Photocatalytic and magnetic properties of loosened ceria hollow microspheres synthesized by a single-step hydrothermal method

Loosened CeO₂ hollow microspheres with 0.5–1 μm in diameter have been successfully synthesized by a single-step hydrothermal method using Ce(NO₃)·6H₂O as cerium, urea as precipitant, HNO₃ as mineralizer, and polyvinyl pyrrolidone as complexant at 200 °C for different time periods. X-ray diffraction inferred that Ce(OH)CO₃ was gradually transformed to CeO₂ with increasing reaction time from 12 to 60 h, and no Ce(OH)CO₃ was detected but CeO₂ when the reaction time was 60 h. XPS and UV–Vis absorption spectra analysis indicated that the as-synthesized CeO₂ contained a large number of Ce³⁺ in their surface. M–H curve for the loosened CeO₂ hollow microspheres showed an excellent ferromagnetic behavior at room-temperature, which can be attributed to the presence of Ce³⁺ ions. The BET surface area of the catalyst was confirmed to be 83.83 m² g⁻¹ synthesized at 200 °C for 60 h. Correspondingly, its pore width distribution was 6.5 nm. The photocatalytic activities of the ceria were evaluated by the photodegradation of methyl orange under UV light irradiation. Not only the presence of Ce³⁺ ions, but the high surface area led to the excellent photocatalytic performance of the loosened CeO₂ hollow microspheres.