Browsing by Author "Hsu, Yung-Jung"

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A facile green antisolvent approach to Cu2+-doped ZnO nanocrystals with visible-light-responsive photoactivities
(2014-08-07)
Lu, Yi-Hsuan
;
Lin, Wei-Hao
;
Yang, Chao-Yao
;
Chiu, Yi-Hsuan
;
Pu, Ying-Chih
An environmentally benign antisolvent method has been developed to prepare Cu2+-doped ZnO nanocrystals with controllable dopant concentrations. A room temperature ionic liquid, known as a deep eutectic solvent (DES), was used as the solvent to dissolve ZnO powders. Upon the introduction of the ZnO-containing DES into a bad solvent which shows no solvation to ZnO, ZnO was precipitated and grown due to the dramatic decrease of solubility. By adding Cu2+ ions to the bad solvent, the growth of ZnO from the antisolvent process was accompanied by Cu2+ introduction, resulting in the formation of Cu2+-doped ZnO nanocrystals. The as-prepared Cu2+-doped ZnO showed an additional absorption band in the visible range (400-800 nm), which conduced to an improvement in the overall photon harvesting efficiency. Time-resolved photoluminescence spectra, together with the photovoltage information, suggested that the doped Cu2+ may otherwise trap photoexcited electrons during the charge transfer process, inevitably depressing the photoconversion efficiency. The photoactivity of Cu2+-doped ZnO nanocrystals for photoelectrochemical water oxidation was effectively enhanced in the visible region, which achieved the highest at 2.0 at% of Cu2+. A further increase in the Cu2+ concentration however led to a decrease in the photocatalytic performance, which was ascribed to the significant carrier trapping caused by the increased states given by excessive Cu2+. The photocurrent action spectra illustrated that the enhanced photoactivity of the Cu2+-doped ZnO nanocrystals was mainly due to the improved visible photon harvesting achieved by Cu2+ doping. These results may facilitate the use of transition metal ion-doped ZnO in other photoconversion applications, such as ZnO based dye-sensitized solar cells and magnetism-assisted photocatalytic systems.
A facile green antisolvent approach to Cu2+-doped ZnO nanocrystals with visible-light-responsive photoactivities
(2014-08-07)
Lu, Yi-Hsuan
;
Lin, Wei-Hao
;
Yang, Chao-Yao
;
Chiu, Yi-Hsuan
;
Pu, Ying-Chih
An environmentally benign antisolvent method has been developed to prepare Cu2+-doped ZnO nanocrystals with controllable dopant concentrations. A room temperature ionic liquid, known as a deep eutectic solvent (DES), was used as the solvent to dissolve ZnO powders. Upon the introduction of the ZnO-containing DES into a bad solvent which shows no solvation to ZnO, ZnO was precipitated and grown due to the dramatic decrease of solubility. By adding Cu2+ ions to the bad solvent, the growth of ZnO from the antisolvent process was accompanied by Cu2+ introduction, resulting in the formation of Cu2+-doped ZnO nanocrystals. The as-prepared Cu2+-doped ZnO showed an additional absorption band in the visible range (400-800 nm), which conduced to an improvement in the overall photon harvesting efficiency. Time-resolved photoluminescence spectra, together with the photovoltage information, suggested that the doped Cu2+ may otherwise trap photoexcited electrons during the charge transfer process, inevitably depressing the photoconversion efficiency. The photoactivity of Cu2+-doped ZnO nanocrystals for photoelectrochemical water oxidation was effectively enhanced in the visible region, which achieved the highest at 2.0 at% of Cu2+. A further increase in the Cu2+ concentration however led to a decrease in the photocatalytic performance, which was ascribed to the significant carrier trapping caused by the increased states given by excessive Cu2+. The photocurrent action spectra illustrated that the enhanced photoactivity of the Cu2+-doped ZnO nanocrystals was mainly due to the improved visible photon harvesting achieved by Cu2+ doping. These results may facilitate the use of transition metal ion-doped ZnO in other photoconversion applications, such as ZnO based dye-sensitized solar cells and magnetism-assisted photocatalytic systems.
