Won-Chun Oh

Synthesis, characterization, and photocatalytic analysis of CNT/TiO2 composites derived from MWCNTs and titanium sources

Abstract CNT/TiO 2 composites were prepared using multi-walled carbon nanotubes (MWCNTs) as a starting material, and titanium(IV) isopropoxide, titanium(IV) propoxide and titanium(IV) n -butoxide as titanium sources and benzene as a solvent. The composites were characterized by N 2 adsorption, scanning electron microscopy, X-ray diffraction, energy dispersive X-ray analysis, and UV-vis absorption spectroscopy. The photoactivity of the prepared materials was evaluated by the conversion of methylene blue (MB, C 16 H 18 N 3 S·Cl·3H 2 O) in aqueous solution under UV irradiation. It can be found that the MB removal effect of the CNT/TiO 2 composites is not only due to the adsorption of MWCNTs and the photocatalytic degradation of TiO 2 but also to electron transfer between MWCNTs and TiO 2 .

Synthesis of fullerene modified with Ag2S with high photocatalytic activity under visible light

We improve the photocatalytic effect of Ag2S under visible light by using fullerene modified with Ag2S nanoparticles. Surface areas and pore volumes of the Ag2S–fullerene samples showed catastrophic decreases due to the deposition of Ag2S. The generation of reactive oxygen species was detected through the oxidation reaction from 1,5-diphenyl carbazide (DPCI) to 1,5-diphenyl carbazone (DPCO). It is found that the photocurrent density and the photocatalytic effect increase in the case with the modified fullerene. In comparison with the separate effects of Ag2S and fullerene nanoparticles, the photocatalytic effect of the fullerene modified with Ag2S composites is increased significantly due to the synergetic effect between the fullerene and the Ag2S nanoparticles.

The characteristic study and sonocatalytic performance of CdSe–graphene as catalyst in the degradation of azo dyes in aqueous solution under dark conditions

The sonocatalytic degradation of azo dyes; methyl orange (MO) and rhodamine B (RhB) were studied catalyzed by cadmium selenide (CdSe)-graphene in dark ambiance. The CdSe-graphene composites were prepared by simple hydrothermal method. The characterizations of composites were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), specific surface area (BET) and with energy dispersive X-ray (EDX). The UV-spectroscopic analysis of the dyes was done by measuring the change in absorbance. The degradation of the organic dyes was calculated based on the decrease in concentration of the dyes with respect to regular time intervals. The rate coefficients for the sonocatalytic process were successfully established and the reusability tests were done to test the stability of the used catalysts.

Effect of Pt treated fullerene/TiO2 on the photocatalytic degradation of MO under visible light

Platinum treated fullerene/TiO2 composites (Pt-fullerene/TiO2) were prepared using a sol–gel method. The composite obtained was characterized by FT-IR, BET surface area measurements, X-ray diffraction, energy dispersive X-ray analysis, transmission electron microscopy (TEM) and UV-vis analysis. A methyl orange (MO) solution under visible light irradiation was used to determine the photocatalytic activity. Excellent photocatalytic degradation of a MO solution was observed using the Pt-TiO2, fullerene-TiO2 and Pt-fullerene/TiO2 composites under visible light. An increase in photocatalytic activity was observed and Pt-fullerene/TiO2 has the best photocatalytic activity, which may be attributable to increase of the photo-absorption effect by the fullerene and the cooperative effect of the Pt.

Preparation, characterization and photocatalytic behavior of WO3-fullerene/TiO2 catalysts under visible light

WO3-treated fullerene/TiO2 composites (WO3-fullerene/TiO2) were prepared using a sol-gel method. The composite obtained was characterized by BET surface area measurements, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, transmission electron microscopy, and UV-vis analysis. A methyl orange (MO) solution under visible light irradiation was used to determine the photocatalytic activity. Excellent photocatalytic degradation of a MO solution was observed using the WO3-fullerene, fullerene-TiO2, and WO3-fullerene/TiO2 composites under visible light. An increase in photocatalytic activity was observed, and WO3-fullerene/TiO2 has the best photocatalytic activity; it may attribute to the increase of the photo-absorption effect by the fullerene and the cooperative effect of the WO3.

Sonocatalytic degradation and catalytic activities for MB solution of Fe treated fullerene/TiO2 composite with different ultrasonic intensity

Fe-fullerene/TiO(2) composite catalysts were prepared with titanium (IV) n-butoxide (TNB) by a sol-gel method. The samples were characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM), specific surface area (BET), X-ray diffraction analysis (XRD) and energy dispersive X-ray spectroscopy (EDX). The catalytic activities were evaluated by the catalytic oxidation of methylene blue (MB) solution. XRD patterns of the composites showed that the Fe-fullerene/TiO(2) composite contained a typical single and clear anatase phase. The surface properties shown by SEM present a characterization of the texture on Fe-fullerene/TiO(2) composites and showed a homogenous composition in the particles for the titanium sources used. The EDX spectra for the elemental identification showed the presence of C and Ti with strong Fe peaks for the Fe-fullerene/TiO(2) composite. The degradation of MB solution by ultrasonic irradiation in the presence of Fe-fullerene/TiO(2) compounds was investigated in complete darkness. With the increase in the amount of Fe, the degradation rate of methylene blue solution also increased.

