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

Highlights: • The water splitting photocatalytic properties of (1 1 1) TaON nanosheet. • Effect of Nb and V doping, and Nb-V co-doping on the photocatalytic properties. • (1 1 1) Nb_0.25Ta_0.75ON nanosheet was the best water splitting photocatalyst. • V doped and Nb-V co-doped (1 1 1) TaON nanosheets were suitable n-type photocatalysts. The water splitting photocatalytic properties of the pristine, Nb/V doped, and Nb-V co-doped (1 1 1) 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 (1 1 1) 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 (1 1 1) 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 (1 1 1) 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 (1 1 1) TaON nanosheets, the (1 1 1) Nb_0.25Ta_0.75ON and Nb_0.125Ta_0.875ON nanosheets with CB edge energy of −4.37 and −4.30 eV were more suitable for water splitting photocatalyst than pristine (1 1 1) TaON nanosheet. The calculations on the Nb-V co-doped (1 1 1) TaON nanosheets showed them as appropriate n-type water splitting photocatalysts.