Enhanced photocatalytic performance of spherical BiOI/MnO₂ composite and mechanism investigation

In this paper, a novel flower-like BiOI/MnO₂ composite was synthesized by two simple steps. The crystal structure, morphology, surface element analysis, and optical properties of as-prepared samples were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV-Vis diffuse reflectance spectrometry (DRS). Photocatalytic activities of the prepared photocatalysts were evaluated by photocatalytic degradation of RhB under simulated light irradiation. When 50 mg of a BiOI/MnO₂ composite with a mass ratio of 5/1 was used to degrade RhB aqueous solution (100 mL, 20 mg L^-1), the degradation efficiency could reach 99.18% within 60 min under simulated solar light irradiation. In addition, the photocatalyst exhibited good stability. After four cycles, the degradation efficiency of the BiOI/MnO₂ (5/1) composite could reach 92.8% within 80 min. The probable photocatalytic mechanism of photocatalysts was investigated by active species trapping experiments and photoluminescence (PL) measurements. The results showed that the superior photocatalytic activity of the BiOI/MnO₂ composite is derived from the generation and transfer of photogenerated carriers between MnO₂ and BiOI.