Synthesis and characterization of rare earth metal doped tungsten trioxide photocatalyst for degradation of Rhodamine B dye

Nowadays, it is concern for researchers that due to high recombination rate of photogenerated charge carriers in tungsten trioxide (WO3) nanoparticles, the future applications are limited in the field of photocatalysis. Herein we attempt to synthesize tungsten trioxide nanoparticles with different doping concentrations of lanthanum i.e. 2 wt%, 4 wt%, 6 wt% and 8 wt%. The synthesized samples were characterized by using various characterization techniques: X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), photoluminescence spectra (PL), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) and UV–Vis spectroscopy. WO3 retains its monoclinic structure even after doping which was confirmed by XRD analysis. FTIR helps to descry functional groups present in the samples. The size of nanoparticles was calculated by using TEM. EDX confirms the absence of any impurity in the synthesized samples. Raman spectroscopy confirms the presence of a large number of imperfections induced in the lattice of WO3. The rate of recombination was analyzed by photoluminescence (PL) spectroscopy and is minimum in 4 wt% doping of lanthanum. The optical band-gap was calculated using UV–Vis spectroscopy and becomes narrow along with the doping concentrations. Intriguingly, it is found that doping of La in WO3 has considerably ameliorate the photocatalytic activity by reducing rate of recombination due to the trapping of electrons by defects introduced in the lattice. Photocatalytic decolorization of Rhodamine B (RhB) dye was performed and the values of c/c0 and rate constant (k) confirm that the 4 wt% doping shows maximum degradation efficiency. The kinetic study for photodegradation of Rhodamine B was done by using various kinetic models and results show that the reaction follows first order kinetics very well. Therefore, optimum doping of lanthanum increases the decolorization ability of WO3 towards RhB dye.