Browsing by Author "Weng, Sheng-Feng"

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A quaternary germanium(II) phosphate, Na[Ge-4(PO4)(3)]
(2008-03-01)
Lee, Chi-Shen
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Weng, Sheng-Feng
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應用化學系
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應用化學系分子科學碩博班
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Department of Applied Chemistry
A new germanium(II) phosphate, sodium tetragermanium tris( phosphate), Na[Ge-4(PO4)(3)], has been synthesized by a solid-state reaction. The compound is isotypic with [Sn-4(PO4)(3)] (A=Na, K, NH4). It features a [Ge-4(PO4)(3)](-) framework made up of GeO3 pyramids and PO4 tetrahedra, which are linked by shared corners, yielding a three-dimensional structure. The crystal studied showed partial inversion twinning.
Autothermal steam reforming of ethanol over La2Ce2-xRuxO7 (x=0-0.35) catalyst for hydrogen production
(2013-05-02)
Weng, Sheng-Feng
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Wang, Yun-Hsin
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Lee, Chi-Shen
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應用化學系
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Department of Applied Chemistry
Pyrochlore phases solid solutions, La2Ce2-xRuxO7 (x=0-0.35) were prepared with a sol-gel process and used as catalysts for the autothermal steam reforming of ethanol. The samples as prepared were characterized with powder X-ray diffraction (PXRD), X-ray photoelectron spectra (XPS), and temperature-programmed reduction (TPR). The XPS and TPR spectra revealed the effect of doped Run+ to oxidation states of La and Ce sites. The low temperature reduction ability and relative concentration of Ce4+ ions are increased as the cell-dimension decreased. Tests of catalytic activity showed that the reforming performance of La2Ce2-xRuxO7 catalysts was affected by the Ru/Ce loading ratio. For all catalysts, partial oxidation was favored at a large C/O composition; incomplete ethanol conversion was observed for C/O >= 0.7. The optimized catalyst was La2Ce1.8Ru0.2O7 with hydrogen production rate (r(H2)) 2.01 x 10(-3) mol s(-1) g(cat)(-1) (autothermal temperature similar to 600 degrees C and 97% ethanol conversion at C/O=0.6). The catalyst exhibited stable r(H2) over 26 h of the reaction with ethanol conversion >95%. r(H2) of the catalyst gradually decreased thereafter because LaAlO3 started to formed and affected catalytic process. For the catalyst, the Ru ions remained well dispersed before and after the AESR reaction. (C) 2013 Elsevier B.V. All rights reserved.
Controlled growth of beta-Na0.24V2O5 nanowire thin films
(2012-10-01)
Ke, Jhih-Syuan
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Wu, Ming-Cheng
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Weng, Sheng-Feng
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Lee, Chi-Shen
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應用化學系
A method to prepare well-aligned beta-Na0.24V2O5 nanowires (NWs) involves the deposition of a vanadium oxide complex onto a substrate via gaseous transport, followed by a reaction between the complex and a sodium cation (Na+) precursor coated on the substrate. Techniques to investigate the composition, crystallinity, and morphology of products as prepared include ICP-AES, X-ray powder diffraction (PXRD), SEM/transmission electron microscope (TEM), and XPS. PXRD patterns and images from a TEM confirm the single-crystalline nature of beta-Na0.24V2O5 NWs, which grow along direction [1 0 0]. Factors affecting the amount of deposited material and morphology were tested. On varying the reaction conditions, the length of the beta-Na0.24V2O5 wires is controlled in a range of 5-25 mu m. A mechanism of formation is proposed. According to measurements of field emission, the turn-on field is 7.8 V/mu m, and the maximum emission current density of 4.66 mA/cm(2) occurs at field 11 V/mu m. This method is applicable to grow other tertiary metal oxide nanostructures on glass substrate.
