Low temperature RF plasma nitriding of self-organized TiO2 nanotubes for effective bandgap reduction

• Published in: Applied surface science Vol. 442; pp. 239 - 244
• Main Authors: Bonelli, Thiago Scremin, Pereyra, Inés
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-06-2018
• Subjects: Bandgap reduction; Nanotubes; Nitriding; Photocatalysis; TiO2; Nitriding; Bandgap reduction; Photocatalysis; Nanotubes; TiO2
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2018.02.153

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•Nitriding of self-organized TiO2 nanotubes in PECVD reactor is proposed.•Bandgap reduction of self-organized TiO2 nanotubes.•Increase in photocatalytic activity of self-organized TiO2 nanotubes.
Titanium dioxide is a widely studied semiconductor material found in many nanostructured forms, presenting very interesting properties for several applications, particularly photocatalysis. TiO2 nanotubes have a high surface-to-volume ratio and functional electronic properties for light harvesting. Despite these manifold advantages, TiO2 photocatalytic activity is limited to UV radiation due to its large band gap. In this work, TiO2 nanotubes produced by electrochemical anodization were submitted to plasma nitriding processes in a PECVD reactor. The plasma parameters were evaluated to find the best conditions for gap reduction, in order to increase their photocatalytic activity. The pressure and RF power density were varied from 0.66 to 2.66 mbar and 0.22 to 3.51 W/cm2 respectively. The best gap reduction, to 2.80 eV, was achieved using a pressure of 1.33 mbar and 1.75 W/cm2 RF power at 320 °C, during a 2-h process. This leads to a 14% reduction in the band gap value and an increase of 25.3% in methylene blue reduction, doubling the range of solar photons absorption from 5 to 10% of the solar spectrum.