Structural, optical, and photocatalytic properties of La3+ doped CeO2 nanospheres for enhanced photodegradation of tetracycline

Abstract

This work reports the structural, optical, and photocatalytic properties of Ce1−xLaxO2 nanospheres (x = 0, 0.04, 0.06, 0.08, and 0.10) for the photodegradation of organic pollutants. The Ce1−xLaxO2 samples with particle sizes of ∼ 9–30 nm were prepared by a solution method using polyvinyl pyrrolidone (PVP) as a polymer precursor. The prepared Ce1−xLaxO2 samples were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results of XRD and TEM with selected area electron diffraction (SEAD) show that the prepared Ce1−xLaxO2 nanospheres have a cubic fluorite structure without secondary phase. The XPS shows the presence of oxygen vacancies on the surfaces of all samples. The Ce0.90La0.10O2 sample shows the highest concentration of oxygen vacancies, causing a decrease in Eg, and thus resulting in an enhancement of its photocatalytic activity. The photocatalytic activities of the CeO2 and Ce1−xLaxO2 photocatalysts were studied by the degradation of TC solution under visible light irradiation. Pure CeO2 shows poor photocatalytic activity with about 43 % of TC degraded in 40 min, while Ce1−xLaxO2 exhibits significantly higher photocatalytic efficiency, which increases with La-doping concentration. It is proposed that photogenerated holes are the main active species for photochemical degradation of the TC via Ce0.90La0.10O2 upon irradiation with visible light, while superoxide radicals and hydroxyl radicals are the less active species. Our results indicate that, with excellent photocatalytic performance, the Ce1−xLaxO2 nanospheres can be further developed for photocatalytic applications.