Browsing by Author "Lu, I-Te"

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Dealloyed Pt2Os nanoparticles for enhanced oxygen reduction reaction in acidic electrolytes
(2014-05-05)
Lee, Yi-Juei
;
Hsieh, Yu-Chi
;
Tsai, Ho-Cheng
;
Lu, I-Te
;
Wu, Yue-Han
Carbon-supported Pt2Os (Pt2Os/C) nanoparticles in 3.55 nm sizes are synthesized from a wet chemical reflux process. Subsequently, the Pt2Os/C undergoes a dealloying treatment in which multiple cyclic voltammetric scans are imposed to dissolve the Os atoms selectively from the surface of the Pt2Os nanoparticles. X-ray diffraction signals from the dealloyed sample (DA-Pt2Os/C) indicate a fcc phase and composition analysis suggests Pt4Os. Line scans from the scanning transmission electron microscope confirm that the surface of Pt4Os is depleted with the Os atoms. This agrees with our quantum mechanics (Density Funtional theory) calculations, which predict for the Pt3Os composition that the surface skin layer is pure Pt. The DA-Pt2Os/C shows impressive electrocatalytic behaviors (0.29 mA mu g(Pt)(-1) in mass activity and 1.03 mA cm(Pt)(-2) in specific activity) for the oxygen reduction reaction (ORR) in oxygen-saturated 0.1 M aqueous HClO4 solution, as compared to those of commercially available Pt/C and as-synthesized Pt2Os/C. In stability test, the DA-Pt2Os/C demonstrates a better retention of ORR activities and a smaller loss of electrochemical active surface area. We verify experimentally that a four-electron step is responsible for the ORR process occurring on the DA-Pt2Os/C. (C) 2014 Elsevier B.V. All rights reserved.
EQCM Study on Pulse Current Pt Electrodeposition
(2015-12-01)
Lu, I-Te
;
Hsieh, Yu-Chi
;
Chen, Po-Chun
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Wu, Pu-Wei
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材料科學與工程學系
Electrochemical Quartz Crystal Microbalance (EQCM) was used to investigate the events occurring during current-on (T-on) and current-off (T-off) for pulse current electrodeposition of Pt in both air and Ar atmospheres. The EQCM profiles indicated a transient mass loss when the current was turned on, followed by a linear mass gain associated with the Pt electrodeposition from the H2PtCl6 plating bath. During the T-off, the mass revealed a steady increase until it leveled off after 10 sec. The minute transient mass loss during the initial stage of T-on was attributed to the reduction of the adsorbed PtCl62- whereas the mass gain during the T-off was due to the absorption of PtCl62- onto the freshly-deposited Pt surface. In air atmosphere, the parasitic oxygen reduction reaction consumed part of the reduction current and thus, reduced the Pt plating efficiency by 6%. In addition, smaller mass gains during T-off and T-on were observed for the Pt plating in air atmosphere.
High-yield water-based synthesis of truncated silver nanocubes
(2014-02-15)
Chang, Yun-Min
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Lu, I-Te
;
Chen, Chih-Yuan
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Hsieh, Yu-Chi
;
Wu, Pu-Wei
A high-yield water-based hydrothermal synthesis was developed using silver nitrate, ammonia, glucose, and cetyltrimethylammonium bromide (CTAB) as precursors to synthesize truncated silver nanocubes with uniform sizes and in large quantities. With a fixed CTAB concentration, truncated silver nanocubes with sizes of 49.3 +/- 4.1 nm were produced when the molar ratio of glucose/silver cation was maintained at 0.1. The sample exhibited (100), (110), and (111) planes on the facets, edges, and corners, respectively. In contrast, with a slightly larger glucose/silver cation ratio of 0.35, well-defined nanocubes with sizes of 70.9 +/- 3.8 nm sizes were observed with the (100) plane on six facets. When the ratio was further increased to 1.5, excess reduction of silver cations facilitated the simultaneous formation of nanoparticles with cubic, spherical, and irregular shapes. Consistent results were obtained from transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and UV-visible absorption measurements. (C) 2013 Elsevier B. V. All rights reserved.
Surface modification of commercial PtRu nanoparticles for methanol electro-oxidation
(2013-10-15)
Kuo, Che-Wei
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Lu, I-Te
;
Chang, Li-Chung
;
Hsieh, Yu-Chi
;
Tseng, Yuan-Chieh
The surfaces of commercially available PtRu nanoparticles (PtRu/C) have been successfully modified via a displacement reaction between the Ru atoms on the PtRu/C and the Pt ions in an aqueous hexachloroplatinic acid solution. The concentration of the hexachloroplatinic acid solution was deliberately formulated to allow for the formation of sub-monolayered Pt (Pt(1/16)) and monolayered Pt (Pt(1/8)) on the surface of PtRu/C. Material characterization, including X-ray diffraction patterns and transmission electron microscopy images, showed that the PtRu phases of the samples were identical but that the particle sizes increased slightly after the surface modification. Data from inductively coupled plasma mass spectrometry confirmed the deposition of Pt with negligible loss of Ru. X-ray absorption spectroscopy showed Pt-enriched surfaces, and the surface Pt content decreased in the order Pt(1/8) > Pt(1/16) > PtRu/C. Cyclic voltammetry and chronoamperometry were conducted for methanol electro-oxidation, and our results indicated impressive catalytic ability and carbon monoxide tolerance for Pt(1/16), followed by Pt(1/8) and PtRu/C. The mass activities of Pt(1/16) and Pt(118) increased 223% and 135% over that of PtRu/C. We attributed the observed improvements to the reduced amount of Ru on the PtRu surface, which resulted in an optimized PtRu ratio with enhanced catalytic ability. (C) 2013 Elsevier B.V. All rights reserved.