Freeze-drying synthesis of O,N–CeF3 with enhanced photocatalytic oxygen evolution

Drying methods have been verified to have a considerable impact on photocatalytic efficiency via altering surface area. In this study, the preparations of O,N–CeF3 under identical conditions using the vacuum freezing method and the oven method are compared. Surface hydroxyl, as opposed to adsorbed oxygen in CeF3–O, is the main component of O faults on the surface of CeF3–V. Small particle size and the doping atom defects of CeF3–V allow for more efficient separation and faster migration of photogenerated charge carriers. CeF3–V has an oxygen evolution rate of up to 1.4138 mmol/(g·h) and an apparent quantum yield of 90.90% at 550 nm. Energy tails are produced as a result of the doping O and N changing the intrinsic band structures. CeF3–V shows a secondary conduction band potential that is sufficient for satisfying the minimal water oxidation potential simultaneously. These elucidate that defects in the states of doping O and N significantly influence CeF3 energy levels. Focusing on how the drying process affects the band structure and encourages carriers' separation via defects is valuable, which affects how well the photocatalysis works.