A Facile Seed-Mediated Route to Au Nanoplates for SERS Application
(2011)
Lin, Wei-Hao
;
Hsu, Yung-Jung
;
材料科學與工程學系
;
Department of Materials Science and Engineering
We have successfully synthesized Au nanoplates using a seed-mediated approach. Without the size-selection process, the yield of nanoplates in the as-obtained product was as high as 80 %. The nanoplate samples were characterized with TEM, SAED, XRD, UV-VIS-NIR and SERS spectroscopy. The results of SERS analyses demonstrate the potential of the anisotropicaily-shaped Au nanoplates as an active platform for Raman-sensitive analyte molecules.
A more accurate, reliable method to evaluate the photoelectrochemical performance of semiconductor electrode without under/over estimation
(2018-03-20)
Li, Jing-Mei
;
Wang, Yu-Ting
;
Hsu, Yung-Jung
;
材料科學與工程學系
;
Department of Materials Science and Engineering
A more accurate and reliable method is proposed to evaluate the photoelectrochemical (PEC) performance of semiconductor toward water splitting. Conventionally, I-t measurements are conducted at a fixed potential relative to the reference electrode, e.g., 0 V vs. Ag/AgCl, to monitor the photocurrent, which has been regarded as a direct indicator for performance comparison among different electrodes. Considering that the open-circuit potential (OCP) varies from electrode to electrode, the photocurrent comparison at a fixed potential may misrepresent the actual differences between samples. Here, we study the PEC performance by applying two distinct external bias values, one at 0 V vs. Ag/AgCI deriving from the conventional practice and the other at 0.1 V vs. OCP representing the exactly fixed applied overpotential. Two experimental groups are designed to address the arguments, including the influence of heat treatment for ZnO nanorod arrays and the global comparison among ZnO, TiO2, Au particle-decorated TiO2, and CdS electrodes. Different trends in photocurrent are observed at the two distinct biases, with the results from 0.1 V vs. OCP conforming to the general considerations. The results suggest that application of a fixed potential relative to the OCP will provide a more fair comparison for accurate PEC performance evaluation without under-or over-estimation. (C) 2018 Elsevier Ltd. All rights reserved.
Ag-Nanoparticle-Decorated SiO2 Nanospheres Exhibiting Remarkable Plasmon-Mediated Photocatalytic Properties
(2012-09-06)
Chen, Kuang-Hsiu
;
Pu, Ying-Chih
;
Chang, Kao-Der
;
Liang, Yi-Fan
;
Liu, Chia-Ming
We demonstrated for the first time that Ag-nanoparticle-decorated SiO2 nanospheres (NSs) may display noticeable photocatalytic activities upon surface plasmon resonance (SPR) excitation. The samples were prepared by reacting SiO2 NSs with AgNO3 in the seed-mediated growth process, from which the Ag particle size and decoration density can be readily controlled. The dependence of the SPR-mediated photocatalytic performance of Ag-decorated SiO2 NSs on the Ag morphology was investigated and presented. The as-prepared Ag-decorated SiO2 NSs showed a significantly red shifted and relatively broad SPR absorption when compared with the individually dispersed Ag nanoparticles. Owing to the considerably broad SPR absorption that spanned from the visible to the near-infrared region, Ag-decorated SiO2 NSs surpassed N-doped P-25 TiO2 powder and individually dispersed Ag nanoparticles in photocatalytic activity, demonstrating their potential as an active photocatalyst in nearly all the current photocatalysis applications. Furthermore, the result of performance evaluation under natural sunlight shows that the present Ag-decorated SiO2 NSs can be used as highly efficient photocatalysts that may practically harvest energy from sunlight. The current study provides a new paradigm for designing plasmonic metal nanostructures that can effectively absorb the entire solar spectrum and beyond for solar fuel generation.
