Hybrid Density Functional Theory Study of Native Defects and Nonmetal (C, N, S, and P) Doping in a Bi₂WO₆Photocatalyst

Abstract

Native defects and nonmetal doping have been shown to be an effective way to optimize the photocatalytic properties of Bi2WO6. However, a detailed understanding of defect physics in Bi2WO6 has been lacking. Here, using the Heyd–Scuseria–Ernzerhof hybrid functional defect calculations, we study the formation energies, electronic structures, and optical properties of native defects and nonmetal element (C, N, S, and P) doping into Bi2WO6. We find that the Bi vacancy (Bivac), O vacancy (Ovac), S doping on the O site (SO), and N doping on the O site (NO) defects in the Bi2WO6 can be stable depending on the Fermi level and chemical potentials. By contrast, the substitution of an O atom by a C or P atom (CO, PO) has high formation energy and is unlikely to form. The calculated electronic structures of the Bivac, Ovac, SO, and NO defects indicate that the band-gap reduction of Ovac 2+, Bivac 3–, and SO defects is mainly due to forming shallow impurity levels within the band gap. The calculated absorption coefficients of Ovac 2+, Bivac 3–, and SO show strong absorption in the visible light region, which is in good agreement with the experimental results. Hence, Ovac 2+, Bivac 3–, and SO defects can improve the adsorption capacity of Bi2WO6, which helps enhance its photocatalytic performance. Our results provide insights into how to enhance the photocatalytic activity of Bi2WO6 for energy and environmental applications through the rational design of defect-controlled synthesis conditions.

Effects of Fluorination and Molybdenum Codoping on Monoclinic BiVO4 Photocatalyst by HSE Calculations

“…The band position and photoelectric thresholds for several compounds have been calculated. 9 , 11 , 51 , 52 …”

The Thermodynamic Stability, Electronic and Photocatalytic Properties of the ZnWO4(100) Surface as Predicted by Screened Hybrid Density Functional Theory

“…The Mulliken electronegativity theory can predict the CB and VB positions of ZnWO 4 , Zn 2 O 4 -Zn 8 W 6 O 28 , and W 2 O 4 -Zn 8 W 10 O 36 terminations: E CB = χ – E c – 0.5 E g (or E VB = χ – E c + 0.5 E g ), where E CB ( E VB ) is the conduction (valence) band position, χ is the absolute electronegativity of bulk ZnWO 4 , Zn 2 O 4 -Zn 8 W 6 O 28 , and W 2 O 4 -Zn 8 W 10 O 36 terminations, E c is the energy of the free electron in the hydrogen scale (approximately 4.5 eV), and E g is the band gap energy of the ZnWO 4 , Zn 2 O 4 -Zn 8 W 6 O 28 , and W 2 O 4 -Zn 8 W 10 O 36 terminations. The band position and photoelectric thresholds for several compounds have been calculated. − …”

The stability and electronic and photocatalytic properties of the ZnWO4 (010) surface determined from first-principles and thermodynamic calculations

“…The band position and photoelectric thresholds for several compounds have been calculated. 55,[67][68][69] As regards the Mulliken electronegativity (c) of compound A a -B b C c , it can be calculated according to the following eqn: 70,71 cðA a B b C c Þ ¼ ðcðAÞ a ðBÞ b ðCÞ c Þ 1 aþbþc , where c(A), c(B), and c(C) are the absolute electronegativity of the A atoms, B atoms, and C atoms, respectively; the a, b, c are the number of A atoms, B atoms, C atoms in an A a B b C c compound. Based on the Mulliken denition, per atom's absolute electronegativity is equal to the arithmetic mean of the atomic electron affinity (A) and the rst ionization energy (I).…”