Browsing by Author "Tsao, Chun-Wen"

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Enhanced photoelectrochemical hydrogen generation in neutral electrolyte using non-vacuum processed CIGS photocathodes with an earth-abundant cobalt sulfide catalyst
(2019-02-28)
Wang, Mingqing
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Chang, Yung-Shan
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Tsao, Chun-Wen
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Fang, Mei-Jing
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Hsu, Yung-Jung
This work reports the novelty of using eco-friendly and cost-effective non-vacuum Electrostatic Spray-Assisted Vapour Deposited Cu(In, Ga) SSe (CIGS) thin films as photocathodes, combined with the earth abundant cobalt sulfide (Co-S) as a catalyst to accelerate the kinetics of photogenerated electron transfer and hydrogen generation for photoelectrochemical water splitting. CdS and ZnO layers were subsequently deposited on top of the selenised CIGS films to increase the charge separation and lower the charge recombination for the photocathodes. In order to improve the lifetime and scalability of the CIGS photocathode and the other cell components, a photoelectrochemical test was conducted in a neutral electrolyte of 0.5 M Na2SO4 under simulated sunlight (AM 1.5G). Both the photocurrent densities and the onset potentials of the photocathodes were significantly improved by the electro-deposition of the low cost and earth-abundant Co-S catalyst, with a photocurrent density as high as 19.1 mA cm(-2) at -0.34 V vs. reversible hydrogen electrode (RHE), comparable with and even higher than that of the control photocathode using rare and precious Pt as a catalyst.
Nitrogen-Doped Graphene Quantum Dots for Remarkable Solar Hydrogen Production
(2020-06-22)
Tsai, Kai-An
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Hsieh, Ping-Yen
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Lai, Ting-Hsuan
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Tsao, Chun-Wen
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Pan, Hui
We synthesized nitrogen (N)-doped graphene quantum dots (N-GQDs) using a top-down hydrothermal cutting approach. The concentration of N dopants was readily controlled by adjusting the concentration of the N source of urea. When N dopants were incorporated into GQDs, visible absorption was induced by C-N bonds, which created another pathway for generating photoluminescence (PL). Time-resolved PL data revealed that the carrier lifetime of GQDs was increased upon doping with the optimized N concentration. The photoelectrochemical properties of N-GQDs toward water splitting were studied, and the results showed that 2N-GQDs prepared with 2 g of urea produced the highest photocurrent. The photocatalytic activity of 2N-GQDs powder photocatalyst for hydrogen production was also examined under AM 1.5G illumination, showing substantial enhancement over that of pristine GQDs. Electrochemical impedance spectroscopy data further revealed a significant improvement in charge dynamics and reaction kinetics and an increased carrier concentration as a result of N doping.
Reduced graphene oxides-wrapped ZnO with notable photocatalytic property
(2020-07-01)
Hu, Wei-Chen
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Chen, Yi-An
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Hsieh, Ping-Yen
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Tsao, Chun-Wen
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Chiu, Yi-Hsuan
A facile, environmentally benign antisolvent method has been developed to prepare for reduced graphene oxides (RGO)-wrapped ZnO nanocrystals with controlled RGO contents. Because of the high electrical conductivity of RGO, the photogenerated electrons at ZnO mostly transported to RGO, leaving positively charged photoexcited holes in ZnO to result in charge separation. The steady-state photoluminescence, time-resolved photoluminescence spectroscopy and photovoltage decay analysis were employed to investigate charge carrier dynamics and charge transfer behaviors of RGO-ZnO. The influence of RGO content on the charge dynamics and photoconversion efficiency of RGO-ZnO toward dye degradation and water splitting has been realized. (C) 2020 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
Semiconductor nanoheterostructures for photoconversion applications
(2020-04-01)
Fang, Mei-Jing
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Tsao, Chun-Wen
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Hsu, Yung-Jung
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交大名義發表
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材料科學與工程學系
The ever-growing energy crisis and environmental degradation have instigated scientists to explore sophisticated, versatile energy conversion systems. Photoconversion, which conveys solar power to chemical energy, has emerged as an eminent energy conversion approach to accomplish the demands. Recent years have seen the rocketing rise of semiconductor heterostructures as an ideal material paradigm for the realization of miscellaneous photoconversion applications ranging from water splitting, CO2 reduction and environmental purification to photosynthesis. With tailored functionalities from synergetic effects, semiconductor heterostructures come into prominence as the forefront of photocatalyst development. This topical review summarizes the photoconversion applications developed so far by employing semiconductor heterostructures, with a focus on the heterostructure design principle, interfacial charge dynamics and key factors dictating the overall performance. Future research outlooks and perspectives on the progress of photoconversion technology are also presented.