AgAu alloy nanoshell: Decorated BaTiO3/TiO2 and SrTiO3/TiO2 for photoelectrochemical catalysis
(2019-08-25)
Chang, Yung-Shan
;
Lee, T. Randall
;
Hsu, Yung-Jung
;
Medhi, Riddhiman
;
Srinoi, Pannaree
Anisotropic palladium nanocrystals as promising electrocatalysts
(2011-03-27)
Hsu, Yung-Jung
;
Fan, Yu-Sin
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Au nanoplates as robust, recyclable SERS substrates for ultrasensitive chemical sensing
(2014-03-15)
Lin, Wei-Hao
;
Lu, Yi-Hsuan
;
Hsu, Yung-Jung
;
材料科學與工程學系
;
Department of Materials Science and Engineering
With the structural advantages of being sharp and straight, Au nanoplates may work as a promising surface-enhanced Raman scattering (SERS) platform for detection of Raman-sensitive analytes. However, the utilization of Au nanoplates as realistic SERS substrates is still not widely investigated, especially in the practical detection of environmentally persistent pollutants. This work delivers the first successful demonstration of using Au nanoplate platform in practical SERS sensing toward a typical polycyclic aromatic hydrocarbons pollutant of pyrene. The samples were prepared using an environmentally benign seed-mediated growth approach without the post-purification treatment. It was found that Au nanoplates exhibited significantly enhanced SERS activities (enhancement factor = 7.30 x 10(7)) and achieved an extremely low detection limit (5 x 10(-10) M) toward pyrene molecules. Furthermore, the SERS activity of Au nanoplates can be fully recovered after repeatedly used and recycled in pyrene detection. These results manifest that the present Au nanoplates can serve as robust, recyclable SERS substrates that allow rapid detection of trace levels of analytes with a high degree of sensitivity and stability. The findings from this work may facilitate the use of Au nanoplate SERS substrates in more realistic applications such as biomolecule sensing and environmental monitoring. (C) 2013 Elsevier Inc. All rights reserved.
Au Nanostructure-Decorated TiO2 Nanowires Exhibiting Photoactivity Across Entire UV-visible Region for Photoelectrochemical Water Splitting
(2013-08-01)
Pu, Ying-Chih
;
Wang, Gongming
;
Chang, Kao-Der
;
Ling, Yichuan
;
Lin, Yin-Kai
Here we demonstrate that the photoactivity of Au-decorated TiO2 electrodes for photoelectrochemical water oxidation can be effectively enhanced in the entire UV-visible region from 300 to 800 nm by manipulating the shape of the decorated Au nanostructures. The samples were prepared by carefully depositing Au nanoparticles (NPs), Au nanorods (NRs), and a mixture of Au NPs and NRs on the surface of TiO2 nanowire arrays. As compared with bare TiO2, Au NP-decorated TiO2 nanowire electrodes exhibited significantly enhanced photoactivity in both the UV and visible regions. For Au NR-decorated TiO2 electrodes, the photoactivity enhancement was, however, observed in the visible region only, with the largest photocurrent generation achieved at 710 nm. Significantly, TiO2 nanowires deposited with a mixture of Au NPs and NRs showed enhanced photoactivity in the entire UV visible region. Monochromatic incident photon-to-electron conversion efficiency measurements indicated that excitation of surface plasmon resonance of Au is responsible for the enhanced photoactivity of Au nanostructure-decorated TiO2 nanowires. Photovoltage experiment showed that the enhanced photoactivity of Au NP-decorated TiO2 in the UV region was attributable to the effective surface passivation of Au NPs. Furthermore, 3D finite-difference time domain simulation was performed to investigate the electrical field amplification at the interface between Au nanostructures and TiO2 upon SPR excitation. The results suggested that the enhanced photoactivity of Au NP-decorated TiO2 in the UV region was partially due to the increased optical absorption of TiO2 associated with SPR electrical field amplification. The current study could provide a new paradigm for designing plasmonic metal/semiconductor composite systems to effectively harvest the entire UV visible light for solar fuel production.
