Browsing by Author "Chang, Sue-min"

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A salt-assisted approach for the pore-size-tailoring of the ionic-liquid-templated TiO2 photocatalysts exhibiting high activity
(2013-03-27)
Chang, Sue-min
;
Lee, Chung-yu
;
環境工程研究所
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Institute of Environmental Engineering
In this study, we develop a novel salt-assisted approach to adjusting the pore size of ionic-liquid-templated TiO2 photocatalysts by simply changing the concentrations and types of the inorganic salts. Four types of salts, including NaCl, CaCl2, NH4Cl, and NH4NO3, are selected in order to investigate the effects of the ionic radii and the charges of the constituent ions on the resulting textures. In addition, a mechanism that the salts assist the self-assembly of hydrophilic 1-butyl-3-methylimidazolium chloride (C(4)mimCl) molecules in hydrophobic benzyl alcohol is proposed. The templated TiO2 powder, which incorporates phosphate species to enhance its structural stability, exhibits a small pore size of 4.2 nm and a high surface area of 164 m(2) g(-1). Small amounts of the salts increase the ionic strength, slightly shrinking the template and the pore size, and pore expansion results when the salt/Ti ratio is above 0.2. The salts at a salt/Ti ratio of 1.0 remarkably extend the pore size to 8.7-16.8 nm in the order of NH4NO3 (16.8 nm)>NH4Cl (13.7 nm)>CaCl2 (12.4 nm)>NaCl (8.7 nm). Moreover, high surface areas of 154-199 m(2) g(-1) are still achieved. The ions that have large radii and high valence numbers are more capable of expanding the pores because of strong volume exclusion and Coulomb repulsion. The critical pore size for the adsorption of hydrated bisphenol A molecules within the pores is ca. 4.2 nm. Pore expansion facilitates mass diffusion in the channels and turns internal surface areas available for reactions, thus greatly enhancing the activity of the mesoporous photocatalyst by 2.7-5.5 times. (C) 2012 Elsevier B.V. All rights reserved.
ANYL 456-Fabrication of novel molecularly imprinted alumina-silica using non-hydrolytic sol-gel method for trace phosphine detection
(2007-08-19)
Chang, Sue-min
;
Hou, Ching-jung
;
Yen, Shao-Yi
;
Li, Shou-Nan
;
環境工程研究所
Characterization of Zr-doped TiO2 nanocrystals prepared by a nonhydrolytic sol-gel method at high temperatures
(2006-10-26)
Chang, Sue-min
;
Doong, Ruey-an
;
環境工程研究所
;
Institute of Environmental Engineering
Highly crystalline and surface-modified Zr-doped TiO2 nanorods were successfully prepared using a nonhydrolytic sol-gel method that involves the condensation of metal halides with alkoxides in anhydrous trioctylphosphine oxide (TOPO) at either 320 or 400 degrees C. In addition, the interaction of the cross-condensation between the Ti and Zr species was studied by characterizing the morphologies, crystalline structures, chemical compositions, surface properties, and band gaps of the nanocrystals obtained at different reaction temperatures and Zr-to-Ti stoichiometric ratios. Increases in the concentration of Zr4+ and in the reaction temperature led to large nanorods and regular shapes, respectively. In addition, only the anatase form was observed in the Zr-doped TiO2 nanorods. The Zr-to-Ti ratios obtained ranged from 0.01 to 2.05, all of which were far below the stoichiometric ratios used during the preparation of the samples (0.25-4). Moreover, the Zr4+ units accumulated mainly at the surface of the TiO2 nanocrystals. The band gaps of the Zr-doped TiO2 nanorods ranged from 2.8 to 3.8 eV, which are smaller than those of pure TiO2 (3.7 eV) or ZrO2 (5.2 eV). The Zr-doped anatase TiO2 nanorods prepared at 400 degrees C at an initial stoichiometric Zr-to-Ti ratio of 2: 3 exhibited the highest photoactivities for the decomposition of rhodamine B because of the presence of trace amounts of Zr4+ (Zr/Ti = 0.03) in the TiO2 and the regular shapes of these particles. DSC analysis indicated that the temperatures for forming nanocrystalline TiO2 and ZrO2 were 207 and 340 degrees C, respectively. Moreover, the reactivities of condensation between the Ti species were reduced when Zr species were involved in the NHSG reactions. The results obtained in this study clearly demonstrate that the faster kinetics for the generation of TiO2 controls the material properties as well as the photoactivities of the nonhydrolytic sol-gel-derived nanocrystals.
