an electrochemical electrode. The high surface area and mixed-oxidation state of titanium make TiOxNy sheets to be promising candidates for a good supercapacitor.
Self-powered electrochemical deposition of Cu@Ni(OH)(2) nanobelts for high performance pseudocapacitors
(2014)
Chang, I-Chun
;
Chen, Ting-Ting
;
Yang, Min-Han
;
Chiu, Hsin-Tien
;
Lee, Chi-Young
Two aluminum-driven spontaneous electrochemical reactions are developed for depositing Cu@Ni(OH)(2) nanobelts on carbon/aluminum electrodes. The Cu@Ni(OH)(2) NBs function as pseudocapacitor electrodes, which exhibit a high specific capacitance of 2426 F g(-1) and a remarkable rate performance.
Size-controlled wurtzite zinc oxide spheres with the characteristics of visible absorption and Mie scattering
(2014)
Chen, Ting-Ting
;
Chang, I-Chun
;
Tsai, Min-Chiao
;
Chang, Yi-Chun
;
Yang, Min-Han
The enhancement of the light harvesting efficiency over a metal oxide is crucial to optic-related applications which can convert solar energy into chemical energy. Here, we demonstrated a method to develop the characteristics of visible light absorption and visible Mie scattering over wurtzite ZnO microspheres. Size-controlled ZnO microspheres were successfully prepared in the thermal decomposition of amorphous/ layered basic zinc salt (LBZ) spheres. Firstly, trisodium citrate was employed as the chelating agent to synthesize amorphous/LBZ microspheres in a nucleation-controlled method. The sphere size was controlled by the nuclei number, which depends on the competition between hydroxyl ions and citrate to the ligand with Zn2+. Secondly, visible-active wurtzite ZnO spheres were obtained by thermal decomposition. The uniform sized microspheres exhibited Mie scattering in the visible range due to the interaction with specific incident electromagnetic radiation, and the full absorption spectrum was easily obtained by tuning the size of the spheres. Such uniform spheres exhibited superior visible absorption and scattering effects and thus are expected to be good candidates for the optic-related applications.
SrTiO3/TiO2 Hybridstructure as Photoanode in Dye-Sensitized Solar Cell
(2013-12-01)
Wang, Yu-Shiuan
;
Chen, Ting-Ting
;
Huang, Yi-Jen
;
Huang, Tzu-Ping
;
Lee, Yin-Yu
In dye-sensitized solar cells (DSSCs), the charge recombination at the TiO2/dye/electrolyte interface greatly influences the photoelectron conversion efficiency. Hybrid semiconductor materials with matched band potentials are designed to reduce the charge recombination. In this study, SrTiO3/TiO2 hybridstructure was synthesized by using TiO2 nanoparticles as template in a hydrothermal, showing a negative shift in the flat band potential. The DSSC with the SrTiO3/TiO2 anode exhibits an increased photovoltage and a reduced photocurrent. The suppression of charge recombination at the TiO2/dye/electrolyte interface was observed in the electrochemical impedance spectroscopy, causing an improvement in the photovoltage. However, the SrTiO3/TiO2 system shows an obstructed electrons injection from the dye to SrTiO3/TiO2, limiting the photocurrent performance. The photoelectrochemical properties of the SrTiO3/TiO2 system are discussed in detail herein.
The "cascade effect" of nano/micro hierarchical structure: A new concept for designing the high photoactivity materials - An example for TiO2
(2013-10-01)
Chen, Po-Chin
;
Tsai, Min-Chiao
;
Yang, Min-Han
;
Chen, Ting-Ting
;
Chen, Huang-Chin
The chrysanthemum-like TiO2 (CT800) was synthesized. It exhibited excellent photoactivity, which greatly exceeded that of conventional P25. To discover the key factors that governed the photocatalytic properties, the specific reduction of Ag+ ions was carried out and EPR spectra of CT800 were obtained. Both an HADDF image and EDX mapping indicated that the Ag+ ions tended to be reduced close to the center of the micro matrix of CT800. Moreover, the EPR spectra strongly suggest that the excited electrons tended to migrate toward the center of the micro matrix, resulting from a multiple junction, cascade effect, which efficiently reduces the recombination of excited electrons and holes and greatly increases the photoactivity. Additionally, the special morphology of CT800 was responsible for the hot spots at the surface of nano sheets and then contributing to its outstanding photocatalytic activity. Furthermore, the unidirectional electron transfer, because of the cascade effect, by materials of different sizes provides a new avenue for the design of electronic and photoelectrochemical devices. (c) 2013 Elsevier B.V. All rights reserved.
The exceptional photo-catalytic activity of ZnO/RGO composite via metal and oxygen vacancies
(2013-10-01)
Chen, Ting-Ting
;
Chang, I-Chun
;
Yang, Min-Han
;
Chiu, Hsin-Tien
;
Lee, Chi-Young
ZnO/reduced graphene oxide (RGO) nanocomposite with many zinc and oxygen vacancies, synthesized in a simple solvothermal reaction exhibits significant photocatalytic activity. Photoluminescence and electron paramagnetic resonance measurements indicate that the zinc vacancies and oxygen vacancies were generated on the ZnO surface, and were crucial to that photocatalytic behavior. The photodegradation of methylene orange was significantly reduced by the addition of h(+) and (OH)-O-center dot scavengers. Both zinc and oxygen vacancies cause effective charge separation in the photodegradation of methylene orange, which markedly inhibits the recombination of charges. The advanced photocatalytic behavior of the ZnO/RGO composite is discussed in detail herein. (c) 2013 Elsevier B.V. All rights reserved.