Solar Degradation of Toxic Colorants in Polluted Water by Thermally Tuned Ceria Nanocrystal-Based Nanofibers

This work demonstrates a facile method for the synthesis of a "green" photocatalyst for efficient solar degradation of toxic colorants in polluted water. CeO2 nanofiber crystals were fabricated by electrospinning and thermal tuning at 500–1000 °C. It was found for the first time that the photocatalytic performance of pure CeO2 was improved by simple thermal tuning. Without incorporating any potentially harmful impurities, the pure CeO2 nanofiber crystals degraded up to 97.6% methylene blue (MB) in 180 min under simulated solar irradiation. Further, the CeO2 nanofiber crystals demonstrated an excellent long-term recycling stability with less than 1% activity fluctuations in 10 cycles. The improved photocatalytic performance was attributed to the small crystal size, clean crystal surface, and plenty of oxygen vacancies of CeO2. SEM and TEM observations showed that the average fiber diameter decreased while the particle size increased with tuning temperature. FTIR revealed that the surface-adsorbed organic moieties decreased with the increase of temperature, making active sites more accessible for photocatalysis. The presence of oxygen vacancies was confirmed by both Raman and XPS, which were critical for the activation of oxygen in photocatalysis. Our pure CeO2 photocatalyst is eco-friendly and inexpensive for large-scale application for the removal of toxic colorants to fulfill environmental sustainability.