COLL 483-Fabrication of phosphated TiO2 through calcination of TOPO-capped nanocrystals
(2007-08-19)
Chang, Sue-min
;
Hou, Chieh-yao
;
環境工程研究所
;
Institute of Environmental Engineering
Contributions of Abundant Hydroxyl Groups to Extraordinarily High Photocatalytic Activity of Amorphous Titania for CO2 Reduction
(2020-05-21)
Kharade, Aparna K.
;
Chang, Sue-min
;
環境工程研究所
;
Institute of Environmental Engineering
Despite severe charge recombination occurring within the bulk lattice, sol-gel-derived amorphous TiO2 particles with abundant OH groups (81.6 mg/g) and high surface area (274 m(2)/g) were for the first time demonstrated to exhibit respectively 8-14 and 9 times higher photocatalytic activity for CO2 reduction than their thermally derived anatase crystals and the commercial P25 powder. Moreover, the high density of the OH groups (12.45/nm(2)) enabled the amorphous oxide to exhibit higher specific surface reactivity than the crystals. The OH groups not only converted CO2 molecules into bonded bicarbonate/carbonate species to improve CO2 chemisorption but also trapped holes to form Ti-O-O-Ti species when the OH density was higher than a threshold value of 8.74/nm(2), which synergistically promoted interfacial charge transfer. Bidentate carbonate and center dot CO2- were two active species that were able to underwent CO32- -> Ti-OOCH2 -> Ti-O-CH3 -> CH4 and center dot CO2- -> CO22- -> Ti-COOH -> CO sequences on the hydroxylated surface to produce CH4 and CO products, respectively. High coverage of the chemisorbed carbonate species selected for CO2 reduction rather than H-2 evolution to proceed. Moreover, it led with CH4 as the major product. Oxygen vacancies were the major active sites on the anatase crystals. Their influences on the surface transformations were also characterized to comprehensively understand the surface-controlled activity and selectivity.
Effects of mono-dentate and bi-dentate ligands on adsorption characteristics of Cu-ion-imprinted hybrids
(2019-12-01)
Chou, Chia-yin
;
Chang, Sue-min
;
Huang, Wan-Ting
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環境工程研究所
;
Institute of Environmental Engineering
Two types of functional monomers, 3-(2-aminoethylamino)-propyl-trimethoxysilane (AAPTS) and 3-aminopropyl-triethoxysilane (APTES), with similar amino groups but different denticity (AAPTS: bi-dentate; APTES: mono-dentate) were used to prepare Cu-ion-imprinted hybrids (IIHs), and their influences on the imprinting quality, adsorption ability, and selectivity of the IIHs were symmetrically investigated. The AAPTS-IIHs exhibited the highest imprinting factor (IF) of 17.7 at the Cu/AAPTS = 1/1 and the highest Cu selectivity (k > 6.5) at the Cu/AAPTS = 0.5-1/1, whereas the two corresponding performances (IF = 22.6, k > 1.7) in the APTES-IIHs occurred at the Cu/APTES molar ratio of 0.124/1 and 0.5/1, respectively. Stronger complexation ability of the bidentate ligand led the AAPTS-IIH to exhibit 6.3-6.9 times higher Cu affinity than the APTES-IIH powder. In addition, it resulted in a higher degree of homogeneity among the binding sites and created more selective environment within the imprinted cavities than the mono-dentate APTES monomer did. Square-planar 4-coordinate and linear 2-coordinate Cu complexes were the major forms imprinted in the AAPTS-based and the APTES-based systems, respectively. The exclusion ability of the AAPTS-IIH for the reference ions was in the order of Pb2+similar to Zn2+ > Ni2+ > Hg2+, while it was Zn2+> Pb2+> Ni2+> Hg2+ in the APTES-IIH powder. The imprinted hybrids select ions mainly based on the coordinate geometries of the ion-complexes, and the complexation stability was the second priority.
