TiO₂/Bi₂O₃/PANI nanocomposite materials for enhanced photocatalytic decontamination of organic pollutants

In this present work, TiO₂/Bi₂O₃/PANI nanocomposites were synthesized and employed as photocatalyst for the degradation of organic pollutants i.e. Rhodamine B dye and Triclopyr pesticides. TiO₂/Bi₂O₃/PANI nanocomposites were characterized with the help of various advanced instrumentation techniques including X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (UV–vis DRS), photoluminescence (PL), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) analysis. The absorption in the visible wavelength region (λ > 400 nm) increased with increasing PANI amount accompanied by π →π^∗ transition. The close contact between TiO₂, Bi₂O₃ and PANI promotes the interfacial charge transfer and significantly improved photocatalytic performance under the irradiation of visible LEDs. Among the prepared nanocomposites, the sample containing 5 wt% PANI of TiO₂/Bi₂O₃(TB(15)) was found to be most efficient photocatalyst and stable even after four cyclic runs for the degradation of organic pollutants. TB(15)/PANI(5) exhibited the lowest PL intensity, indicating the minimum reunion in the photoproduced electron-hole pairs, which was favorable to improve the efficiency of the photocatalyst for the removal of organic pollutants. The photodegradation rate of RhB and TC using TB(15)/PANI(5) photocatalyst reached to 99.6% in 50 min and 76.1% in 120 min under the visible LEDs irradiation respectively. Kinetics analysis of photocatalytic reaction obeys the pseudo first-order kinetic model with respect to concentration of organic pollutants with a regression coefficient value in the range of 0.941–0.999. The trapping experiments confirmed that holes are prominent species for the degradation of RhB, and holes and superoxide anion radical for photocatalytic degradation of TC. Finally, the mechanism of photocatalytic degradation using TiO₂/Bi₂O₃/PANI nanocomposite was also proposed.