Synthesis and characterization of visible light absorbing nanosized (1-x)KNbO_3-x(BaNi_1/2Nb_1/2O_3-𝛿) (x = 0, 0.05, 0.1, 0.15 and 0.2) by solution combustion method and its enhanced photocatalytic activity

Nanosized (1-x)KNbO_3-x(BaNi_1/2Nb_1/2O_3-𝛿) (KBNNO) (x = 0-0.2) powders with an interval of 0.05 were prepared by solution combustion method using citric acid as the fuel. The effect of fuel to oxidizer (F/O) ratio on phase evolution and combustion process was studied and we observed that complete phase formation occurs at 600°C for 𝜑_e = 0.55. XRD and Raman analysis confirm that with increase in dopant content, gradual changes occur in phase transition from orthorhombic to cubic. Ba, Ni co-doping made KNbO3_, visible light active, which was confirmed by UV–Vis absorption spectra. Photocatalytic experiments show that KBNNO 0.1 exhibited better photocatalytic activity in degrading RhB under visible light irradiation compared to KNbO₃ and P25 (commercial TiO₂-based photocatalyst). The rate constant of KBNNO 0.1 for RhB degradation is 3.17 and 1.4 times higher than KNbO₃ and P25, respectively, under similar visible light illumination. The mechanisms behind photocatalytic activity and photo stability have also been studied for the best composition. (author)