Effects of surface doped metal ions on the photocatalytic activity of titanium dioxide
(2012-08-19)
Liu, Wei S.
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Chang, Sue-min
;
環境工程研究所
;
Institute of Environmental Engineering
Enhanced photoactivity of Cu-deposited titanate nanotubes for removal of bisphenol A
(2013-01-17)
Doong, Ruey-an
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Chang, Sue-min
;
Tsai, Chia-wei
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環境工程研究所
;
Institute of Environmental Engineering
One-dimensional nanotubes are promising nanostructured materials for a wide variety of environmental applications. In this study, the Cu-deposited titanate nanotubes (TNTs) were fabricated using an alkaline hydrothermal method at 150 degrees C and then 0.5-2 wt% Cu(II) ions were photodeposited onto the calcined TNTs at 500 degrees C for enhanced photodegradation of bisphenol A (BPA) under illumination of 365 nm UV light. The as-synthesized TNTs showed tubular structures with the outer diameter and inter-layer spacing of 7-10 and 0.8 nm, respectively. The X-ray absorption near-edge spectral results provided a strong support on the partially structural change from layered trititanate to anatase TiO2 through the distortion of octahedral TiO6 unit at 500 degrees C and the production of mixture of CuO and Cu2O after photodeposition of Cu ions, resulting in the formation of Cu-deposited TiO2/TNT nanocomposites to enhance the photocatalytic activity. A nearly complete removal of BPA by the Cu-deposited TiO2/TNTs was observed, and the pseudo-first-order rate constants (k(obs)) for BPA photodegradation by Cu-deposited TiO2/TNTs at pH 7.0 were 1.8-5.2 and 4.3-12.7 times higher than those of pure Degussa P25 and ST01 TiO2, respectively. In addition, the k(obs) for BPA photodegradation reached the maximum value of 0.253 +/- 0.032 min(-1) at 1 wt% Cu(II). The X-ray photoelectron spectra showed that the ratio of Cu2O to total Cu increased from 3.2% in the dark to 35.2% after illumination of 365 nm UV light for 5 min. In addition, electron paramagnetic resonance results indicated that the copper ions could serve as the electron mediators to prolong the retention time of photo-generated radicals, resulting in the enhancement of photodegradation efficiency and rate of BPA by Cu-deposited TiO2/TNTs. (C) 2012 Elsevier B.V. All rights reserved.
ENVR 173-Photoactivity of TOPO-capped TiO2 nanocrystals toward the degradation of endocrine disrupting chemicals
(2007-08-19)
Chang, Sue-min
;
Lo, Pin-han
;
Hou, Chieh-Yao
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環境工程研究所
;
Institute of Environmental Engineering
Formation of Cu2O/Titanate/Titania Heterojunctions from Hydrothermally Induced Dual Phase Transitions
(2016-09-29)
Chaudhary, Manchal
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Chang, Sue-min
;
Doong, Ruey-an
;
Tsai, Hsin-mu
;
環境工程研究所
A microwave-assisted hydrothermal method has been developed as an efficient approach to readily induce phase transition of titanate assemblies in conjunction with decoration of Cu2O dusters on the surface. The influence of Cu2+ ions on the hydrothermally induced structural evolution was examined, and the roles of heterojunctions in the resulting composites in charge separation for improved photocatalytic activity were clarified. Hierarchical titanate assemblies with high adsorption capacity for Cu2+-ions (95.7 meg) were prepared from a low alkaline condition, Microwave-assisted hydrothermal treatment was then used to transform the adsorbents into Cu2O/titanate/titania photocatalysts in 20 min via inducing titanate-to-titania and Cu2+-to-Cu2O dual transitions. While tubular architecture was maintained in, the composites, the Cu2O dusters highly dispersed on the surface. Adsorbed Cu2+ ions have been found to retard the titanate-to-titania transformation locally, thus leading to Cu2O/titanate/titania heterojanctions. The multiheterojunctions enabled the composites to exhibit 1.7-5.1 times higher activity than the commercial product P25 (k(obs), 0.06 min(-1)) for decomposition of bisphenol A due to charge separation. EPR results dearly reveal that the type II band alignment effectively drove electrons and holes to migrate toward the titania and the Cu2O moieties, respectively, and the titanate moiety positioning in between prevented back recombination. The optimal C(u)2O loading to the highest activity (k(obs),0.306 min(-1)) Was -3.7 wt %. Over the optimal amount, the rower reduction potential in the valence band of the Cu2O dusters compensated for the positive effect from charge separation, thus causing the activity to decline in turn.
