Programme

P.57 -- Posters, VCTP-50

Date: Thursday, 7 August 2025

Time: 08:30 - 10:00

The effect of oxygen vacancy concentration on structural, electronic and optical properties of Bi2WO6 photocatalyst: DFT study

Doan Thi Hiena, Tran Phan Thuy Linha, Luc Huy Hoanga,b and Pham Van Haia,b,*

aFaculty of Physics, Hanoi National University of Education, Hanoi, Vietnam bInstitute of Natural Sciences, Hanoi National University of Education, Hanoi, Vietnam 136 Xuanthuy St, Caugiay district, Hanoi, Vietnam

In this study, the effects of oxygen vacancy (OV) concentration on the structural, electronic, and optical properties of Bi₂WO₆ photocatalyst were systematically investigated using density functional theory (DFT). Six different oxygen-deficient models were constructed with vacancy concentrations ranging from 0 to 25%, corresponding to 1–6 missing oxygen atoms in the Bi₂WO₆ lattice. Structural analysis revealed that increasing OV concentration induces significant lattice distortion, modifies Bi–O coordination environments, and affects unit cell parameters, especially causing abrupt expansion along the b-axis and unit cell volume at higher defect densities. Electronic structure calculations show that the introduction of OVs creates impurity states near the conduction band, resulting in reduced band gap energy from 2.326 eV to below 0.5 eV. Electron density difference (EDD) maps and Bader charge analysis indicate progressive electron accumulation near vacancy sites, suggesting the formation of F-centers and partial reduction of Bi³⁺ to Bi²⁺. These electronic modifications enhance the n-type conductivity of Bi₂WO₆. Optical property analysis demonstrates a visible-light red-shift in absorption edges and the emergence of new low-energy peaks in both absorption and dielectric function spectra, attributed to OV-induced defect states. The results suggest that moderate oxygen vacancy concentrations can effectively tune the electronic structure and optical response of Bi₂WO₆, offering a promising strategy to enhance its photocatalytic performance.

Presenter: Doan Thi Hien