• Korean Journal of Materials Research
• /
• v.22 no.10
• /
• pp.504-507
• /
• 2012

Synthesis of RGO (reduced graphene oxide)-CdS composite material was performed through CBD (chemical bath deposition) method in which graphene oxide served as the support and Cadmium Sulfate Hydrate as the starting material. Graphene-based semiconductor photocatalysts have attracted extensive attention due to their usefulness for environmental and energy applications. The band gap (2.4 eV) of CdS corresponds well with the spectrum of sunlight because the crystalline phase, size, morphology, specic surface area and defects, etc., of CdS can affect its photocatalytic activity. The specific surface structure (morphology) of the photocatalyst can be effective for the suppression of recombination between photogenerated electrons and holes. Graphene (GN) has unique properties such as a high value of Young's modulus, large theoretical specific surface area, excellent thermal conductivity, high mobility of charge carriers, and good optical transmittance. These excellent properties make GN an ideal building block in nanocomposites. It can act as an excellent electron-acceptor/transport material. Therefore, the morphology, structural characterization and crystal structure were observed using various analytical tools, such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. From this analysis, it is shown that CdS particles were well dispersed uniformly in the RGO sheet. Furthermore, the photocatalytic property of the resulting RGO-CdS composite is also discussed in relation to environmental applications such as the photocatalytic degradation of pollutants. It was found that the prepared RGO-CdS nanocomposites exhibited enhanced photocatalytic activity as compared with that of CdS nanoparticles. Therefore, better efficiency of photodegradation was found for water purification applications using RGO-CdS composite.

• Nano
• /
• v.13 no.11
• /
• pp.1850127.1-1850127.13
• /
• 2018

Bi metal deposited on $Bi_2MoO_6$ composite photocatalysts have been successfully synthesized via a simple reduction method at room temperature with using $NaBH_4$ as the reducing agent. The photocatalytic activity of the composite was evaluated by degradation of rhodamine B (RhB) and bisphenol A (BPA) solution under visible light. The rate constant of $Bi/Bi_2MoO_6$ composite to RhB is 10.8 times that of $Bi_2MoO_6$, and the degradation rate constant of BPA is 6.9 times of that of $Bi_2MoO_6$. Nitrogen absorption-desorption isotherm proved that the increase of specific surface area is one of the reasons for the improvement of photocatalytic degradation activity of $Bi/Bi_2MoO_6$ composites. The higher charge transfer efficiency of $Bi/Bi_2MoO_6$ is found through the characterization of the photocurrent and impedance, which are attributed to the surface plasmon resonance (SPR) effect produced by the introduction of the metal Bi monomer in the composite. Free radical capture experiments proved that cavitation is the main active species. Based on the above conclusions, a possible mechanism of photocatalytic degradation is proposed.

• Journal of the Korean Ceramic Society
• /
• v.47 no.2
• /
• pp.136-141
• /
• 2010

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.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.19 no.5
• /
• pp.268-276
• /
• 2009

In this study, activated carbon (AC) was treated with ferric ion by a sol-gel method. The compound (Fe-AC) was employed for the preparation of Fe-activated carbon/$TiO_2$, (Fe-AC/$TiO_2$) composites. The prepared Fe-AC/$TiO_2$ composites were characterized with surface properties, structural crystallinity, elemental identification and photocatalytic activity. The SEM results showed that ferric compounds and titanium dioxide were fixed onto the AC surfaces. The XRD results showed that Fe-AC/$TiO_2$ composites mostly contained anatase phase. EDX showed the presence of C, O, and Ti with Fe peaks in all samples. Its photocatalytic degradation effect was evaluated with the degradation behavior of the methylene blue (MB) solution. MB degradation could be attributed to the synergetic effects of adsorption, photo-degradation of $TiO_2$ and photo-Fenton of Fe component. The degradation rate for this photocatalysis was evaluated as a function of the concentration of the dye, the amount of $TiO_2$ and the pH. Photocataytic activity is good at activity pH.

• KIEAE Journal
• /
• v.4 no.2
• /
• pp.37-40
• /
• 2004

New visible photocatalyst(Nanovis$^{(R)}$) has been synthesized to overcome the barrier of limitation of UV light utilization of current $TiO_2$ photocatalyst. It was found that red shift of absorption spectrum to 550nm was achieved. Its physical properties were characterized by XRD, BET and TEM. It is also observed that Nanovis$^{(R)}$ has a photocatalytic activity for photodegradation of Trichloroethylene under visible light irradiation. V,VII group doped into substitutional sites of $TiO_2$ has proven to be indispensable for band-gap narrowing and photocatalytic activity. These test results lead us to conclude that Nanovis$^{(R)}$ can be used for IAQ improvemen and for photocatalytic water splitting to hydrogen.