INOR 423-Fabrication of organic modified mesoporous TiO2 with high photocatalytic activity
(2008-08-17)
Chang, Sue-min
;
Shih, Chia-hsuan
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環境工程研究所
;
Institute of Environmental Engineering
INOR 65-Effect of surface and lattice vanadium ions on the physicochemical and photocatalytic properties of porous TiO2
(2007-08-19)
Chang, Sue-min
;
Liu, Wei-Szu
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Sung, Pin-Hsin
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環境工程研究所
;
Institute of Environmental Engineering
INOR 685-Preparation of surface salicylic acid modified titanium dioxide photocatalyst using microwave assisted method
(2008-08-17)
Chang, Sue-min
;
Chen, Tzu-yin
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環境工程研究所
;
Institute of Environmental Engineering
INOR 736-Calcination effect on the physicochemical properties of TOPO-capped ZrxTi1-xO2 nanocrystals
(2006-09-10)
Chang, Sue-min
;
Hou, Chieh-yao
;
Sung, Ping-shing
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環境工程研究所
;
Institute of Environmental Engineering
Interband transitions in sol-gel-derived ZrO2 films under different calcination conditions
(2007-09-18)
Chang, Sue-min
;
Doong, Ruey-an
;
環境工程研究所
;
Institute of Environmental Engineering
Different types of interband transitions as well as the microstructures and O/Zr ratios in sol-gel-derived ZrO2 films calcined at elevated temperatures in air or N-2 were systematically examined to clarify the formation of different band structures in the structural ZrO2 films. Optical absorptions indicate that the structural ZrO2 films all contain direct-band transitions, while the occurrence of indirect-band and band-tail transitions, depends on O/Zr ratios. Band tails mainly result from imperfect structures in the grain boundaries and appear in the ZrO2 films with O/Zr >= 2. When the ZrO2 films are non-stoichiometric (O/Zr < 2), indirect-band transitions occur due to the folded bands caused by lattice oxygen vacancies. Monoclinic ZrO2 has two direct-band transitions with bandgaps of 5.02-5.08 and 5.83-6.01 eV. The valence-band XPS spectra indicate that an additional occupied sub-band is located above its valence band. Indirect bandgaps in the monoclinic ZrO2 films are in the range of 5.00-5.10 eV. Amorphous ZrO2 films exhibit indirect-band transitions with bandgaps of 5.01-5.47 eV followed by direct-band transitions with bandgaps of 5.90-6.12 eV. In addition, tetragonal ZrO2 contains direct bandgaps of 5.32-5.74 eV and indirect bandgaps of 4.72-5.40 eV. Size-dependent bandgaps are observed in the sol-gel-derived ZrO2 films calcined in air, while the exponential dependence of bandgaps on O/Zr ratios is obtained in the ZrO2 films calcined in N-2. The discrepancy is primarily due to different fates of oxygen vacancies resulting from different calcination atmospheres.
Is Surface Doping or Bulk Doping More Beneficial to the Photocatalytic Activity of TiO2
(2014-01-01)
Chang, Sue-min
;
環境工程研究所
;
Institute of Environmental Engineering
Doping has been demonstrated to inhibit charge recombination and improve photocatalytic activity of photocatalysts. Conventional doping incorporates hetero-ions into the bulk lattice. In the presence of the defects, few charge carriers are trapped to suppress band-to-band recombination. Because most of trapped carriers annihilate with the counterparts, a low doping level is required, and the optimal doping concentration decreases with increasing particle size. Surface doping, on the other hand, only introduces dopants into the surface lattice. Surface-doped ions create an internal electric field to drive charge carriers to quickly drift to the surface. In addition, they trap the carriers and mediate charge transfer to the chemisorbed species. Compared to bulk doping, surface doping not only inhibits both bulk and surface recombination but also improves interfacial charge transfer, thus is more effective to improve photocatalytic activity.