Controlled synthesis of VO2(R), VO2(B), and V2O3 vanadium-oxide nanowires
(2013-07-01)
Ke, Jhih-Syuan
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Weng, Sheng-Feng
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Wu, Ming-Cheng
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Lee, Chi-Shen
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應用化學系
Vanadium-oxide nanowires (NWs) V2O5, VO2(R), VO2(B), and V2O3 are deposited on a substrate to study their field-emission properties. V2O5 NWs are prepared by thermal evaporation via vapor transport of a vanadium-oxide complex under mild conditions. Films of VO2 and V2O3 wires are subsequently prepared by reducing V2O5 one-dimensional nanocrystals at 450 degrees C with hydrogen gas. The composition of the flowing H-2/Ar mixture and the duration of reduction are utilized to control the formation of VO2(R) or VO2(B) NWs. The crystallinity and morphology of products as prepared are characterized using several techniques, including powder X-ray diffraction, a scanning electron microscope, and a transmission electron microscope. The field-emission properties of the vanadium-oxide NWs as prepared exhibit a turn-on field of 4.56-7.65 V/mu m and an emission current density up to 3.68-8.36 mA/cm(2). These features indicate that vanadium-oxide NWs have potential FE emitter applications.
Enhanced catalytic activity of Ce(1-x)M(x)O(2) (M = Ti, Zr, and Hf) solid solution with controlled morphologies
(2010-01-01)
Chen, Wei-Ta
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Chen, Kuei-Bo
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Wang, Ming-Fang
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Weng, Sheng-Feng
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Lee, Chi-Shen
Ce(1-x)M(x)O(2) (M = Ti, Zr, and Hf) nanomaterials with controlled morphology and composition were synthesized by a two-step route for the first time. These nanomaterials exhibit high activities for hydrogen reduction and ethanol reforming reactions, and therefore, they may be useful for applications in catalysis and solid oxide fuel cells.
Enhanced catalytic activity of Ce1-xMxO2 (M = Ti, Zr, and Hf) solid solution with controlled morphologies
(2010-01-01)
Chen, Wei-Ta
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Chen, Kuei-Bo
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Wang, Ming-Fang
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Weng, Sheng-Feng
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Lee, Chi-Shen
Ce1-xMxO2 (M = Ti, Zr, and Hf) nanomaterials with controlled morphology and composition were synthesized by a two-step route for the first time. These nanomaterials exhibit high activities for hydrogen reduction and ethanol reforming reactions, and therefore, they may be useful for applications in catalysis and solid oxide fuel cells.
Hydrogen production from oxidative steam reforming of ethanol on nickel-substituted pyrochlore phase catalysts
(2017-02-02)
Weng, Sheng-Feng
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Hsieh, Ho-Chen
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Lee, Chi-Shen
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應用化學系
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Department of Applied Chemistry
A series of Ni-substituted pyrochlore oxides of La2Ce2-x NixO(7-delta) (x = 0.0-0.45) is prepared and their catalytic performance is studied. All compounds are characterized by X-ray powder diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS) and temperature-programmed reduction (TPR). Based on the XRD and XPS analyses, Ni is incorporated into the pyrochlore structure and induces the formation of Ce3+ ions. The reduction behavior and catalytic performance are directly related to the Ni content. The H-2 consumption in the TPR and H-2 production increases with the increased Ni content. The catalytic properties of these catalysts in the oxidative steam reforming of ethanol (OSRE) are investigated. The highest catalytic activity is obtained for the x = 0.45 sample, with a hydrogen selectivity of 82.60(5)% and the most stable catalyst is x = 0.2 with an average hydrogen selectivity of 79.0(4)%. The improved catalytic behavior can be attributed to the synergetic effect of cerium and nickel ions in the pyrochlore framework, which induces oxygen vacancies and reduces carbon formation. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Hydrogen production from oxidative steam reforming of ethanol on pyrochlore-type metal oxide, La2Ce2-xNi0.5xO7-1.5x (x=0.1-0.9)
(2012-01-01)
Weng, Sheng-Feng
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Lee, Chi-Shen
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應用化學系
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Department of Applied Chemistry
Oxidative steam reforming of ethanol is an effective way to produce high yields of hydrogen. A novel series of pyrochlore-type metal oxide of La2Ce2-xNi0.5xO7-1.5x (x=0.1-0.9) was prepared and its catalytic performance was studied. All the materials were characterized by X-ray powder diffraction (PXRD), inductively coupled plasma atomic emission spectrometer (ICP-AES) and temperature-programmed reduction (TPR). Catalytic performance was affected by the Ni content and the hydrogen selectivity reached the highest value of 80% for sample of x=0.9.
