Enhanced photocatalytic activity and mechanism of CeO₂ hollow spheres for tetracycline degradation

Recently, researchers have focused on designing and fabricating highly efficient catalysts for photocatalytic organic pollutant removal. Herein, CeO₂ hollow spheres were prepared through a simple template method followed by calcination at different temperatures for the tetracycline (TC) degradation under simulated solar light illumination. With a calcination temperature ranging from 400 to 800 °C, the as-prepared CeO₂ hollow structure annealed at 600 °C (C₆₀₀) exhibited the best degradation performance with a degradation rate constant of 0.066 min⁻¹, which was about six and five times higher than those of the uncalcined sample (C₀) and the sample calcined at 800 °C (C₈₀₀), respectively. Moreover, sample C₆₀₀ was also superior to the CeO₂ solid particle photocatalyst. The characterisation results showed that the improved photocatalytic performance was mainly ascribed to the synergistic effect of large specific surface areas, high crystallisation and excellent light scattering ability. Furthermore, the results of active species trapping experiments demonstrated that the superoxide anion (•O₂⁻) radical and hole (h⁺) played dominant roles in TC degradation. Subsequently, the possible TC degradation pathways and photocatalytic mechanism of CeO₂ hollow spheres were proposed on the basis of high-performance liquid chromatography–mass spectrometry analysis, main active species and band edge positions of CeO₂. The results of this study provide a basis for designing and exploring hollow structure catalysts for energy conversion and environmental remediation.