Is surface doping or bulk doping more beneficial to the photocatalytic activity of TiO2?
(2013-09-08)
Chang, Sue-min
;
Liu, Wei-szu
;
環境工程研究所
;
Institute of Environmental Engineering
Mechanism of Photocatalytic CO2 Reduction by Bismuth-Based Perovskite Nanocrystals at the Gas-Solid Interface
(2019-12-25)
Bhosale, Sumit S.
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Kharade, Aparna K.
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Jokar, Efat
;
Fathi, Amir
;
Chang, Sue-min
We report here a series of nontoxic and stable bismuth-based perovskite nanocrystals (PeNCs) with applications for photocatalytic reduction of carbon dioxide to methane and carbon monoxide. Three bismuth-based PeNCs of general chemical formulas A(3)Bi(2)I(9), in which cation A(+) = Rb+ or Cs+ or CH3NH3+ (MK), were synthesized with a novel ultrasonication top-down method. PeNC of Cs3Bi2I9 had the best photocatalytic activity for the reduction of CO2 at the gas solid interface with formation yields 14.9 mu mol g(-1) of methane and 77.6 mu mol g(-1) of CO, representing a much more effective catalyst than TiO2 (P25) under the same experimental conditions. The products of the photocatalytic reactions were analyzed using a gas chromatograph coupled with a mass spectrometer. According to electron paramagnetic resonance and diffuse-reflectance infrared spectra, we propose a reaction mechanism for photoreduction of CO2 via Bi-based PeNC photocatalysts to form CO, CH4, and other possible side products.
Molecularly imprinted ZrO2 photonic-crystal sensors exhibiting high sensitivity and quick response
(2012-03-25)
Chang, Sue-min
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Fang, Chih-hsiang
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環境工程研究所
;
Institute of Environmental Engineering
Photocatalytic behavior of TOPO-capped TiO(2) nanocrystals for degradation of endocrine disrupting chemicals
(2009-09-28)
Chang, Sue-min
;
Lo, Pin-han
;
Chang, Chen-tuan
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環境工程研究所
;
Institute of Environmental Engineering
In this study, we investigated the photocatalytic kinetics and mechanisms of trioctylphosphine oxide-capped titanium dioxide (TOPO-capped TiO(2)) for degradation of two endocrine disrupting chemicals (EDCs), phenol and bisphenol A, which contained different hydrophobicity, chemiadsorbability, and degradable capacity. The TOPO-capped TiO(2) exhibited high partition coefficients of 2.00 x 10(-4) and 3.42 x 10(-3) l/mg for phenol and bisphenol A, respectively. In addition, the bonded TOPO introduced substantial amounts of trapped holes at the surface. The high affinity toward the target compounds and stabilized charge carriers resulted in high photocatalytic activity of the modified TiO(2). The TOPO-capped TiO(2) exhibited 12- and 3-fold higher photocatalytic activities than P25 for decomposition of bisphenol A and phenol, respectively. The presence of the hydrophobic modifier inhibited the generation of hydroxyl radicals and led to the photocatalysis undergoing mainly from partition followed by chemisorption and interfacial charge transfer. Partition and interfacial charge transfer were the rate determining steps for the degradation of phenol and bisphenol A, respectively. According to the Langmuir-Hinshelwood model, the adsorption coefficient (K,) and intrinsic rate constant (k(r)) for phenol were 4.17 x 10(-2) l/mg and 5.60 x 10(-2) mg-g/l-min-m(2), respectively, while they were 2.91 x 10(-2) l/m and 2.18 x 10(-1) mg-g/l-min-m(2), respectively for bisphenol A degradation. The product of the k(r) and k(a) for bisphenol A was 2.7 times higher than that for phenol, revealing that the modified TiO(2) favored decomposition of the compound which contains high chemiadsorbability and direct photocatalytic tendency in their individual systems. In contrast, the high degradable capability of phenol resulted in its preferential degradation in the competitive system. (C) 2009 Elsevier B.V. All rights reserved.