Anchoring Perovskite-Like Bi₄Ti₃O₁₂ and Plasmonic Bi on Defect-Rich Yellow TiO_2–<i>x</i> for Enhanced Catalytic Activity toward Degradation of Pollutants upon Visible Light

The efficiency of heterogeneous photocatalytic processes is currently limited due to the fast recombination of photocarriers, poor light absorption, and inefficient surface catalytic characteristics. In this study, defect-rich yellow TiO_2-<i>x</i> nanoparticles (abbreviated as D-TiO₂) with high surface area and significant absorption in the visible range were integrated with perovskite-like Bi₄Ti₃O₁₂ to synthesize binary D-TiO₂/Bi₄Ti₃O₁₂ nanocomposites. To overcome the problem of insufficient activity, we integrated the optimized D-TiO₂/Bi₄Ti₃O₁₂ nanocomposite with plasmonic Bi nanoparticles. Significantly, the optimized D-TiO₂/Bi₄Ti₃O₁₂/Bi-2 nanocomposite efficiently removed tetracycline (TC) in 50 min through production of ^•OH, h⁺, and ^•O₂^- species, whose removal rate promoted 10.6, 3.18, 5.01, and 1.84 compared with the white TiO₂ (abbreviated as W-TiO₂), D-TiO₂, Bi₄Ti₃O₁₂, and D-TiO₂/Bi₄Ti₃O₁₂ (20%) photocatalysts, respectively. The outstanding performance of the D-TiO₂/Bi₄Ti₃O₁₂/Bi photocatalyst was attributed to its quantum dot size, low resistance for charge migration, increased surface area, oxygen vacancies in D-TiO₂, and developed n-n heterojunction among D-TiO₂ and Bi₄Ti₃O₁₂, which accelerated charge transfer and promoted the generation of active species. Furthermore, the stability tests showed that the TC degradation efficiency still reached 96% after four recycles, indicating the remarkable stability of the photocatalyst. Eventually, the biocompatible nature of the treated solution over the optimized photocatalyst was also revealed from an investigation of the growth of lentil seeds.