Tailoring TiO2through N doping and incorporation of amorphous carbon nanotubes via a microwave-assisted hydrothermal method

Sithembela A. Zikalala, Rengaraj Selvaraj, Faisal Al Marzouqi, Alex T. Kuvarega, Bhekie B. Mamba, Sabelo D. Mhlanga, Edward N. Nxumalo*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

Abstract

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.

Original languageEnglish
Article number104082
JournalJournal of Environmental Chemical Engineering
Volume8
Issue number5
DOIs
Publication statusPublished - Oct 1 2020

Keywords

  • amorphous carbon nanotubes
  • amorphous nitrogen-doped carbon nanotubes
  • Congo Red dye
  • microwaves
  • photocatalysis

ASJC Scopus subject areas

  • Chemical Engineering (miscellaneous)
  • Waste Management and Disposal
  • Pollution
  • Process Chemistry and Technology

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