Surface oxygen vacancy induced solar light activity enhancement of a CdWO₄/Bi₂O₂CO₃ core-shell heterostructure...

A CdWO₄/Bi₂O₂CO₃ core-shell heterostructure photocatalyst was fabricated via a facile two-step hydrothermal process. Flower-like Bi₂O₂CO₃ was synthesized and functioned as the cores on which CdWO₄ nanorods were coated as the shells. Photoluminescence (PL) spectra and electron paramagnetic resonance (EPR) demonstrate that the CdWO₄/Bi₂O₂CO₃ core-shell heterostructure photocatalyst possesses a large amount of oxygen vacancies, which induce defect levels in the band gap and help to broaden light absorption. The photocatalyst exhibits enhanced photocatalytic activity for Rhodamine B (RhB), methylene blue (MB), methyl orange (MO), and colorless contaminant phenol degradation under solar light irradiation. The heterostructured CdWO₄/Bi₂O₂CO₃ core-shell photocatalyst shows drastically enhanced photocatalytic properties compared to the pure CdWO₄ and Bi₂O₂CO₃. This remarkable enhancement is attributed to the following three factors: (1) the presence of oxygen vacancies induces defect levels in the band gap and increases the visible light absorption; (2) intimate interfacial interactions derived from the core-shell heterostructure; and (3) the formation of the n-n junction between the CdWO₄ and Bi₂O₂CO₃. The mechanism is further explored by analyzing its heterostructure and determining the role of active radicals. The construction of high-performance photocatalysts with oxygen vacancies and core-shell heterostructures has great potential for degradation of refractory contaminants in water with solar light irradiation.