Browsing by Author "Wang, Tsai-Te"

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Effective hydrogenation of TiO2 photocatalysts with CH3OH for enhanced water splitting: A computational and X-ray study
(2019-09-15)
Wang, Tsai-Te
;
Raghunath, Putikam
;
Lin, Yu-Chang
;
Lin, Yan-Gu
;
Lin, Ming-Chan
We have investigated computationally and experimentally the efficacy of CH3OH treatment of anatase TiO2 nanoparticles (NPs) and compared the results obtained with H-2 as the hydrogenation source. The results indicate that TiO2 NPs heated at 300 degrees C in 120 Torr of CH3OH vapor is more effective than the samples heated under 800 Torr of H-2 at the same temperature. Ultraviolet-visible spectroscopy (UV-VIS), Photoluminescence spectroscopy (PL) and X-ray diffraction spectroscopy (XRD) were employed to study the optical property. The effect of temperature of hydrogenation has been systematically studied for NPs in the 200-450 degrees C range for both H-sources based on H-2 evolution, employing Xe lamp as the light source. The hydrogenated TiO2 NPs using H-2 and CH3OH have been analyzed by soft X-ray absorption near-edge structure analyses with and without Xe lamp irradiation in situ. The result indicates that CH3OH hydrogenation can induce a much stronger Ti-O interaction along direction d(z)(2) and increase the unoccupied DOS of Ti t(2g) states. This is why the CH3OH treated TiO2 exhibits a greater photo-activity. The crucial role of the hydrogenation using CH3OH was also investigated systematically and confirmed by quantum-chemical calculations with complementary synchrotron-based X-ray techniques. The results are consistent with the predicted barriers for the formation of H atoms on the TiO2 surface, 4-9 kcal/mol, considerably lower than that in the H-2 case, 48 kcal/mol.
KSCN-activation of hydrogenated NiO/TiO2 for enhanced photocatalytic hydrogen evolution
(2020-05-01)
Wang, Tsai-Te
;
Chiang, Chao-Lung
;
Lin, Yu-Chang
;
Srinivasadesikan, Venkatesan
;
Lin, Ming-Chang
It was investigated the efficiency of hydrogen production from NiO-loaded TiO2 treated by methanol hydrogenation and functionalized by SCN ligand (SCN-M:(NiO/TiO2)). The effects of a p-n junction created between NiO and TiO2 were demonstrated to enhance significantly the overall photocatalytic performance. The optical and microstructural properties of SCN-M:(NiO/TiO2) were studied with ultraviolet-visible spectra (UV-Vis), photoluminescence (PL), Raman spectra, X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS). The atomic and electronic configurations of SCN-M:(NiO/TiO2) were investigated with analysis of the X-ray absorption near-edge structure (XAS) in situ under irradiation with Xe lamp incorporating a filter (AM 1.5G). An effective quantum yield of 1.34% for hydrogen production was attained with SCN-M:(NiO/TiO2). Quantum-chemical calculations revealed a synergistic decrease of the band gap upon loading Ni, Ni-linked O-2 and anionic SCN-ligand binding. The optimal energy bandgap was decreased to 2.70 eV for (SCN/O-2)-3Ni@TiO2, which reasonably supported the enhancement of H-2 evolution.
Observation of Significant enhancement in the efficiency of a DSSC by InN nanoparticles over TiO(2)-nanoparticle films
(2011-06-24)
Wang, Tsai-Te
;
Raghunath, P.
;
Lu, Yun-Fang
;
Liu, Yu-Chang
;
Chiou, Chwei-Huawn
We have studied the effect of InN deposited over TiO(2) nanoparticle (NP) films on the performance of dye-sensitized solar cells (DSSCs) using N3 dye with I(-)/I(3)(-) electrolyte. A 10-20% increase in efficiency was observed for InN deposited, N3 sensitized 5-8.5 mu m thick TiO(2) films as compared to similar non-treated films. The deposition of InN was carried out in the temperature range of 573-723 K organometallic chemical vapor deposition (OMCVD). Spectral shifts and DFT calculations with a model anchoring group (R'COOH) both suggest binding of the N3 dye directly to both InN and the InN/TiO(2) sites. (C) 2011 Elsevier B.V. All rights reserved.
Observation of Significant enhancement in the efficiency of a DSSC by InN nanoparticles over TiO2-nanoparticle films
(2011-06-24)
Wang, Tsai-Te
;
Raghunath, P.
;
Lu, Yun-Fang
;
Liu, Yu-Chang
;
Chiou, Chwei-Huawn
We have studied the effect of InN deposited over TiO2 nanoparticle (NP) films on the performance of dye-sensitized solar cells (DSSCs) using N3 dye with I-/I-3(-) electrolyte. A 10-20% increase in efficiency was observed for InN deposited, N3 sensitized 5-8.5 mu m thick TiO2 films as compared to similar non-treated films. The deposition of InN was carried out in the temperature range of 573-723 K organometallic chemical vapor deposition (OMCVD). Spectral shifts and DFT calculations with a model anchoring group (R'COOH) both suggest binding of the N3 dye directly to both InN and the InN/TiO2 sites. (C) 2011 Elsevier B.V. All rights reserved.