Improved photocatalytic degradation of Rhodamine B dye using Bi0.5Na0.5TiO3 ferroelectric nanoparticles: Optimization of pH and poling

We report the optimization of the photocatalytic parameters (pH and corona-poling) for Rhodamine B (RhB) dye degradation over Bi_0.5Na_0.5TiO₃ (BNT) nanoparticles under UV–vis light. The BNT nanoparticles were synthesized by the sol-gel method and the XRD analysis confirmed the monoclinic phase structure with Cc space group. No structural distortions were induced by corona-poling, which was confirmed by Raman Spectroscopy. The average size of the nanoparticles was 152 ​nm with irregular morphology as observed by SEM. The optical bandgap of the sample was 3.23 ​eV, as derived from the absorbance spectra of the sample. The optimized conditions achieved for photocatalytic degradation were at a catalyst dosage of 50 ​mg BNT/50 ​mL of 10 ​ppm RhB dye solution and pH value 2. The degradation efficiency of the poled BNT sample for RhB dye at pH value 2 was found to be 96.19 % in just 60 ​min. Complete decolorization was attained after 90 ​min of irradiation. In this process, degradation followed the pseudo-first order kinetics, with a kinetic rate constant of approximately 0.08804 min⁻¹, which is around 27 times higher than the rate constant of BNT nanoparticles with dye. A detailed mechanism for the degradation of dye molecules based on pH and poling effect has also been proposed. Based on these results, BNT photocatalyst can be a promising candidate for the treatment of organic dyes.