Single-phase cerium oxide nanospheres: An efficient photocatalyst for the abatement of rhodamine B dye

Abstract

Single-phase mesoporous CeO₂ nanospheres were synthesized by template-free hydrothermal approach by the synthesis of CeCO₃OH precursor combined with the calcination at 350 °C for 3.0 h. Precursor and calcined products were characterized by XRD, TGA, FESEM, EDX, TEM, N₂ adsorption–desorption and pore size distribution analysis, UV-vis diffuse reflectance (UV-vis DRS), and photoluminescence (PL) analysis. The morphologies of CeO₂ nanospheres were controlled via the optimization of urea concentration during the synthesis. Calcined CeO₂ exhibited excellent photocatalytic activity of rhodamine B (RhB) dye degradation under UV-visible irradiation and mild acidic condition. Scavenger test analysis was used to confirm that the hydroxyl radicals, superoxide radicals, and photogenerated holes are the active photoinduced species of RhB degradation. A comparative study of PL intensity, dye adsorption, and zeta potential measurement revealed the efficient dye adsorption over different CeO₂ photocatalysts. The RhB degradation rate constant has been found to raise linearly with increase of the surface properties. Repeatability test analysis proved the higher catalytic stability of CeO₂ nanospheres without any noticeable loss of activity. Mass spectroscopy and ion chromatography analyses were used to detect the intermediate by-product formation. Finally, based on the results of intermediate detection, possible degradation pathways were also proposed including radical reactions, ring opening, and de-nitrification.