Au-Cd1-xZnxS core-alloyed shell nanocrystals: boosting the interfacial charge dynamics by adjusting the shell composition
(2018-09-28)
Pu, Ying-Chih
;
Chen, Wei-Ta
;
Fang, Mei-Jing
;
Chen, Yu-Lin
;
Tsai, Kai-An
Au-Cd1-xZnxS core-shell nanocrystals (NCs) with controllable shell compositions (from x = 0 to x = 0.37) were synthesized by using the hot-injection method. By increasing the mole fraction of ZnS in the Cd1-xZnxS shell, the conduction band of Cd1-xZnxS can be cathodically shifted to cause an increase of energy difference between the conduction band level of the Cd1-xZnxS shell and the Fermi level of the Au core, thereby enlarging the driving force of interfacial electron transfer to enhance the photoelectrochemical (PEC) efficiency. The interfacial charge dynamics of the samples were examined by time-resolved photoluminescence (TRPL) spectroscopy. The results showed that the interfacial electron transfer rate constant (k(et)) from the Cd1-xZnxS shell to the Au core was increased by 2 orders of magnitude, from 2.41 x 10(7) to 4.91 x 10(9) s(-1) as the mole fraction of ZnS increased from 0 to 0.37. Furthermore, PEC characterization, including Mott-Schottky analysis and photovoltage decay measurements, illustrated that gradually introducing ZnS into the shell composition of Au-Cd1-xZnxS NCs can modify the band structure and enhance the effectiveness of interfacial ET for advancing the PEC properties. The practical use of Au-Cd1-xZnxS NCs in PEC methanol oxidation was also demonstrated, revealing their promising potential as viable photoelectrodes for various PEC applications. The present study delivers an alternative approach of modulating the interfacial ET dynamics of core-shell MSNs by means of shell composition adjustment. The illustrations provide an empirical guideline to the intelligent design of core-shell metal-semiconductor nanoheterostructures (MSNs) for the desired PEC applications.
Au-CdS Core-Shell Nanocrystals with Controllable Shell Thickness and Photoinduced Charge Separation Property
(2008-12-09)
Chen, Wei-Ta
;
Yang, Ting-Ting
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Hsu, Yung-Jung
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Au-decorated GaOOH nanorods enhanced the performance of direct methanol fuel cells under light illumination
(2016-05-15)
Hsu, Yi-Han
;
Nguyen, An T.
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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.
Au-decorated Na(x)H(2-x)Ti(3)O(7) nanobelts exhibiting remarkable photocatalytic properties under visible-light illumination
(2010-06-18)
Pu, Ying-Chih
;
Chen, Yu-Chih
;
Hsu, Yung-Jung
;
材料科學與工程學系
;
Department of Materials Science and Engineering
We demonstrated for the first time that Na-intercalated H(2)Ti(3)O(7) (Na(x)H(2-x)Ti(3)O(7)) NBs, prepared in the typical alkaline hydrothermal process, can effectively absorb visible light to carry out photocatalytic reactions. With the capability of effective light absorption in visible range, Na(x)H(2-x)Ti(3)O(7) NBs performed much better in the photoclegradation of thionine than the other three counterpart products including H(2)Ti(3)O(7), mixed Na(2)Ti(6)O(13)/TiO(2) and anatase TiO(2) under visible-light irradiations. As compared to the relevant commercial products like P-25 TiO(2) and Na(2)Ti(3)O(7) powders, the as-synthesized Na(x)H(2-x)Ti(3)O(7) NBs exhibited superior photocatalytic efficiency under UV illumination, demonstrating their potential as an efficient photocatalyst in relevant redox reactions. A further enhancement in the photocatalytic activity can be achieved for Na(x)H(2-x)Ti(3)O(7) NBs when Au nanoparticles of suitable amount were deposited on their surfaces. This improvement is due to the band offsets between Na(x)H(2-x)Ti(3)O(7) and Au, which may promote charge carrier separation to favor the photocatalysis. The recycling test reveals that Au-decorated Na(x)H(2-x)Ti(3)O(7) NBs could be promisingly utilized in the long-term course of photocatalysis. Furthermore, the result of performance evaluation under natural sunlight shows that the current Au-decorated Na(x)H(2-x)Ti(3)O(7) NBs can be used as highly efficient photocatalysts which may practically harvest energy from sunlight. (C) 2010 Elsevier B.V. All rights reserved.
