Investigations on the Phase Transformation, Optical Characteristics, and Photocatalytic Activity of Synthesized Heterostructured Nanoporous Bi 2 O 3 –TiO 2

Fine‐powdered, heterostructured, nanoporous Bi 2 O 3 –TiO 2 ( BTO ) was synthesized by a green approach using ultrasonication, with the mole ratio Bi/Ti of 1:1 and calcined at different temperatures. The physical and optical properties of the mixed oxides were investigated. The phase structure, as identified by X‐ray diffraction ( XRD ), showed the appearance of new phases as a function of the calcination temperature. Morphological examinations indicated the formation of a nanoporous structure with a drastic change in morphology at the calcination temperature of 850°C from a globule to a rod‐shaped structure, which further got transformed to a rocky appearance at 1200°C. Doping with Bi 2 O 3 led to the lowering of the bandgap of TiO 2 from 3.25 to 2.5 eV . A BTO nanocatalyst calcined at 450°C exhibited promising photocatalytic activity for the degradation of quinalphos ( QP ) (92%) after a time interval of 100 min under visible light and at the optimum pH 8. The kinetics of degradation of QP showed that it follows a pseudo‐first‐order path with a rate constant 0.01267 min −1 . The synthesized BTO mixed oxide showed profound improvement in photocatalytic activity in the visible region as compared to TiO 2 .