Browsing by Author "Lin, Y. G."

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Effect of Fe2O3 coating on ZnO nanowires in photoelectrochemical water splitting: A synchrotron x-ray spectroscopic and spectromicroscopic investigation
(2020-06-01)
Lu, Y. R.
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Wang, Y. F.
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Chang, H. W.
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Huang, Y. C.
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Chen, J. L.
An array of ZnO/Fe2O3 core-shell nanowires (NW) for the highly efficient absorption of light and carrier collection is developed for use in photoelectrochemical (PEC) water-splitting. The oriented NW architecture favors physical matching, providing a direct electron conduction pathway and reducing the diffusion length of photogenerated holes. This work involves a combination of spectral imaging, spectromicroscopy and in situ x-ray absorption spectroscopy; spectra are obtained under operando conditions. Direct investigation of oriented nanowires using polarization-dependent x-ray spectromicroscopy enables the determination of the relationship between anisotropic electronic orbitals and charge carrier water-splitting efficiency. The results of O K-edge STXM demonstrated that the ZnO/Fe2O3 core-shell NW exhibits strong anisotropy and thus provides higher electron-hole transport efficiency than bare ZnO. In situ XAS revealed that interfacial charge transfer between Fe 3d and Zn 4p states enhances the photoelectrochemical reaction in the ZnO/Fe2O3 core-shell NW. The photogenerated electrons of Fe2O3 are transferred from Fe 3d states to the Zn 4p state under photoelectrochemical conditions.
Effects of nitrogen-doping on the microstructure, bonding and electrochemical activity of carbon nanotubes
(2009-02-01)
Lin, Y. G.
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Hsu, Y. K.
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Wu, C. T.
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Chen, S. Y.
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Chen, K. H.
Vertically aligned carbon nanotubes produced with in-situ doping of nitrogen (CN(x) NTs) during chemical vapor deposition exhibit unique structural and electrochemical properties, which are strongly correlated with their nitrogen (N) doping level. In this work, the effects of N-doping on CN(x) NTs have been systematically investigated via microstructure and bonding studies, electron-transfer (ET) behaviors, and subsequent electrochemical deposition of catalyst. The CN(x) NTs doped with an optimal N level, while showing a nearly reversible ET behavior, in fact exhibit uniform and high density of surface defects. These surface defects are desirable for further modification and/or nucleation of catalytic particles on the surface of CN(x) NTs to form a composite electrode for electrochemical energy device applications such as fuel cells and capacitors. (c) 2008 Elsevier B.V. All rights reserved.
Synergistic Effect of Hydrogenation and Thiocyanate Treatments on Ag-Loaded TiO2 Nanoparticles for Solar-to-Hydrogen Conversion
(2017-05-11)
Wang, T. T.
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Raghunath, P.
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Lin, Y. G.
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Lin, M. C.
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應用化學系分子科學碩博班
H-2 evolution rate enhanced by Ag-loading on 25 nm TiO2 anatase nanopatticles (denoted as Ag/TiO2), Ag-loaded on hydrogenated TiO2 NPs (Ag/H:TiO2), as well as by the treatment of both NPs with potassium thiocyanate (KSCN) solution have been systematically investigated in conjunction with quantum-chemical-calculations and XANES and EXAFS analyses with synchrotron radiation. We have observed a cumulative enhancement effect of these fabrication processes on solar to;hydrogen A To(STH) conversion using a. simulating light source, Ag/TiO2 shows an enhanced visible absorption with 4-5 tiine increase in H-2 evolutioh over that of TiO2 or H:TiO2 prepared under mild hydrogenation conditions, while Ag/H:TiO2 exhibits an even greater UV visible absorption, similar to that of Ag/H:TiO2 with 3.1 times higher STH than that of Ag/TiO2. The treatment of Ag/TiO2 and Ag/H:TiO2 NPs With 0.1 mM KSCN solution, further increases:their STHs by 3.6 and 2.8 times, respectively. Optimization of KSCN concentration up to 02 mM gave [H-2] production rate rise to 2.75 mmol h(-1) g(-1) under Xe lamp illumination for the AgSCN/H:TiO2 system, which has also been tested for its durability, showing a notable robustness. The observed synergistic effect of TiO2 hydrogenation and SCN treatment of the Ag/H:TiO2 NPs has been corroborated by the results of quantum chemical elucidation of H2 production mechanism and the photocatalytic effects of Ag/H:TiO2 and AgSCN/H:TiO2 NPs revealed by appearances of new sub-band states within the TiO2 bandgap, as well as by the result of XANES and EXAFS analyses which support the electron pulling effect of the SCN group attached to Ag. Finally, we have also compared the efficacies of H-2, HCOOH, and CH3OH as hydrogenation sources at 300 degrees C and the efficacies of CH3OH, C2H5OH, and sucrose as sacrificial agent to facilitate the separation of the electron from the hole.