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

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.