Role of F in Improving the Photocatalytic Activity of Rh-Doped SrTiO₃

Abstract

In this study, the effect of F doping on the electronic structure and photocatalytic activity of Rh-doped SrTiO 3 has been investigated using hybrid density functional theory as a tool. Although doping with only Rh significantly enhances the visible light activity, the photoconversion efficiency has been found to be poor. This is due to the 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 the lower oxidation state of Rh in the (Rh, F)codoped SrTiO 3 . The valence band maxima are elevated significantly due to strong hybridization of the O 2p orbital and Rh 4d orbital, resulting in band gap narrowing to 2.50 eV. The nature of the band structure of (Rh, F)codoped SrTiO 3 is found to be strongly dependent on the relative proportion of the dopant elements. 1:2 (Rh, F) codoping not only results in 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 the presence of F. The relative locations of the band edge for both 1:1 and 1:2 (Rh, F)-codoped SrTiO 3 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 SrTiO 3 under visible light due to narrowing of the band gap as well as lowering of the electron−hole recombination rate.

Improvement of BiVO4 Photoanode Performance During Water Photo‐Oxidation Using Rh‐Doped SrTiO3 Perovskite as a Co‐Catalyst

“…SrTiO 3 is a highly stable perovskite semiconductor, in which the trace noble metal Rh can exist stably in the crystal structure as a dopant. In recent years, the research on Rh‐SrTiO 3 has mainly focused on photocatalytic hydrogen evolution and construction of the Z‐scheme with BiVO 4 due to its negative conduction band . It is well known that the Z‐scheme used for overall water splitting generally consists of three sections: hydrogen evolution photocatalysts, oxygen evolution photocatalysts, and electron mediators .…”

Theoretical study on cation codoped SrTiO3 photocatalysts for water splitting

“…Theoretically, (V/Nb/Ta, N) [36], (Sb, N) [37], (Mo/W, 2N) [38], (La/Ce/Pr/Nd, N) [39], and (Rh, 2F) [40] codoping has been studied, the latter turning out to be appropriate for water splitting. Cation-cation codoping has been addressed experimentally for (Ag, Nb) [41] and (La, Cr) [42], showing that visible light absorption is not possible, and theoretically for (Na/K/V/Nb/Ta, Rh) [36] and (La, Rh) [43], finding that (Rh, V) codoping is advantageous for water splitting.…”

Enhanced photoelectrochemical performance of anatase TiO2 for water splitting via surface codoping

“…Note that to reach a stable oxidation state (Rh 3+ ), the Rh dopant needs to transfer an electron from a neighboring O atom to itself (Rh 4+ ). 45 Moreover, the unoccupied impurity states located at 1.73 eV above the VBM can act as deep acceptor energy levels. Additionally, these acceptor states are rather localized, thus would have an adverse inuence on the photocatalytic performance since the carrier mobility drastically reduces and the photogenerated carrier recombination increases.…”