Au-decorated NaxH2-xTi3O7 nanobelts exhibiting remarkable photocatalytic properties under visible-light illumination
(2010-06-18)
Pu, Ying-Chih
;
Chen, Yu-Chih
;
Hsu, Yung-Jung
;
材料科學與工程學系
;
Department of Materials Science and Engineering
We demonstrated for the first time that Na-intercalated H2Ti3O7 (NaxH2-xTi3O7) NBs, prepared in the typical alkaline hydrothermal process, can effectively absorb visible light to carry out photocatalytic reactions. With the capability of effective light absorption in visible range, NaxH2-xTi3O7 NBs performed much better in the photoclegradation of thionine than the other three counterpart products including H2Ti3O7, mixed Na2Ti6O13/TiO2 and anatase TiO2 under visible-light irradiations. As compared to the relevant commercial products like P-25 TiO2 and Na2Ti3O7 powders, the as-synthesized NaxH2-xTi3O7 NBs exhibited superior photocatalytic efficiency under UV illumination, demonstrating their potential as an efficient photocatalyst in relevant redox reactions. A further enhancement in the photocatalytic activity can be achieved for NaxH2-xTi3O7 NBs when Au nanoparticles of suitable amount were deposited on their surfaces. This improvement is due to the band offsets between NaxH2-xTi3O7 and Au, which may promote charge carrier separation to favor the photocatalysis. The recycling test reveals that Au-decorated NaxH2-xTi3O7 NBs could be promisingly utilized in the long-term course of photocatalysis. Furthermore, the result of performance evaluation under natural sunlight shows that the current Au-decorated NaxH2-xTi3O7 NBs can be used as highly efficient photocatalysts which may practically harvest energy from sunlight. (C) 2010 Elsevier B.V. All rights reserved.
Au/ZnS core/shell nanocrystals as an efficient anode photocatalyst in direct methanol fuel cells
(2013)
Chen, Wei-Ta
;
Lin, Yin-Kai
;
Yang, Ting-Ting
;
Pu, Ying-Chih
;
Hsu, Yung-Jung
Au/ZnS core/shell nanocrystals with controllable shell thicknesses were synthesized using a cysteine-assisted hydrothermal method. Incorporating Au/ZnS nanocrystals into the traditional Pt-catalyzed half-cell reaction led to a 43.3% increase in methanol oxidation current under light illumination, demonstrating their promising potential for metal/semiconductor hybrid nanocrystals as the anode photocatalyst in direct methanol fuel cells.
Au@Cu2O core@shell nanocrystals as dual-functional catalysts for sustainable environmental applications
(2019-03-01)
Kuo, Ming-Yu
;
Hsiao, Chih-Feng
;
Chiu, Yi-Hsuan
;
Lai, Ting-Hsuan
;
Fang, Mei-Jing
This work reports the synthesis of Au@Cu2O core@shell nanocrystals with controllable shell thicknesses and demonstrates their use as the dual-functional catalyst that can continuously operate under illumination and darkness conditions for efficient E. con inactivation. On account of the peroxidase mimics of the Au core and Fenton reactivity of the Cu2O shell, the Au@Cu2O nanocrystals exhibit intrinsic peroxidase-like property with the reaction kinetics in accordance with the typical Michaelis-Menten mechanism. On the other hand, time resolved photoluminescence spectra suggest the prevalence of pronounced charge separation for Au@Cu2O nanocrystals, an important advantage that is favourable for photocatalysis. By combining the photocatalytic capability with the peroxidase mimics features, Au@Cu2O nanocrystals can perform practical photocatalytic decomposition of E. coil under visible light illumination but still show vital activity towards E. coil inactivation after light illumination was turned off. The current study delivers a new catalyst configuration by exploiting the multiple functionalities of nanosized Au and Cu2O for advanced environmental and energy conversion applications.
Au@Cu7S4 yolk@shell nanocrystal-decorated TiO2 nanowires as an all-day-active photocatalyst for environmental purification
(2017-01)
Chiu, Yi-Hsuan
;
Hsu, Yung-Jung
;
材料科學與工程學系
;
Department of Materials Science and Engineering
A vital issue that degrades the entirety of photocatalysis on TiO2 is the requisite of light illumination for performing redox reactions. The ability to maintain the catalytic activity in dark environment has been the ultimate goal for the widespread deployment of TiO2 photocatalysts. Here, for the first time we reported the demonstration of an all-day-active photocatalyst model by employing Au@Cu7S4 yolk@shell nanocrystaldecorated TiO2 nanowires. The samples were obtained by depositing a Cu2O layer on the Au surface of Au particle-decorated TiO2 nanowires, followed by the sulfidation treatment on Cu2O layer to grow hollow Cu7S4 shell. By coupling the pronounced charge separation and distinctive peroxidase mimic properties from the constituents, the TiO2 -Au@Cu7S4 nanowires were capable of performing efficient methyl orange degradation under light illumination, 7yet still persisted noticeable activity of decomposing methyl orange after light irradiation was switched off. The present study has embodied a conceptually valuable design of permanently working photocatalysts, which may serve as a versatile platform for the widely distributed environmental and energy applications such as pollutant destruction and organic transformation.
