Effective catalytic performance of manganese and phosphorus co-doped titania nanocatalyst for Orange-II dye degradation under visible light irradiation

• The nano catalysts were synthesized by cost effective simple sol–gel method.
• Due to phosphorous doping band gap of TiO2 is decreased and with manganese doping electron hole recombination is prevented.
• All the catalysts were in anatase phase which is most suitable for photocatalytic degradations.
• The co-doped photocatalysts have band gap ranging from 2.77 to 2.95 eV making them active in visible region.
• The particle size was found to be 7 nm favouring the photocatalytic degradation due to more surface area.
• The kinetics of degradation of an azo dye by photocatalysts was studied under different conditions like pH, catalyst dosage; dopant concentration, initial dye concentrations and finally optimum conditions were established.

Co-doped nano titania was prepared by doping with varying weight percentages of phosphorus (P) and manganese (Mn) by sol–gel method for eventual application in degradation of dyes. Co-doping reduces the band gap of TiO2 and shows an effective degradation of dye in visible light. The as prepared catalysts were characterized by X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (UV–DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and fourier transform infra red spectroscopy (FT-IR). The XRD data of the catalysts revealed that the synthesized samples were in anatase phase with 2θ at 25.3°. The XPS results indicated that the P and Mn were present in TiO2 as P5+ and Mn4+/Mn3+. UV–DRS spectra showed a significant absorption shift from ultraviolet to visible region. The doping pattern of P and Mn in TiO2 were determined by FT-IR, the stretching frequencies attributed that they have substituted Ti in TiO2 lattice. Based on TEM results the particle sizes were found to be ranging from 6.8 to 9.6 nm. Photocatalytic efficiency of synthesized nano materials was tested with non-biodegradable Orange-II, an azodye pollutant under visible light. The kinetics of degradation of the dye was studied under different conditions such as pH, catalyst dosage, dopant concentration, initial dye concentrations and finally optimum conditions were established. The P/Mn co-doped TiO2 showed better (11 fold) photocatalytic performances than undoped TiO2. The reactive species such as OH radicals which are formed in the reaction were tested by photoluminescent spectroscopy (PL).