Characterization and relative sonocatalytic efficiencies of a new MWCNT and CdS modified TiO2 catalysts and their application in the sonocatalytic degradation of rhodamine B

TiO(2) nanoparticles modified with MWCNTs and CdS were synthesized by the sol-gel method followed by solvothermal treatment at low temperature. The chemical composition and surface structure of the CdS/CNT-TiO(2) composites were investigated by X-ray diffraction, specific surface area measurements, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and scanning electron microscopy. Then a series of sonocatalytic degradation experiments were carried out under ultrasonic irradiation in the presence of CNT/TiO(2) and the CdS/CNT-TiO(2) composites. It was found that RhB was quickly and effectively degraded under different ultrasonic conditions. As expected, the nanosized CdS/CNT-TiO(2) photocatalyst showed enhanced activity compared with the non CdS treated CNT/TiO(2) material in the sonocatalytic degradation of RhB. The sonocatalyst CCTb with 34.68% contents of Ti heat treated at 500 °C for 1h showed the highest sonocatalytic activity. The synergistic effect of the greater surface area and catalytic activities of the composite catalysts was examined in terms of their strong adsorption ability and interphase interaction by comparing the effects of different amounts of MWCNTs and CdS in the catalysts and their roles. The mechanism of sonocatalytic degradation over the CdS/CNT modified TiO(2) composites under different ultrasonic conditions was also discussed.

One-step hydrothermal fabrication of strongly coupled Co3O4 nanosheets–reduced graphene oxide for electrochemical capacitors

In the work, we developed a one-step synthetic strategy to prepare a strongly coupled Co3O4 nanosheets–reduced graphene oxide (Co3O4 NSs–rGO) hybrid, and further utilized it as a promising electroactive material for electrochemical capacitors (ECs). During the hydrothermal procedure, the GO was reduced and Co3O4 NSs were in situ grown on the rGO sheets simultaneously due to the electrostatic interaction between the Co2+ and GO sheets. Electrochemical characteristics indicated that the Co3O4 NSs–rGO hybrid with ∼7.2 wt% Co3O4 loading delivered a specific capacitance (SC) of 187 F g−1 at 1.2 A g−1. Furthermore, the SC degradation of the hybrid was ∼6 and 9% at constant current densities of 1.2 and 5 A g−1 after 1000 continuous charge–discharge cycles, demonstrating its desirable electrochemical stability. The synergetic effect of nanoscale size and good redox activity of the Co3O4 NSs combined with the high electronic conductivity of the rGO resulted in the enhanced electrochemical utilization at high rates. In addition, an activated carbon/Co3O4 NSs–rGO asymmetric EC was further fabricated, and exhibited a specific energy density of ∼13.4 W h kg−1, specific power density of ∼2166 W kg−1 and striking electrochemical stability with ∼11% SC degradation after 1000 cycles.

Sonocatalytic degradation of Rhodamine B in the presence of C60 and CdS coupled TiO2 particles.

CdS-TiO2 and CdS-C60/TiO2 were prepared using C60, cadmium acetate dehydrate [(CH3COO)2Cd·2H2O], sodium sulfide (Na2S·5H2O) and titanium (IV) n-butoxide by a sol-gel method. The prepared sonocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and transmission electron microscopy (TEM). A rhodamine B (RhB) solution under ultrasonic irradiation was used to determine the catalytic activity. Excellent catalytic degradation of an RhB solution was observed using the CdS-C60/TiO2 composites under ultrasonic irradiation. C60 coupled CdS-TiO2 can enhance the Brunauer-Emmett-Teller (BET) surface area and increase the decolorization rate for rhodamine B solution. The results also shows that increase the content of CdS can enhance the catalytic activity.

Photocatalytic Degradation of Methylene Blue by CNT/TiO 2 Composites Prepared from MWCNT and Titanium n-butoxide with Benzene

In this study, CNT/TiO₂ composites were prepared using surface modified Multiwall carbon nanotube (MWCNT) and titanium n-butoxide (TNB) with benzene. The composites were characterized by nitrogen adsorption isotherms, scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX), FT-IR spectra, and UV-vis absorption spectroscopy. The UV radiation induced photoactivity of the CNT/TiO₂ composites was tested using a fixed concentration of methylene blue (MB, C 16 H 18 N₃SㆍCl·3H2₂) in an aqueous solution. Finally, it can be considered that the MB removal effect of the CNT/TiO₂ composites is not only due to the adsorption effect of MWCNTand photocatalytic degradation of TiO₂, but also to electron transfer between MWCNT and TiO₂.