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

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.