Theoretical investigation of the water splitting photocatalytic properties of pristine, Nb and V doped, and Nb-V co-doped (111) TaON nanosheets

[Display omitted] •The water splitting photocatalytic properties of (111) TaON nanosheet.•Effect of Nb and V doping, and Nb-V co-doping on the photocatalytic properties.•(111) Nb0.25Ta0.75ON nanosheet was the best water splitting photocatalyst.•V doped and Nb-V co-doped (111) TaON nanosheets were suitable n-type photocatalysts. The water splitting photocatalytic properties of the pristine, Nb/V doped, and Nb-V co-doped (111) nanosheets of β-TaON have been studied using the density functional theory (DFT) employing the PBE-U method. The calculated valance (VB) and conduction band (CB) energy edges of (111) TaON nanosheet were −6.67 and −4.17 eV, respectively with the bandgap of 2.49 eV. Doping Nb and V ions in the nanosheet structure mainly affected the CB and decreased the energy bandgap. Also, by increasing dopant concentration, the CB edge and bandgap energy of Nb/V doped (111) TaON nanosheets decreased. Doping V ions decreased the CB edge of nanosheet more than doping Nb ions so that the CB edge of V doped (111) TaON nanosheets were located at lower energy levels compared to the H+/H2 reduction potential, thus, the V doped nanosheets can only be used as n-type water splitting nanosheets. Among considered Nb doped (111) TaON nanosheets, the (111) Nb0.25Ta0.75ON and Nb0.125Ta0.875ON nanosheets with CB edge energy of −4.37 and −4.30 eV were more suitable for water splitting photocatalyst than pristine (111) TaON nanosheet. The calculations on the Nb-V co-doped (111) TaON nanosheets showed them as appropriate n-type water splitting photocatalysts.