Abstract
On the basis of time-dependent density functional theory (TD-DFT) we performed first-principle calculations to predict optical properties and transition states of pristine, N- and S-doped, and N+S-codoped anatase TiO nanotubes of 1 nm-diameter. The host O atoms of the pristine TiO nanotube were substituted by N and S atoms to evaluate the influence of dopants on the photocatalytic properties of hollow titania nanostructures. The charge transition mechanism promoted by dopants positioned in the nanotube wall clearly demonstrates the constructive and destructive contributions to photoabsorption by means of calculated transition contribution maps. Based on the results of our calculations, we predict an increased visible-light-driven photoresponse in N- and S-doped and the N+S-codoped TiO nanotubes, enhancing the efficiency of hydrogen production in water-splitting applications.
Highlights
Use of photodriven semiconductor-based catalyst is a promising route for energy production from sunlight
The band gap width of TiO2 allows efficient water-splitting under UV irradiation due to the positions of band edges—valence band maximum (VBM) of TiO2 is located below the oxidation potential of water, while its conduction band minimum (CBM) is located above the proton reduction potential in many synthesized TiO2 -based compounds [2,3,4,5,6,7,8,9,10,11,12]
We demonstrated that the combination of N and S dopants replacing the host oxygen atoms in TiO2 NT can enhance the visible-light-driven photoresponse and cause redshift of TiO2 NT absorption spectra under the conditions necessary for water splitting
Summary
Use of photodriven semiconductor-based catalyst is a promising route for energy production from sunlight. The relatively wide band gap of undoped TiO2 leads to relatively poor efficiency of light absorption in the visible range of solar spectrum. The total efficiency of the photocatalytic process strongly depends on charge transport and charge separation processes taking place in photocatalytic materials. In this respect, one-dimensional hollow nanostructures exhibit unique and advantageous features in comparison with three-dimensional and two-dimensional phases of photocatalytic materials [13]. The quantum confinement effect leads to a slightly increased band gap of nanotubes (NTs).
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