Breaking new grounds: Solid-state synthesis of TiO2-La2O3-CuO nanocomposites for degrading brilliant green dye under visible light

Environmental pollution, particularly from industrial dyes and chemicals, poses a significant threat to ecosystems and human health. Traditional pollution mitigation methods are often inefficient and costly. Photocatalysis has emerged as a promising solution for degrading pollutants using light energy. Titanium dioxide (TiO2) is a widely studied photocatalyst due to its stability, non-toxicity, and strong oxidative power. However, its efficiency is limited by a wide bandgap, restricting absorption to the UV region, and rapid electron-hole recombination. To address these limitations, doping TiO2 with materials (La2O3 and CuO) can enhance its photocatalytic activity under visible light. This study investigates the enhancement of TiO2 nanocomposites by incorporating La2O3 and CuO. X-ray diffraction (XRD) revealed that the nanocomposites retained the TiO2 anatase and rutile phases with their improved crystallinity. Scanning electron microscopy (SEM) displayed spherical nanoparticles forming agglomerates, typically due to high surface energy. Energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) confirmed the presence of La and Cu in the TiO2 matrix. Fourier-transform infrared (FTIR) spectroscopy identified characteristic vibrational modes of Ti-O, La-O, and Cu-O bonds, suggesting strong interactions between dopants and TiO2 lattice. Ultraviolet-visible (UV-vis) spectroscopy showed a red shift in absorption spectra with La2O3 and CuO addition, reducing the bandgap energy from 3.23 eV (pure TiO2) to 2.27 eV for the TiO2-0.1La2O3-0.2CuO composite. Photoluminescence (PL) spectroscopy indicated improved charge separation and reduced electron-hole recombination rates in the synthesized nanocomposites. Photocatalytic performance was evaluated by degrading brilliant green (BG) dye under visible light. The TiO2-0.1La2O3-0.2CuO (TLC0.2) nanocomposite achieved the highest dye degradation of over 95% after 204 min under optimal conditions (Co = 17 mg/L and 1 g/L). Adding the inorganic agent Na2SO4 to this process significantly enhanced the photocatalytic activity, increasing degradation from 56% to 95% after 180 min of visible light irradiation. TLC0.2 exhibited a high stability of dye degradation efficiency after six consecutive photocatalysis cycles. La2O3 and CuO doping significantly enhance TiO2 nanocomposites' crystalline structure, morphology, optical property, and photocatalytic efficiency. TLC0.2 has a potential use for environmental remediation and solar energy conversion.