Role of F in Improving the Photocatalytic Activity of Rh-Doped SrTiO3 (original) (raw)

The Journal of Physical Chemistry C

Abstract

ABSTRACT In this study, the effect of F doping on the electronic structure and photocatalytic activity of Rh-doped SrTiO3 has been investigated using hybrid density functional theory as a tool. Although doping with only Rh significantly enhances the visible light activity, the photo-conversion efficiency has been found to be poor. This is due to Rh+4 state, which introduces localized unoccupied states above the valence band and promotes the electron-hole recombination process. Upon codoping with F, the localized states are found to be completely passivated. Analysis of Bader charge indicates the existence of lower oxidation state of Rh in the (Rh, F)-codoped SrTiO3. The valence band maxima is elevated significantly due to strong hybridization of O 2p orbital and Rh 4d orbital, resulting in band gap narrowing to 2.50 eV. The nature of band structure of (Rh, F)-codoped SrTiO3 is found to be strongly dependent on the relative proportion of the dopant elements. 1:2 (Rh, F) codoping not only results into a clean band structure but also reduces the band gap by a larger extent (0.88 eV). In the case of 2:1 (Rh, F)-codoping, localized unoccupied states in the forbidden region are still present. Calculation of the defect formation energy indicates that the doping of Rh becomes more feasible in presence of F. The relative locations of the band edge for both 1:1 and 1:2 (Rh, F)-codoped SrTiO3 are found to be suitable for the overall water splitting process. Hence, introduction of F is expected to enhance the photocatalytic activity of Rh-doped SrTiO3 under visible light due to narrowing of the band gap as well as lowering of electron-hole recombination rate.

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