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Photo-Catalytic Properties of TiO2 Supported on MWCNTs, SBA-15 and Silica-Coated MWCNTs Nanocomposites.

Ramoraswi NO, Ndungu PG - Nanoscale Res Lett (2015)

Bottom Line: All supported titania composites had high surface areas (207-301 m(2)/g), altered band gap energies and reduced TiO2 crystallite sizes.In addition, an interesting observation was noted with the TiO2/SBA-15 nanocomposites, which had a significantly greater photo-catalytic activity than the TiO2/CNT nanocomposites in spite of the high electron-hole recombination phenomena observed with the photoluminescence results.Discussions in terms of morphological, textural and physical-chemical aspects to account for the result are presented.

View Article: PubMed Central - PubMed

Affiliation: School of Chemistry, University of KwaZulu-Natal, Westville Campus, Durban, South Africa.

ABSTRACT
Mesoporous silica, specifically SBA-15, acid-treated multi-walled carbon nanotubes and a hybrid nanocomposite of SBA-15 coated onto the sidewalls acid-treated multi-walled carbon nanotubes (CNTs) were prepared and used as supports for anatase TiO2. Sol-gel methods were adapted for the synthesis of selected supports and for coating the materials with selected wt% loading of titania. Physical and chemical properties of the supports and catalyst composite materials were investigated by powder X-ray diffraction (XRD), Raman spectroscopy, thermogravimetric analysis, scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), UV-vis diffuse reflectance spectroscopy and fluorescence spectroscopy. The photo-activity of the catalyst composites were evaluated on the decolorisation of methylene blue as a model pollutant. Coating CNTs with SBA-15 improved the thermal stability and textural properties of the nanotubes. All supported titania composites had high surface areas (207-301 m(2)/g), altered band gap energies and reduced TiO2 crystallite sizes. The TiO2/SBA-CNT composite showed enhanced photo-catalytic properties and activity than the TiO2/SBA-15 and TiO2/CNT composites. In addition, an interesting observation was noted with the TiO2/SBA-15 nanocomposites, which had a significantly greater photo-catalytic activity than the TiO2/CNT nanocomposites in spite of the high electron-hole recombination phenomena observed with the photoluminescence results. Discussions in terms of morphological, textural and physical-chemical aspects to account for the result are presented.

No MeSH data available.


Related in: MedlinePlus

Decolourization of MB in the presence of 30 W halogen lamp and the various TiO2 catalysts, sorption equilibrium properties of the materials (a) and the photo-catalytic activity (b)
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Fig8: Decolourization of MB in the presence of 30 W halogen lamp and the various TiO2 catalysts, sorption equilibrium properties of the materials (a) and the photo-catalytic activity (b)

Mentions: Figure 8a compares the decolorisation of MB by titania, P25, 10 wt% titania on CNTs, SBA-15 and SBA-15-CNT nanocomposite. The titania and P25 were ineffective with the low-power light source used, and only absorbed a minimal amount of dye in the dark, and then desorbed some dye on excitation by the light source, with eventually a small amount of the dye being degraded. The supported titania composites effectively absorbed a significant amount of the dye under dark conditions, and when normalising the concentration after absorption in the dark, these composites effectively degraded the dye, as shown in Fig. 8b. Prior work in the literature has shown that MB reaches an absorption-desorption equilibrium in the dark without undergoing any degradation on titania catalysts supported SBA-15 and CNT [12–16, 19, 24–27, 68]. The noteworthy comparison in Fig. 8a is that on illumination, there is a slight increase in MB with the homemade mesoporous titania sample and the P25, which indicates some desorption of MB before the minimal degradation. Whereas, the supported titania catalysts undergo a further drop on illumination, with no slight increase as observed with the P25 and mesoporous titania controls, indicating that the MB absorbed onto the surface of these supported catalysts undergoes degradation rapidly under illumination.Fig. 8


Photo-Catalytic Properties of TiO2 Supported on MWCNTs, SBA-15 and Silica-Coated MWCNTs Nanocomposites.

