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RISS 인기검색어
- 검색키워드
- 저자 : Kan Zhang (검색결과 135 건)
- 무료
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Zhang, Kan,Oh, Won-Chun The Korean Ceramic Society 2010 한국세라믹학회지 Vol.47 No.2
ACF/ZnO photocatalyst was synthesized by a sol-gel method using activated carbon fiber (ACF) and Zn $(NO_3)_2$ as precursors. Samples were characterized by Brunauer-Emmett-Teller measurements (BET), scanning electron microscope (SEM), X-ray diffraction (XRD), and energy dispersive X-ray (EDX). The XRD results showed that ACF/ZnO composites only included a hexagonal phase by heat-treated temperature at $400^{\circ}C$, $500^{\circ}C$, $600^{\circ}C$, and $700^{\circ}C$. The SEM analysis revealed that the ACF/ZnO composites did not exhibit any morphological changes of the catalyst surface according to the different heat-treated temperatures. The photocatalytic activity of the samples was tested for degradation of methylene blue (MB) solutions under ultraviolet (UV) light and ultrasonication respectively. The results showed that the photocatalytic activity of ACF/ZnO composites heat-treated at $500^{\circ}C$ was higher than other samples, which is ascribed to the fine distribution of ZnO particles on the surface of the ACF. In addition, an ultrasound of low power (50 W) was used as an irradiation source to successfully induce ACF/ZnO composites to perform sonocatalytic degradation of MB. Results indicated that the sonocatalytic method in the presence of ACF/ZnO composites is an advisable choice for the treatments of organic dyes.
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Photodegradation of MB on Fe/CNT-TiO<sub>2</sub> Composite Photocatalysts Under Visible Light
Zhang, Kan,Meng, Ze-Da,Choi, Jong-Geun,Oh, Won-Chun Materials Research Society of Korea 2010 한국재료학회지 Vol.20 No.5
The composite photocatalysts of a Fe-modified carbon nanotube (CNT)-$TiO_2$ were synthesized by a two-step sol-gel method at high temperature. Its chemical composition and surface properties were investigated by BET surface area, scanning electron microscope (SEM), Transmission Electron Microscope (TEM), X-ray diffraction (XRD) and ultraviolet-visible (UV-Vis) spectroscopy. The results showed that the BET surface area was improved by modification of Fe, which was related to the adsorption capacity for each composite. Interesting thin layer aggregates of nanosized $TiO_2$ were observed from TEM images, probably stabilized by the presence of CNT, and the surface and structural characterization of the samples was carried out. The XRD results showed that the Fe/CNT-$TiO_2$ composites contained a mix of anatase and rutile forms of $TiO_2$ particles when the precursor is $TiOSO_4{\cdot}xH_2O$ (TOS). An excellent photocatalytic activity of Fe/CNT-$TiO_2$ was obtained for the degradation of methylene blue (MB) under visible light irradiation. It was considered that Fe cation could be doped into the matrix of $TiO_2$, which could hinder the recombination rate of the excited electrons/holes. The photocatalytic activity of the composites was also found to depend on the presence of CNT. The synergistic effects among the Fe, CNT and $TiO_2$ components were responsible for improving the visible light photocatalytic activity.
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Kan Zhang,오원춘 한국세라믹학회 2010 한국세라믹학회지 Vol.47 No.2
ACF/ZnO photocatalyst was synthesized by a sol-gel method using activated carbon fiber (ACF) and Zn (NO3)2 as precursors. Samples were characterized by Brunauer-Emmett-Teller measurements (BET), scanning electron microscope (SEM), X-ray diffraction (XRD), and energy dispersive X-ray (EDX). The XRD results showed that ACF/ZnO composites only included a hexagonal phase by heat-treated temperature at 400oC, 500oC, 600oC, and 700oC. The SEM analysis revealed that the ACF/ZnO composites did not exhibit any morphological changes of the catalyst surface according to the different heat-treated temperatures. The photocatalytic activity of the samples was tested for degradation of methylene blue (MB) solutions under ultraviolet (UV) light and ultrasonication respectively. The results showed that the photocatalytic activity of ACF/ZnO composites heat-treated at 500oC was higher than other samples, which is ascribed to the fine distribution of ZnO particles on the surface of the ACF. In addition, an ultrasound of low power (50 W) was used as an irradiation source to successfully induce ACF/ZnO composites to perform sonocatalytic degradation of MB. Results indicated that the sonocatalytic method in the presence of ACF/ZnO composites is an advisable choice for the treatments of organic dyes.