New metal-organic frameworks of [M(C6H5O7)(C6H6O7)(C6H7O7)(H2O)] center dot H2O (M=La, Ce) and [Ce-2(C2O4)(C6H6O7)(2)] center dot 4H(2)O
(2012-04-01)
Weng, Sheng-Feng
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Wang, Yun-Hsin
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Lee, Chi-Shen
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應用化學系
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Department of Applied Chemistry
Two novel materials, [M(C6H5O7)(C6H6O7)(C6H7O7)(H2O)] center dot H2O (M=La(1a), Ce(1b)) and [Ce-2(C2O4) (C6H6O7)(2)] center dot 4H(2)O (2), with a metal-organic framework (MOF) were prepared with hydrothermal reactions and characterized with photoluminescence, magnetic susceptibility, thermogravimetric analysis and X-ray powder diffraction in situ. The crystal structures were determined by single-crystal X-ray diffraction. Compound 1 crystallized in triclinic space group P (1) over bar (No. 2); compound 2 crystallized in monoclinic space group P2(1)/c (No. 14). The structure of 1 is built from a 1D MOF, composed of deprotonated citric ligands of three kinds. Compound 2 contains a 2D MOF structure consisting of citrate and oxalate ligands; the oxalate ligand arose from the decomposition in situ of citric acid in the presence of Cu-II ions. Photoluminescence spectra of compounds 1b and 2 revealed transitions between the 5d(1) excited state and two levels of the 4f(1) ground state (F-2(5/2) and F-2(7/2)). Compounds 1b and 2 containing Ce-III ion exhibit a paramagnetic property with weak antiferromagnetic interactions between the two adjacent magnetic centers. (C) 2012 Elsevier Inc. All rights reserved.
Oxidative steam reforming of ethanol over MxLa2-xCe1.8Ru0.2O7-delta (M = Mg, Ca) catalysts: effect of alkaline earth metal substitution and support on stability and activity
(2019-12-02)
Hsieh, Ho-Chen
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Tsai, Ping-Wen
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Chang, Yuan-Chia
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Weng, Sheng-Feng
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Sheu, Hwo-Shuenn
Alkaline earth metal substitutions on the A-site of pyrochlore oxide MxLa2-xCe1.8Ru0.2O7-delta (M = Mg, Ca) were studied as catalyst materials for oxidative/autothermal steam reforming of ethanol (OSRE/ATR). The as-prepared oxides were synthesized by a combustion method and characterized using powder X-ray diffraction (PXRD), and X-ray photoelectron and absorption spectroscopy (XPS and XAS). PXRD Rietveld analysis and elemental analysis (ICP-AES) support the formation of a pyrochlore-type structure (space group Fd3m) with a distorted coordination environment. The substitution of Mg²⁺ and Ca²⁺ ions affects the oxidation states of Ce^4+/3+ and Ruⁿ⁺ ions and creates oxygen vacancies, which leads to enhanced catalytic activity and reduced ethylene selectivity. A long-term stability test showed optimized catalysts Mg0.3La1.7Ce1.8Ru0.2O7-delta and Ca0.2La1.8Ce1.8Ru0.2O7-delta with SH2 = 101(1)% and SH2 = 91(2)% under OSRE conditions. The initial operation temperatures were lower than that of the unsubstituted catalyst La2Ce1.8Ru0.2O7-delta. Catalysts supported on La2Zr2O7 showed stable OSRE/ATR performance and low carbon deposition compared to catalysts supported on Al2O3. We ascribe the enhanced activity to well-dispersed alkaline earth metal and Ru ions in a solid solution structure, synergistic effects of (Mg, Ca)²⁺/Ce^3+/4+/Ruⁿ⁺ ions, and a strong catalyst-support interaction that optimized the ethanol conversion and hydrogen production.
