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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

UV-vis diffuse reflectance measurements on P25 and mesoporous titania (a) and the corresponding plot of (αhν)2 vs. hν (b). c UV-vis diffuse reflectance measurements on titania supported on SBA-15, CNTs and SBA-CNT, with d showing the corresponding plots of (αhν)2 vs. hν
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Fig6: UV-vis diffuse reflectance measurements on P25 and mesoporous titania (a) and the corresponding plot of (αhν)2 vs. hν (b). c UV-vis diffuse reflectance measurements on titania supported on SBA-15, CNTs and SBA-CNT, with d showing the corresponding plots of (αhν)2 vs. hν

Mentions: UV-vis diffuse reflectance measurements and the corresponding plots of (αhν)2 vs. hν of the titania and supported titania samples are presented in Fig. 6a–d, respectively. All of the materials had intense absorptions in the UV-vis range, with a noticeable red shift with the ordered mesoporous titania samples. The band gap can be estimated from the plots of (αhν)2 vs. hν [18, 50, 58, 59], and the estimated band gap energies were 3.18, 3.34 and 3.42 eV for mesoporous the mesoporous titania, P25 sample and the titania supported on SBA-15, respectively. The titania supported on CNTs and SBA-CNT nanocomposites had an extended absorption feature well into the visible end of the spectrum and the corresponding plots of (αhν)2 vs. hν had a continuous energy feature which may indicate excitations at low band gap energies. The red shift indicates a decrease in band gap energy and that these materials are active in the visible region of the electromagnetic spectrum.Fig. 6


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

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

UV-vis diffuse reflectance measurements on P25 and mesoporous titania (a) and the corresponding plot of (αhν)2 vs. hν (b). c UV-vis diffuse reflectance measurements on titania supported on SBA-15, CNTs and SBA-CNT, with d showing the corresponding plots of (αhν)2 vs. hν
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig6: UV-vis diffuse reflectance measurements on P25 and mesoporous titania (a) and the corresponding plot of (αhν)2 vs. hν (b). c UV-vis diffuse reflectance measurements on titania supported on SBA-15, CNTs and SBA-CNT, with d showing the corresponding plots of (αhν)2 vs. hν
Mentions: UV-vis diffuse reflectance measurements and the corresponding plots of (αhν)2 vs. hν of the titania and supported titania samples are presented in Fig. 6a–d, respectively. All of the materials had intense absorptions in the UV-vis range, with a noticeable red shift with the ordered mesoporous titania samples. The band gap can be estimated from the plots of (αhν)2 vs. hν [18, 50, 58, 59], and the estimated band gap energies were 3.18, 3.34 and 3.42 eV for mesoporous the mesoporous titania, P25 sample and the titania supported on SBA-15, respectively. The titania supported on CNTs and SBA-CNT nanocomposites had an extended absorption feature well into the visible end of the spectrum and the corresponding plots of (αhν)2 vs. hν had a continuous energy feature which may indicate excitations at low band gap energies. The red shift indicates a decrease in band gap energy and that these materials are active in the visible region of the electromagnetic spectrum.Fig. 6

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