Enhanced visible light absorption and photocatalytic activity of [KNbO3]1−x[BaNi0.5Nb0.5O3−δ]x synthesized by sol–gel based Pechini method

Abstract

Ba, Ni co-modified KNbO₃ nanocrystals (KBNNO) were synthesized by sol–gel based Pechini method. X-ray diffraction and Raman measurements reveals the phase transformation of KBNNO from orthorhombic to cubic phase with increasing doping ratio x. Particle sizes of KBNNO nanocrystals were measured to range from 50 nm to 200 nm by scanning electron microscopy. X-ray photoelectron spectroscopy and electron dispersive X-ray elemental analysis reveal the elemental composition of KBNNO samples. Ultraviolet-visible-near infrared optical absorption spectra of KBNNO show enhanced visible light absorption compared with pure KNbO₃ synthesized under the same conditions. Photocatalytic activity evaluation displays an enhanced visible light photocatalytic activity of KBNNO in degrading methylene blue in comparison with KNbO₃ and P25 TiO₂. Notably, KBNNO with x = 0.2 displays the greatest photoreactivity compared with KNbO₃ and P25 TiO₂. The mechanism responsible for the enhancement of visible light absorption by Ni²⁺ in KBNNO was discussed, highlighting the crucial role that Ni²⁺ ions have played in the sub-energy levels of KBNNO.