Limits...
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

a The XRD pattern of raw and acid-treated CNTs. b The wide-angle XRD pattern for SBA-15 samples. c The low-angle XRD pattern for SBA-15. d The wide-angle XRD pattern for various wt% loadings of SBA-15 coated on CNTs
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4627977&req=5

Fig1: a The XRD pattern of raw and acid-treated CNTs. b The wide-angle XRD pattern for SBA-15 samples. c The low-angle XRD pattern for SBA-15. d The wide-angle XRD pattern for various wt% loadings of SBA-15 coated on CNTs

Mentions: Figure 1a depicts the XRD patterns of the pristine and acid-treated CNT structures. The characteristic peaks of the CNTs appear at 2θ values of 26.00° and 43.40°. The strong and sharp diffraction peak at 2θ = 25.70 was indexed to the (002) reflection of graphite [30]. The relative sharpness of the peak after acid treatment suggests that the graphitic structure was preserved. The other peaks at 2θ = 43.90°, 53.70° and 78.10° correspond to (100), (004) and (110) reflection planes, respectively. The inter-planar spacing (d) was calculated using Bragg’s law (nλ = 2dsinθ) with the peak at 2θ = 25.70°, and a slight variation was observed between the raw and acid-treated samples. It has been reported that a decrease in the order of crystallinity for CNTs causes the XRD peaks to broaden and shift the (002) reflection plane towards lower angles [31]. Our results are similar to what has been reported previously. In addition, we also observed that functionalising the tubes slightly increased the full width at half maximum (FWHM) from 2.44° with the raw CNTs to 2.47° with the acid-treated CNTs (Table 1). An increase in the FWHM has been reported to be due to long acid treatment times damaging and thus reducing the overall crystallinity of the MWCNTs [31]; however, the slight increase with our results suggests that the treatment protocol removes amorphous carbons and residual catalyst particles without significantly damaging or degrading the overall crystallinity of the MWCNTs.Fig. 1


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

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

a The XRD pattern of raw and acid-treated CNTs. b The wide-angle XRD pattern for SBA-15 samples. c The low-angle XRD pattern for SBA-15. d The wide-angle XRD pattern for various wt% loadings of SBA-15 coated on CNTs
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig1: a The XRD pattern of raw and acid-treated CNTs. b The wide-angle XRD pattern for SBA-15 samples. c The low-angle XRD pattern for SBA-15. d The wide-angle XRD pattern for various wt% loadings of SBA-15 coated on CNTs
Mentions: Figure 1a depicts the XRD patterns of the pristine and acid-treated CNT structures. The characteristic peaks of the CNTs appear at 2θ values of 26.00° and 43.40°. The strong and sharp diffraction peak at 2θ = 25.70 was indexed to the (002) reflection of graphite [30]. The relative sharpness of the peak after acid treatment suggests that the graphitic structure was preserved. The other peaks at 2θ = 43.90°, 53.70° and 78.10° correspond to (100), (004) and (110) reflection planes, respectively. The inter-planar spacing (d) was calculated using Bragg’s law (nλ = 2dsinθ) with the peak at 2θ = 25.70°, and a slight variation was observed between the raw and acid-treated samples. It has been reported that a decrease in the order of crystallinity for CNTs causes the XRD peaks to broaden and shift the (002) reflection plane towards lower angles [31]. Our results are similar to what has been reported previously. In addition, we also observed that functionalising the tubes slightly increased the full width at half maximum (FWHM) from 2.44° with the raw CNTs to 2.47° with the acid-treated CNTs (Table 1). An increase in the FWHM has been reported to be due to long acid treatment times damaging and thus reducing the overall crystallinity of the MWCNTs [31]; however, the slight increase with our results suggests that the treatment protocol removes amorphous carbons and residual catalyst particles without significantly damaging or degrading the overall crystallinity of the MWCNTs.Fig. 1

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