Construction of La-doped TiO2@La-doped ZnO–B-doped reduced graphene oxide ternary nanocomposites for improved visible light photocatalytic activity

Abstract

In this study, I demonstrated that the doping of TiO₂, TiO₂@ZnO and reduced graphene oxide (RGO) by rare earth lanthanum ion (La³⁺) and boron (B) is an effective way to enhance photocatalytic visible light activity. The 0.02 mol% La/TiO₂@0.02 mol% La/ZnO, B–RGO–TiO₂, B–RGO-0.08% La/TiO₂, RGO-0.08% La/TiO₂@0.08% La/ZnO, and x mol% La/TiO₂@x mol% La/ZnO-15 wt% B–RGO (x = 0.04, 0.06, 0.08) ternary nanocomposites (TNCs) were prepared via a facile sol–gel technique. The resulting binary and ternary nanohybrid photocatalysts were used for degradation of methylene blue (MB) aqueous solution under visible light illumination as a new probe pollutant. The structure, surface morphology and area, band gap, and chemical composition of the composites were studied using scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, UV-visible diffuse reflectance spectroscopy (DRS) and N₂ adsorption–desorption isotherm (BET) measurements. XRD results showed that 0.02 mol% La/TiO₂@0.02 mol% La/ZnO and x mol% La/TiO₂@x mol% La/ZnO-15 wt% B–RGO TNCs have anatase and wurtzite crystallites phases. The DRS analysis indicated that the absorption of the 0.08 mol% La/TiO₂@0.08 mol% La/ZnO-15 wt% B–RGO TNC shifted to longer wavelength regions (red shift) as well as narrower band gap. The 0.08 mol% La/TiO₂@0.08 mol% La/ZnO-15 wt% B–RGO TNC showed high photocatalytic decomposition of MB under visible light irradiation.