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Photodecomposition of Different Organic Dyes Using Fe-CNT/TiO2 Composites under UV and Visible Light
Kan Zhang,Ze-Da Meng,오원춘 한국세라믹학회 2010 한국세라믹학회지 Vol.47 No.2
The Fe-treated CNT/TiO2 photocatalysts mixed with anatase and rutile phase have been developed for the decomposition of non-biodegradable different organic dyes like methylene blue (MB), rhodamine B (Rh.B), and methyl orange (MO) in two conditions as ultraviolet and visible light respectively. The results indicate that all the Fe-CNT/TiO2 composites proved to be more efficient photocatalysts since degradation of MB at higher reaction rates, tthe decomposition rate of different dyes increases with an increase of Fe3+ concentration in composites the highest rate of decomposition of different dyes was noted under UV irradiation. These results can indicate that the large CNT network is facilitate the electron transfer and strongly adsorb dye molecules on the texted photocatalysts, iron is reactive in the photo-Fenton process resulting in high production of OH radicals and also high activity of the photocatalyst. And Fe particles can generate more photoinduced electrons to conduction band of TiO2 under visible light irradiation. The composites of Fe-CNT/TiO2 photocatalysts synthesized by a sol-gel method were characterized by BET, TEM, SEM, XRD and EDX.
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Kan Zhang,Won-Chun Oh 한국세라믹학회 2009 한국세라믹학회지 Vol.46 No.6
The Fe-ACF/TiO₂ composites were prepared by a sol-gel method and were characterized by nitrogen adsorption, Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and Energy Dispersive X-ray (EDX). The Fe-CF/TiO₂ composites were developed for the decomposition of organic dyes by using a UV lamp. The decomposition effect was investigated under various conditions, such as three selected non-biodegradable organic dyes like Methylene Blue (MB), Methyl Orange (MO), Rhodamine B (Rh.B), and in the presence of Fe and hydrogen peroxide (H₂O₂). The photocatalytic activity was derived from possible combination effects, such as (1) adsorption of ACF, (2) generation of electron/hole by TiO₂, (3) photo-nton reaction of Fe, and (4) oxidation of Fe2+ to Fe3+ by H₂O₂.
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Zhang, Kan,Oh, Won-Chun Materials Research Society of Korea 2010 한국재료학회지 Vol.20 No.1
Methylene blue (MB) was degraded by $TiO_2$ and ZnO deposited on an activated carbon fiber (ACF) surface under UV light. The ACF/$TiO_2$ and ACF/ZnO composites were characterized by BET, SEM, XRD, and EDX. The BET surface area was related to the adsorption capacity for composites. The SEM results showed that titanium dioxide and zinc oxide are distributed on the ACF surface. The XRD results showed that the ACF/$TiO_2$ and ACF/ZnO composites contained a unique anatase structure for $TiO_2$ and a typical hexagonal phase for ZnO respectively. These EDX spectra showed the presence of peaks of Ti element on ACF/$TiO_2$ composite and peaks of Zn element on the ACF/ZnO composite. The blank experiments for either illuminating the MB solution or the suspension containing ACF/$TiO_2$ or ACF/ZnO in the dark showed that both illumination and the catalyst were necessary for the mineralization of organic dye. Additionally, the ACF/$TiO_2$ composites proved to be efficient photocatalysts due to degradation of MB at higher reaction rates. The addition of an oxidant $([NH_4]_2S_2O_8)$ led to an increase of the degradation rate of MB for ACF/$TiO_2$ and ACF/ZnO composites.
