TY - JOUR
T1 - Tailoring TiO2through N doping and incorporation of amorphous carbon nanotubes via a microwave-assisted hydrothermal method
AU - Zikalala, Sithembela A.
AU - Selvaraj, Rengaraj
AU - Al Marzouqi, Faisal
AU - Kuvarega, Alex T.
AU - Mamba, Bhekie B.
AU - Mhlanga, Sabelo D.
AU - Nxumalo, Edward N.
N1 - Funding Information:
The authors would like to acknowledge the assistance of Dr. Bridget Mutuma of the Department of Applied Materials, University of Pretoria , Prof. Neil Coville, Alice Magubane and Victor Mashindi of the DST-NRF Centre of Excellence in Strong Materials and the Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand for granting permission and due diligence in assisting with the synthesis of the carbonaceous materials. We would also like to acknowledge Dr. Sefako Mofokeng and Dr. Fokotsa Molefe of the department of Physics for assistance with Photoluminescence spectroscopic analysis.The authors would like to thank the University of South Africa, Nanotechnology and Water Sustainability Research Unit and the National Research Foundation for funding the research .
PY - 2020/10
Y1 - 2020/10
N2 - Nanohybrids consisting of titanium dioxide (TiO2) and amorphous carbon nanotubes (aCNTs) or amorphous nitrogen-doped carbon nanotubes (aNCNTs) were synthesized using the microwave radiation-assisted hydrothermal method in order to investigate the effect of CNTs on the physicochemical, optical and photocatalytic properties of doped and undoped TiO2. The synthesized nanohybrids consisted of titania-aCNT (TiO2-aCNT), titania-aNCNT (TiO2-aNCNT), and nitrogen doped titania-aNCNT (NTiO2-aNCNT). Pristine NTiO2was also synthesized as a control. It was observed that a small amount of aCNTs and aNCNTs (3wt.%) causes a significant difference in the physicochemical properties of the TiO2nanohybrids such as particle size, particle size distribution, aggregation and optical properties. The presence of aNCNTs and aCNTs improves particle dispersion, reduces particle size and the size distribution for both TiO2and NTiO2. In addition, aCNTs or aNCNTs promote the formation of spherical TiO2and cuboidal NTiO2nanoparticles as opposed to the nanosheets in NTiO2. Both carbonaceous materials also suppress electron-hole recombination, thus enhancing the photocatalytic activity of the nanohybrids. A strong correlation between the CNT loading and the physicochemical, optical properties and photodegradation of Congo Red dye of the nanohybrids was observed. For example, the nanohybrid TiO2-aNCNT exhibited the smallest particle size and size distribution (6.18±1.25nm), the lowest energy band gap (3.02eV) the lowest PL intensity and thus the highest photocatalytic efficiency (99.2 % in 30min with k1 app=41.2×10-3min-1) with TiO2-aCNT being the second best in terms of particle size (7.06±1.48nm), energy band gap (3.04eV) and hence the CR removal rate at 30min (99.8 %). Furthermore, a comparison of the least performing photocatalyst NTiO2and NTiO2-aNCNT shows that while the incorporation of aNCNT into NTiO2increases the energy band gap from (3.15-3.19)eV, it still enhances the NTiO2particle dispersion and reduce the PL intensity. As a result, NTiO2has less overall removal of CR 63.3 % than NTiO2-aNCNT (82.6 %). Lastly, the incorporation of the carbonaceous materials promotes the second order adsorption kinetics and improves the photocatalytic performance of the nanohybrids.
AB - Nanohybrids consisting of titanium dioxide (TiO2) and amorphous carbon nanotubes (aCNTs) or amorphous nitrogen-doped carbon nanotubes (aNCNTs) were synthesized using the microwave radiation-assisted hydrothermal method in order to investigate the effect of CNTs on the physicochemical, optical and photocatalytic properties of doped and undoped TiO2. The synthesized nanohybrids consisted of titania-aCNT (TiO2-aCNT), titania-aNCNT (TiO2-aNCNT), and nitrogen doped titania-aNCNT (NTiO2-aNCNT). Pristine NTiO2was also synthesized as a control. It was observed that a small amount of aCNTs and aNCNTs (3wt.%) causes a significant difference in the physicochemical properties of the TiO2nanohybrids such as particle size, particle size distribution, aggregation and optical properties. The presence of aNCNTs and aCNTs improves particle dispersion, reduces particle size and the size distribution for both TiO2and NTiO2. In addition, aCNTs or aNCNTs promote the formation of spherical TiO2and cuboidal NTiO2nanoparticles as opposed to the nanosheets in NTiO2. Both carbonaceous materials also suppress electron-hole recombination, thus enhancing the photocatalytic activity of the nanohybrids. A strong correlation between the CNT loading and the physicochemical, optical properties and photodegradation of Congo Red dye of the nanohybrids was observed. For example, the nanohybrid TiO2-aNCNT exhibited the smallest particle size and size distribution (6.18±1.25nm), the lowest energy band gap (3.02eV) the lowest PL intensity and thus the highest photocatalytic efficiency (99.2 % in 30min with k1 app=41.2×10-3min-1) with TiO2-aCNT being the second best in terms of particle size (7.06±1.48nm), energy band gap (3.04eV) and hence the CR removal rate at 30min (99.8 %). Furthermore, a comparison of the least performing photocatalyst NTiO2and NTiO2-aNCNT shows that while the incorporation of aNCNT into NTiO2increases the energy band gap from (3.15-3.19)eV, it still enhances the NTiO2particle dispersion and reduce the PL intensity. As a result, NTiO2has less overall removal of CR 63.3 % than NTiO2-aNCNT (82.6 %). Lastly, the incorporation of the carbonaceous materials promotes the second order adsorption kinetics and improves the photocatalytic performance of the nanohybrids.
KW - amorphous carbon nanotubes
KW - amorphous nitrogen-doped carbon nanotubes
KW - Congo Red dye
KW - microwaves
KW - photocatalysis
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U2 - 10.1016/j.jece.2020.104082
DO - 10.1016/j.jece.2020.104082
M3 - Article
AN - SCOPUS:85087887508
SN - 2213-3437
VL - 8
JO - Journal of Environmental Chemical Engineering
JF - Journal of Environmental Chemical Engineering
IS - 5
M1 - 104082
ER -