• Bulletin of the Korean Chemical Society
• /
• v.22 no.12
• /
• pp.1371-1374
• /
• 2001

Metal doping was adopted to modify TiO2 (P-25) and enhance the photocatalytic degradation of harmful cyanides in aqueous solution. Ni, Cu, Co, and Ag doped TiO2 were found to be active photocatalysts for UV light induced degradation of aqueous cyanides generating cyanate, nitrate and ammonia as main nitrogen-containing products. The photoactivity of Ni doped TiO2 was greatly affected by the state of Ni, that is, the crystal size and the degree of reduction of Ni. The modification effects of some mixed oxides, that is, Ni-Cu/TiO2 were also studied. The activity of Ni-Cu/TiO2 for any ratio of Cu/Ni was higher than that of Ni- or Cu-doped TiO2, and the catalyst at the Cu/Ni ratio of 0.3 showed the highest activity for cyanide conversion.

• Advances in Energy Research
• /
• v.2 no.1
• /
• pp.33-45
• /
• 2014

Photocatalytic hydrogen generation by water splitting ($H_2O_{(1)}{\rightarrow}H_2_{(g)}+1/2O_2_{(g)}$) has been studied on photocatalysts based on Zn, Cd, Fe and Cu, synthesized by coprecipitation. Iron and copper nanoparticles were incorporated as cocatalysts to enhance the photocatalytic activity of the ZnCd solid solution. The effect of the different synthesis parameters (temperature, elemental atomic ratios, amount of Cu and Fe incorporated in the catalyst and calcination temperature) on the photocatalytic production of hydrogen has been studied in order to determine the best experimental synthesis conditions. The catalysts have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and BET. The experiments of photocatalytic water splitting were performed in aqueous solution of the photocatalysts previously dispersed in a soft ultrasound bath. The photocatalysts were irradiated under different lights ranging from 220 to 700 nm. The photocatalytic activity was found to be clearly dependent on the specific area of the photocatalyst.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.08a
• /
• pp.270.1-270.1
• /
• 2013

Zinc oxide (ZnO) is one of the most powerful materials for purifying organic pollutants using photocatalytic activity. In this study, we have introduced a novel method to design highly photoreactive flexible 3 dimensional (3D) ZnO nanocomposite [F-ZnO-m (m: reaction time, min)] by electrospinning and simple-step ZnO growth processing (one-step ZnO seed coating/growth processing). Significantly, the F-ZnO-m could be a new platform (or candidate) as a photocatalytic technology for both morphology control and largearea production. The highest photocatalytic degradation rate ([k]) was observed for F-ZnO-m at 2.552 h-1, which was 8.1 times higher than that of ZnO nanoparticles (NPs; [k] = 0.316 h-1). The enhanced photocatalytic activity of F-ZnO-m may be attributed to factors such as large surface area. The F-ZnO-m is highly recyclable and retained 98.6% of the initial decolorization rate after fifteen cycles. Interestingly, the F-ZnO-m samples show very strong antibacterial properties against both Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) after exposure to UV-light for 30 min. The antibacterial properties of F-ZnO-m samples are more effective than those of ZnO NPs. More than 96.6% of the E. coli is sterilized after ten cycles. These results indicate that F-ZnO-m samples might have utility in several promising applications such as highly efficient water/air treatment and inactivation of pathogenic microorganisms.

• Journal of the Korean Ceramic Society
• /
• v.48 no.4
• /
• pp.282-287
• /
• 2011

ACF and $WO_3$ modified $TiO_2$ composites (ACF/$WO_3$/$TiO_2$) were prepared using a sol-gel method. The composites were characterized by Brunauer.Emmett.Teller (BET) surface area measurements, X-ray diffraction (XRD), energy dispersive X-ray (EDX) analysis and scanning electron microscope (SEM) analysis. A methyl orange (MO) solution under visible light irradiation was used to determine the photocatalytic activity. The degradation of the MO was determined using UV/Vis spectrophotometry. An increase in photocatalytic activity was observed and attributed to an increase of the photo-absorption effect by the $WO_3$ and the cooperative effect of the ACF.

• Journal of the Korean Ceramic Society
• /
• v.48 no.5
• /
• pp.433-438
• /
• 2011

In this study, CdS combined activated carbon/$TiO_2$ (CdS-AC/$TiO_2$) composites were prepared by a sol-gel method to improve the photocatalytic performance of $TiO_2$. These composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and UV-vis analysis. The photocatalytic activities were examined by the degradation of methylene blue (MB) under visible light irradiation. The photodegradation rate of MB under visible light irradiation reached 90.1% in 120 min. The kinetics of MB degradation was plotted alongside the values calculated from the Langmuir-Hinshelwood equation. The 0.2 CAT sample showed the best photocatalytic activity, which might be due to an increase in the photo-absorption effect by activated carbon and the cooperative effect of CdS.