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Photoelectrochemical cells with tungsten trioxide/Mo-doped BiVO<sub>4</sub> bilayers
Zhang, Kan,Shi, Xin-Jian,Kim, Jung Kyu,Park, Jong Hyeok The Royal Society of Chemistry 2012 Physical chemistry chemical physics Vol.14 No.31
<P>Mo-doped BiVO<SUB>4</SUB> nanocrystals with low bandgap energy were embedded into the surface of WO<SUB>3</SUB> film, resulting in WO<SUB>3</SUB>/BiV<SUB>0.95</SUB>Mo<SUB>0.05</SUB>O<SUB>4</SUB> photoanodes, which were tested in photoelectrochemical cells for water splitting. Bilayer photoelectrochemical cells showed enhanced photocurrent density: three times that shown by a cell with a pure WO<SUB>3</SUB> photoanode and 1.5 times that of a cell with a WO<SUB>3</SUB>/BiVO<SUB>4</SUB> bilayer photoanode. BiVO<SUB>4</SUB> showed poor charge carrier mobility; the performance of photoelectrochemical cells can be improved only when BiVO<SUB>4</SUB> is combined with a WO<SUB>3</SUB> bottom layer, even after Mo doping and tailoring its transition energies by atomic doping.</P> <P>Graphic Abstract</P><P>High photocurrent density was achieved by WO<SUB>3</SUB>/Mo-doped BiVO<SUB>4</SUB> (BiV<SUB>0.95</SUB>Mo<SUB>0.05</SUB>O<SUB>4</SUB>) bilayers in which the Mo atoms increased charge generation, resulting in improved photocurrent density. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2cp40991g'> </P>
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Zhang, Kan,Heo, Nansra,Shi, Xinjian,Park, Jong Hyeok American Chemical Society 2013 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.117 No.45
<P>We report a simple and versatile strategy for hybridizing 1-D silver trimolybdate wires (Ag<SUB>2</SUB>Mo<SUB>3</SUB>O<SUB>10</SUB> Ws) and graphene oxide (GO) by a direct solution process. Because of the photoactive nature of Ag<SUB>2</SUB>Mo<SUB>3</SUB>O<SUB>10</SUB> Ws, Ag particles were uniformly formed on their surfaces with the assistance of solar light. Enriched surface functional groups of GO from chemical activation induce a chemical coordination with these Ag particles. As a result, a uniform ternary hybrid mixture was successfully formed with metallic Ag nanoparticles as a bridge connecting activated GO and Ag<SUB>2</SUB>Mo<SUB>3</SUB>O<SUB>10</SUB> Ws. We found that both excited GO and Ag<SUB>2</SUB>Mo<SUB>3</SUB>O<SUB>10</SUB> could generate electron/hole pairs separated in space by metallic Ag as a solid-state electron mediator. The novel photocatalytic mechanism was confirmed using photocurrents, the electronic-band structure, and photoactivity correlation analysis.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2013/jpccck.2013.117.issue-45/jp407038c/production/images/medium/jp-2013-07038c_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp407038c'>ACS Electronic Supporting Info</A></P>
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Zhang, Feng-Jun,Chen, Ming-Liang,Zhang, Kan,Oh, Won-Chun Korean Chemical Society 2010 Bulletin of the Korean Chemical Society Vol.31 No.1
Photoelectrocatalytic decolorization of methlene blue (MB) in the presence of two types of carbon nanotube/titania and yttrium-treated carbon nanotube/titania electrodes in aqueous solutions were studied under visible light. The prepared composite electrodes were characterized by X-ray diffraction, transmission and scanning electron microscopy, energy dispersive X-ray analysis, and photoelectrocatalytic activity. The photoelectrocatalytic performances of the supported catalysts were evaluated for the decolorization of MB solution under visible light irradiation. The results showed that yttrium incorporation enhanced the decolorization rate of MB. It was found that the photoelectrocatalytic degradation of a MB solution could be attributed to the combined effects caused by the photo-degradation of titania, the electron assistance of carbon nanotube network, the enhancement of yttrium and a function of the applied potential. The repeatability of photocatalytic activity was also tested. The presence of yttrium enhanced the hydrophillicity of yttrium-carbon nanotubes/titania electrode because more OH groups can be adsorbed on the surface.
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