DFT Investigation on the Electronic and Water Adsorption Properties of Pristine and N-Doped TiO2 Nanotubes for Photocatalytic Water Splitting Applications

• Published in: Journal of electronic materials 2017-06, Vol.46 (6), p.3592-3602
• Main Authors: Enriquez, John Isaac G., Moreno, Joaquin Lorenzo V., David, Melanie Y., Arboleda, Nelson B., Lin, Ong Hui, Villagracia, Al Rey C.
• Format: Article
• Language: English
• Subjects: Adsorbed water; Adsorption; Anatase; Characterization and Evaluation of Materials; Chemistry and Materials Science; Density functional theory; Doping; Electronic properties; Electronics and Microelectronics; Energy levels; Energy of dissociation; Hydrogen production; Hydroxyl radicals; Instrumentation; Materials Science; Nanotubes; Nitrogen; Optical and Electronic Materials; Photocatalysis; Solid State Physics; Titanium dioxide; Valence band; Water splitting
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-017-5342-y

Experimental studies have shown the production of hydrogen through a photocatalytic water splitting process using a titanium dioxide nanotube (TiO 2 NT) as a photoelectrode. In this study, a theoretical model of pristine and nitrogen-doped TiO 2 NT based on a TiO 2 anatase (101) surface is presented. Spin unrestricted density functional theory calculations were performed to provide a detailed description of the geometries, electronic properties, and adsorption of water (H 2 O) on pristine and N-doped TiO 2 NT. The calculations show that doping with N will improve the photocatalytic properties of TiO 2 NT in two ways: First, the energy barrier of the dissociation reaction of water into hydroxyl radical and hydrogen atom is reduced; and second, the defect-induced states above the valence band lowers the band gap which will result in enhanced visible-light-driven photoactivity. Based on the position of the Fermi level relative to the defect induced energy levels, an optimal doping concentration of around 1.4% is proposed, which is in good agreement with experimental results. This study provides an atomic/molecular level understanding of the photocatalytic water splitting process and may serve as a groundwork for the rational design of more efficient photocatalysts.