Ruthenium substituted pyrochlore metal oxide catalysts Y2Ce2-xRuxO7-delta (x=0-0.4) for oxidative steam reforming of ethanol
(2020-07-31)
Hsieh, Ho-Chen
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Chen, Yun-Sheng
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Weng, Sheng-Feng
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Hsieh, Yu-Ping
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Lee, Chi-Shen
Metal oxides Y2Ce2-xRuxO7-delta (x = 0-0.4) with partial substitution of Run+ cations in the host structure were synthesized to study their catalytic activity on oxidative steam reforming of ethanol (OSRE). The samples were characterized using X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and temperature-programmed reduction (TPR). The performances investigated by varied temperatures, Ru ion content, carbon-to-oxygen ratios and long-term stability. The lowest activation temperature on OSRE is 300 degrees C, which is significantly lower than that of La2Ce2-xRuxO7-delta (400 degrees C). The cell dimension of Y2Ce2-xRuxO7-delta was reduced compare to La2Ce2-xRuxO7-delta for the replacement of the Y3+ ion with La3+ ion. The reduced unit cell in the host structure not only increase the surface composition of the Ce4+ ions, but also induce the synergetic effect of Run+/Ru4+ (n > 4) and Ce4+/Ce3+, which lead to the enhanced OSRE activity. The optimized catalyst Y2Ce1.6Ru0.4O7-delta showed selectivity of hydrogen S-H2 = 84(4)% (Y-H2 = 2.5(1) mol/mol EtOH) and carbon monoxide S-CO = 48(1)% for long-term stability test at T = 300 degrees C, C/O = 0.5, and O-2/C2H5OH = 1.5. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Synthesis and characterization of alkali-metal tin(II) phosphates: Na(10)Sn(31)(HPO(4))(6)(P(2)O(7))(6)(PO(4))(12) and K(2)SnP(2)O(7)
(2008-11-01)
Weng, Sheng-Feng
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Chen, Kuei-Bo
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Lee, Chi-Shen
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應用化學系
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應用化學系分子科學碩博班
Two new alkali-metal tin(II) phosphates - Na(10)Sn(31)(HPO(4))(6)(P(2)O(7))(6)(PO(4))(12) (1) and K(2)SnP(2)O(7) (2) - were synthesized by high-temperature reactions and structurally characterized by single-crystal X-ray diffraction. Na(10)Sn(31)(HPO(4))(6)(P(2)O(7))(6)(PO(4))(12) crystallized in the noncentrosymmetric space group P-62c (No. 190) with a = 9.6445(1) angstrom, b = 9.6445(1) angstrom, c = 34.059(6) angstrom, V = 2743.6(7) angstrom(3) and Z = 1. K(2)SnP(2)O(7) crystallized in the monoclinic space group P2(1)/n with a = 9.856(3) angstrom, b = 6.7244(1) angstrom, c = 12.225(3) angstrom, beta = 108.240(5)degrees, V = 769. 5(3) angstrom(3) and Z = 4. Both structures exhibit a novel open-framework structure. The crystal structure of 1 contains SnO(3) and SnO(4) polyhedra sharing comers with [HPO(4)](2-), [PO(4) ](3-) and [P(2)O(7)](4-) groups, which form tunnels of six rings filled with Na(+) cations and parallel to the c-axis, which are connected via O-Sn-O bridges to form a three-dimensional open framework. The crystal structure of 2 contains SnO(4) seesaw polyhedra sharing comers with diphosphate groups to form a three-dimensional [SnP(2)O(7)](2-) framework that exhibits a tunnel structure of 10- and 12- membered rings expanding along [011] and [100] with four arrays of K(+) cations located in channels of the framework. (c) 2008 Elsevier Masson SAS. All rights reserved.