Manganese and Nitrogen co-doped TiO 2 for the photocatalytic degradation of anionic dyes and phenol under sunlight

Different compositions of manganese (x = 1 & 3 wt. %) and nitrogen (y = 1 wt. %) co-doped TiO2 (MnxNyT) photocatalysts are prepared by the conventional sol-gel method. The crystallinity, optical properties, phase purity and surface morphology of prepared nano-photocatalysts were characterised in detail. The structural analyses show that the simultaneous doping with manganese and nitrogen controls the growth of TiO2 crystal structure having an average crystallite size in the range of 14.6 to 24.5 nm. The optical analysis also demonstrated that due to the synergistic effect of Mn and N, co-doped TiO2 represents the red-shift in the absorption band edge from 3.33 eV to 2.39 eV, which improved the response of TiO2 structure towards the visible region and enhanced electron-hole separation. Among all, Mn3N1T represented the better photocatalytic efficiency against anionic dyes (Blue KBR and Red GD) and phenol under optimised conditions (such as initial substrate's concentration = 20 ppm, photocatalyst dose = 0.5 g and solution pH of 3 and 7, respectively) due to its low bandgap, low crystallite size and high absorptivity towards the visible region. The kinetics study also showed that the degradation of dyes and phenol over Mn3N1T followed pseudo-first-order kinetics.