  The band gap of SrTiO$_{3}$ retards its photocatalytic application.
Regardless narrowing the band gap of the anion doped SrTiO$_{3}$, the anion
doping structures have low photoconversion efficiency. The co-cation dopings
are used to modify the band gap and band edges positions of SrTiO$_{3}$ to
enhance the photocatalyitic properties by extending the absorption to longer
visible-light. Using density functional calculations with the
Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional for exchange-correlation, the
crystal and electronic structures as well as the optical properties of the mono
and codped SrTiO$_{3}$ are investigated. The (Mo, Zn/Cd) and (Ta, Ga/In)
codoped SrTiO$_{3}$ are explored in the way to retain the semiconductor
characteristics of the latter. It is found that (Ta, Ga/In) codoping does not
enhance the photocatalytic activity of SrTiO$_3$ due to its large band gap.
Moreover, the position of the conduction band edge of the (Mo, Cd) monodoping
impedes the photocatalytic efficiency. The obtained results indicate that (Mo,
Zn) codoped SrTiO$_3$ can potentially improve the photocatalyitic activity.