Au@Cu7S4 yolk@shell nanocrystal-decorated TiO2 nanowires as an all-day-active photocatalyst for environmental purification
(2017-01)
Chiu, Yi-Hsuan
;
Hsu, Yung-Jung
;
材料科學與工程學系
;
Department of Materials Science and Engineering
A vital issue that degrades the entirety of photocatalysis on TiO2 is the requisite of light illumination for performing redox reactions. The ability to maintain the catalytic activity in dark environment has been the ultimate goal for the widespread deployment of TiO2 photocatalysts. Here, for the first time we reported the demonstration of an all-day-active photocatalyst model by employing Au@Cu7S4 yolk@shell nanocrystaldecorated TiO2 nanowires. The samples were obtained by depositing a Cu2O layer on the Au surface of Au particle-decorated TiO2 nanowires, followed by the sulfidation treatment on Cu2O layer to grow hollow Cu7S4 shell. By coupling the pronounced charge separation and distinctive peroxidase mimic properties from the constituents, the TiO2 -Au@Cu7S4 nanowires were capable of performing efficient methyl orange degradation under light illumination, 7yet still persisted noticeable activity of decomposing methyl orange after light irradiation was switched off. The present study has embodied a conceptually valuable design of permanently working photocatalysts, which may serve as a versatile platform for the widely distributed environmental and energy applications such as pollutant destruction and organic transformation.
Cathodic deposition of TiO2 thin films with supercritical CO2 emulsified electrolyte
(2013-08-01)
Chang, Tso-Fu Mark
;
Lin, Wei-Hao
;
Hsu, Yung-Jung
;
Chen, Chun-Yi
;
Sato, Tatsuo
TiO2 thin films were fabricated by cathodic deposition with a supercritical CO2 (sc-CO2) emulsified TiCl3 + NaNO3 electrolyte. Morphology and average grain size were evaluated by SEM, TEM and XRD. SEM micrographs showed that the TiO2 films fabricated by TiCl3 + NaNO3 electrolyte were porous, and the films were composed of particles and aggregates of the particles. Also, size of the particles increased when the sc-CO2 emulsified electrolyte was used. Average grain size of the TiO2 films was calculated using Scherrer equation. The average grain size was found to increase when the sc-CO2 emulsified electrolyte was used. In addition, both particle sizes observed from SEM and average grain size calculated using Scherrer equation were found to increase when pressure was increased from atmospheric pressure to 20 MPa. (c) 2013 Elsevier B.V. All rights reserved.
CdS/CdSe co-sensitized brookite H:TiO2 nanostructures: Charge carrier dynamics and photoelectrochemical hydrogen generation
(2018-06-05)
Chang, Yung-Shan
;
Choi, Mingi
;
Baek, Minki
;
Hsieh, Ping-Yen
;
Yong, Kijung
In this study, we have synthesized CdS/CdSe co-sensitized brookite TiO2 nanostructures with hydrogen doping (H:TiO2/CdS/CdSe) in a facile solution reaction and studied their PEC performances. Compared to undoped brookite TiO2, the H:TiO2/CdS/CdSe composites exhibit much enhanced photocurrent generation, which originates from the improved charge transfer kinetics endowed by hydrogen doping and sensitization. Time-resolved photoluminescence (PL) and electrochemical impendence spectroscopy (EIS) are employed to explore the charge transfer dynamics between sensitizers and TiO2 and charge carrier kinetics at the semiconductor/electrolyte interface. According to the analytical results, sensitizations of TiO2 are found to enhance the charge separation efficiency. Besides, the hydrogen doping into TiO2 generates oxygen vacancy states, providing additional charge transfer pathway and prohibiting charge recombination, beneficial for enhancing the PEC performances as well. Based on the charge dynamics data, we further develop charge transfer models for TiO2/CdS/CdSe and H:TiO2/CdS/CdSe. The findings from this work can help understanding the charge transfer dynamics in brookite TiO(2)based composite systems as well as designing versatile photoelectrodes for solar energy conversion.