Enhanced photocatalytic activity in RhB dye degradation by Mn and B co-doped mixed phase TiO2 photocatalyst under visible light irradiation

Abstract

Here, we report synthesis of undoped, manganese (Mn) doped, boron (B) doped and Mn-B co-doped TiO2 nanoparticles (NPs) by a cost-effective sol-gel method. The structural properties, phase, micro-morphology and particle size of the synthesized nanoparticles have been characterized by X-ray diffraction, Raman spectroscopy, Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS) techniques. These studies revealed that undoped and mono (Mn/B) doped TiO2 NPs exhibit only anatase phase, whereas (Mn and B) co-doped TiO2 NPs exhibit anatase and rutile mixed phase structure. Furthermore, co-doping reduces the particle size, agglomeration in aqueous medium and the sample possesses crystal defects. UV–Visible diffusive reflectance spectroscopy (DRS) revealed that the co-doped sample demonstrates extended optical response in the visible wavelength range of the solar spectrum and is red shifted when compared to undoped and mono doped TiO2 NPs. The obtained optical band gap (2.11 eV) and the Urbach energy (1.12 eV) for the Mn and B co-doped TiO2 NPs suggest the formation of mid-gap energy states, which might make this NPs a suitable candidate for photocatalysis in the visible light spectrum. We investigated the photocatalytic degradation of rhodamine B (RhB) dye by the synthesized NPs under visible light irradiation. Our studies revealed that co-doped TiO2 photocatalyst can degrade 99% of RhB dye within 90 min of visible light irradiation and can retain 95% degradation efficiency up to the third consecutive cycles. Finally, we provide a plausible explanation for such enhanced visible light assisted photocatalytic performance.