Hydrothermal synthesis of mesoporous cerium oxide nanoparticles with improved properties by niobium doping

Abstract

Nanostructured materials exhibit remarkable properties, making them promising candidates for effluent treatment applications. The doped compounds can further enhance their efficiency. Herein, cerium and niobium-based nanomaterials were synthesized using an easy hydrothermal method for application in effluent treatment. Materials with different Ce:Nb molar ratios were produced and characterized using various techniques, including X-ray fluorescence, powder X-ray diffraction, adsorption-desorption isotherms of N₂, Raman spectroscopy, electron paramagnetic resonance spectroscopy, thermogravimetric analysis, scanning electron microscopy combined with energy-dispersive X-ray spectroscopy, and UV–Vis diffuse reflectance spectroscopy. The results confirmed the incorporation of niobium into the structures of the materials, which showed mesoporous characteristics, and the Rietveld refinement shows a decrease in lattice parameters, suggesting that niobium replaces some Ce ions in the CeO₂ structure. A higher niobium ratio led to a larger pore diameter but a smaller surface area. Additionally, the materials exhibited absorption in the UV region and a bandgap between 2.75 and 2.85 eV, demonstrating their potential for use in photocatalytic reactions. The materials were tested for oxidation of dye compounds under ultraviolet and visible light, and the results showed a tremendous oxidative potential. The best condition presented 100 % degradation after 60 min of reaction, and after five reaction cycles, it was kept above 90 % removal. Mass spectrometry with electrospray ionization (ESI-MS) spectra and total organic carbon (TOC) rate showed the high oxidation rate of the dye. So, niobium doping in cerium oxide showed an increased catalytic potential, which does not require catalytic support or a semiconductor for photocatalysis reactions.