Facile integration of brown TiO_2−x with Bi₄V₂O₁₁ and BiVO₄: Double S-scheme mechanism for exceptional visible-light photocatalytic performance in degradation of pollutants

Heterogeneous photocatalysis has been denoted as a promising approach to dealing with environmental and energy crises. Herein, quantum dots (QDs) of TiO_2−x/Bi₄V₂O₁₁/BiVO₄ (T_OVBBV) heterojunction photocatalysts were successfully synthesized through a facile one-pot hydrothermal process with varying amounts of integrated Bi₄V₂O₁₁ and BiVO₄ semiconductors. The resultant photocatalysts were characterized by XPS, FT-IR, EDX, XRD, PL, EIS, SEM, TEM, HRTEM, BET, and UV–vis DRS techniques, and their photocatalytic efficiencies were examined via removing tetracycline (TC), azithromycin (AZi), and rhodamine B (RhB) under visible-light illumination. The results showed exceptionally promoted photocatalytic degradation efficiencies of the studied pollutants using the ternary T_OVBBV-2 nanocomposite. The T_OVBBV-2 nanocomposite was 45.4, 11.6, and 19.8-times more effective than TiO₂, 7.24, 5.85 and 2.34-folds better than TiO_2−x, and 9.81, 9.23, and 1.61-times more effective than Bi₄V₂O₁₁/BiVO₄ for photooxidation of TC, AZi, and RhB, respectively. The significant enhancement in the photocatalytic efficacy of the T_OVBBV-2 nanocomposite originated from the defective oxygen sites in the titanium dioxide structure, which subsequently facilitated the transfer of photo-induced charge carriers through the formed tandem n-n heterojunctions amongst TiO_2−x, Bi₄V₂O₁₁, and BiVO₄ components. In addition to high photocatalytic activities, the T_OVBBV-2 photocatalyst demonstrated good photostability and durability after concurrent applications. This work recommends the T_OVBBV photocatalyst for facile photocatalytic treatment of pollutants owing to its simple preparation route, high degradation outcomes, and robust structure for practical applications.