Browsing by Author "Nguyen, An T."

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Au-decorated GaOOH nanorods enhanced the performance of direct methanol fuel cells under light illumination
(2016-05-15)
Hsu, Yi-Han
;
Nguyen, An T.
;
Chiu, Yi-Hsuan
;
Li, Jing-Mei
;
Hsu, Yung-Jung
We reported for the first time that GaOOH nanorods, which were prepared using a facile chemical precipitation method, may display noticeable photocatalytic activities toward methanol oxidation under light illumination, a significant revelation for demonstrating their use as the anode photocatalyst in the half cell reaction of direct methanol fuel cells (DMFCs). The GaOOH nanorods were further decorated with Au nanoparticles to endow them with increasingly pronounced charge separation, which conduced to a remarkable enhancement in the photocatalytic performance. Time-resolved photoluminescence spectroscopy was employed to depict the charge transfer event across the interface of GaOOH/Au, from which a correlation between photocatalytic efficiency and interfacial charge dynamics was realized. By incorporating GaOOH nanorods into the traditional Pt-catalyzed half-cell reaction, a 12.7% increase in anodic current generation can be attained under light illumination, demonstrating the promising potential of GaOOH as a practical anode photocatalyst in DFMCs. A further enhancement in methanol oxidation current up to 70.8% can be achieved by employing Au-decorated GaOOH nanorods, which was attributed to the efficient charge carrier transfer rendered by the Au decoration. The current study delivers both fundamental and practical importance as it broadens the scope of electrocatalysts for fuel cells, specifically by introducing a new class of highly efficient photocatalysts for promoting electrochemical reactions. (C) 2015 Elsevier B.V. All rights reserved.
First demonstration of rainbow photocatalysts using ternary Cd1-xZnxSe nanorods of varying compositions
(2014-04-22)
Nguyen, An T.
;
Lin, Wei-Hao
;
Lu, Yi-Hsuan
;
Chiou, Yao-De
;
Hsu, Yung-Jung
We demonstrated for the first time that the assembly of Cd1-xZnxSe nanorods (NRs) with five compositions (x= 0, 0.35, 0.54, 0.61,1) may absorb the whole visible spectrum in a gradient fashion for photoconversion applications. The samples were prepared by conducting cation exchange reactions on Ag2Se NRs with excess Cd2+ and Zn2+ ions. By modulating the molar ratio of Cd2+ to Zn2+ employed, the composition of the resulting Cd1-xZnxSe NRs can be delicately controlled. Because of the tunability of band edge with stoichiometry, Cd1-xZnxSe NRs of varying compositions absorbed light at different wavelength regions, which spanned almost the entire visible spectrum. As compared to the individual constituent NRs, the NRs assembly exhibited greatly improved photoactivity in photoelectrochemical water splitting as well as superior photocatalytic performance toward methylene blue degradation under white light illumination. This superiority emanates from the composition-gradient configuration that significantly improves the light harvesting efficiency by absorbing almost the whole visible spectrum of the incident white light. The full visible photon harvesting of the NRs assembly was validated by the photocurrent action spectrum which showed spectral accordance with the absorption spectrum. The recycling test manifests that the NRs assembly displayed substantially high stability during its use as photocatalyst. Furthermore, the result of performance evaluation under natural sunlight reveals that the present NRs assembly can be used as practical rainbow photocatalysts which may effectively harvest energy from sunlight. The demonstration from this work may facilitate the use of sophisticated assembly of semiconductor nanocrystals in relevant photoconversion processes where the effectiveness of photon harvesting is determinant. (C) 2014 Elsevier B.V. All rights reserved.