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.