Ramoraswi NO, Ndungu PG - Nanoscale Res Lett (2015)

Decolourization of MB in the presence of 30 W halogen lamp and the various TiO2 catalysts, sorption equilibrium properties of the materials (a) and the photo-catalytic activity (b)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4627977&req=5

Fig8: Decolourization of MB in the presence of 30 W halogen lamp and the various TiO2 catalysts, sorption equilibrium properties of the materials (a) and the photo-catalytic activity (b)
Mentions: Figure 8a compares the decolorisation of MB by titania, P25, 10 wt% titania on CNTs, SBA-15 and SBA-15-CNT nanocomposite. The titania and P25 were ineffective with the low-power light source used, and only absorbed a minimal amount of dye in the dark, and then desorbed some dye on excitation by the light source, with eventually a small amount of the dye being degraded. The supported titania composites effectively absorbed a significant amount of the dye under dark conditions, and when normalising the concentration after absorption in the dark, these composites effectively degraded the dye, as shown in Fig. 8b. Prior work in the literature has shown that MB reaches an absorption-desorption equilibrium in the dark without undergoing any degradation on titania catalysts supported SBA-15 and CNT [12–16, 19, 24–27, 68]. The noteworthy comparison in Fig. 8a is that on illumination, there is a slight increase in MB with the homemade mesoporous titania sample and the P25, which indicates some desorption of MB before the minimal degradation. Whereas, the supported titania catalysts undergo a further drop on illumination, with no slight increase as observed with the P25 and mesoporous titania controls, indicating that the MB absorbed onto the surface of these supported catalysts undergoes degradation rapidly under illumination.Fig. 8

Bottom Line: All supported titania composites had high surface areas (207-301 m(2)/g), altered band gap energies and reduced TiO2 crystallite sizes.In addition, an interesting observation was noted with the TiO2/SBA-15 nanocomposites, which had a significantly greater photo-catalytic activity than the TiO2/CNT nanocomposites in spite of the high electron-hole recombination phenomena observed with the photoluminescence results.Discussions in terms of morphological, textural and physical-chemical aspects to account for the result are presented.

View Article: PubMed Central - PubMed

Affiliation: School of Chemistry, University of KwaZulu-Natal, Westville Campus, Durban, South Africa.

ABSTRACT
Mesoporous silica, specifically SBA-15, acid-treated multi-walled carbon nanotubes and a hybrid nanocomposite of SBA-15 coated onto the sidewalls acid-treated multi-walled carbon nanotubes (CNTs) were prepared and used as supports for anatase TiO2. Sol-gel methods were adapted for the synthesis of selected supports and for coating the materials with selected wt% loading of titania. Physical and chemical properties of the supports and catalyst composite materials were investigated by powder X-ray diffraction (XRD), Raman spectroscopy, thermogravimetric analysis, scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), UV-vis diffuse reflectance spectroscopy and fluorescence spectroscopy. The photo-activity of the catalyst composites were evaluated on the decolorisation of methylene blue as a model pollutant. Coating CNTs with SBA-15 improved the thermal stability and textural properties of the nanotubes. All supported titania composites had high surface areas (207-301 m(2)/g), altered band gap energies and reduced TiO2 crystallite sizes. The TiO2/SBA-CNT composite showed enhanced photo-catalytic properties and activity than the TiO2/SBA-15 and TiO2/CNT composites. In addition, an interesting observation was noted with the TiO2/SBA-15 nanocomposites, which had a significantly greater photo-catalytic activity than the TiO2/CNT nanocomposites in spite of the high electron-hole recombination phenomena observed with the photoluminescence results. Discussions in terms of morphological, textural and physical-chemical aspects to account for the result are presented.

No MeSH data available.


Related in: MedlinePlus