Shape-Tunable SrTiO3 Crystals Revealing Facet-Dependent Optical and Photocatalytic Properties
(2019-06-06)
Hsieh, Pei-Lun
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Naresh, Gollapally
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Huang, Yu-Sheng
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Tsao, Chun-Wen
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Hsu, Yung-Jung
SrTiO3 cubes with tunable sizes of 160-290 nm have been synthesized by mixing TiCl4, SrCl2, and LiOH in pure ethanol or a water/ethanol mixed solution at just 70 degrees C for 3 h. Replacing water/ethanol with water/hexanol and water/ethylene glycol, and fine tuning the amounts of other reagents, resulted in the formation of edge-truncated cubes and {100}-truncated rhombic dodecahedra, respectively. X-ray diffraction and transmission electron microscopy characterization, supported by Rietveld refinement analysis, have revealed shape-dependent tuning in lattice parameters. The cubes display slight size-related optical band shifts, and they show clearly more blue-shifted light absorption than the other particles exposing significant {110} faces. The {100}-truncated rhombic dodecahedra are far more efficient than cubes at photodegradation of methylene blue and photocatalyzed hydrogen evolution from water in the presence of methanol. The photocatalytic activity variation should arise from different degrees of surface band bending for the {100} and {110} faces of SrTiO3, suggesting surface facet control as a strategy for enhancing photocatalyzed hydrogen production.
TiO2-Au-Cu2O Photocathodes: Au-Mediated Z-Scheme Charge Transfer for Efficient Solar-Driven Photoelectrochemical Reduction
(2018-12-01)
Li, Jing-Mei
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Tsao, Chun-Wen
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Fang, Mei-Jing
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Chen, Chun-Chi
;
Liu, Chen-Wei
An Au-mediated Cu2O-based Z-scheme heterostructure system is demonstrated for use as efficient photocathodes in photoelectrochemical (PEC) reduction. The samples are prepared by electrodepositing a Cu2O layer on the surface of Au particle-coated TiO2 nanorods. For TiO2-Au-Cu2O, the embedded Au particles function as a charge transfer mediator to enhance the electron transportation from the conduction band of TiO2 to the valence band of Cu2O. Such a vectorial charge transfer leads to the concentration of electrons at the conduction band of Cu2O and the collection of holes at the valence band of TiO2, providing TiO2-Au-Cu2O with substantially high redox abilities for reduction applications. Time-resolved photoluminescence spectra and electrochemical impedance spectroscopy analysis suggest that interfacial charge transfer is significantly improved because of the Au-mediated Z-scheme charge transfer mechanism. By virtue of the high redox ability and improved interfacial charge transfer, TiO2-Au-Cu2O performs much better as a photocathode in H2 production and CO2 reduction than pure Cu2O and binary TiO2-supported Cu2O do. Remarkably, the photocurrent density of TiO2-Au-Cu2O toward PEC CO2 reduction can reach as high as -1.82 mA/cm(2) at +0.11 V vs RHE. The incident photon-to-current conversion efficiency data manifest that TiO2-Au-Cu2O surpasses both pure Cu2O and binary TiO2-supported Cu2O in PEC reduction across the whole photoactive region. The current study paves a valuable approach of devising Z-scheme photocathode for the construction of sophisticated artificial photosynthesis systems capable of solar-to-fuel conversion.