Synthesis and application of type-II heterojunctions based on CdS and g-C3N5 for efficient photocatalytic degradation of antibiotics

Abstract

Constructing heterostructures is an effective approach to improving the photocatalytic activity of CdS. In this work, a type-II heterojunction was constructed between n-type CdS and n-type g-C₃N₅via a solvothermal method. SEM and TEM results showed that the sample CdS/g-C₃N₅ heterostructure was a flower-like structure, and its specific surface area can reach 27.3 m² g⁻¹. PL results confirmed that the sample CdS/g-C₃N₅ heterostructure had a low recombination rate of electron–hole pairs. Transient photocurrent responses and Nyquist plots revealed that the promoted separation and prolonged retention time of photoexcited carriers can improve the photocatalytic activity of the CdS/g-C₃N₅ heterostructure. Benefitting from the type-II heterojunction of CdS/g-C₃N₅ composites, the lower VB potential made it more efficient to oxidize tetracycline hydrochloride (TCH) to CO₂ and H₂O. The degradation rate of TCH can reach 88.4% within 50 min, and the sample CdS/g-C₃N₅ heterostructure had good photocatalytic stability after five cycles. Furthermore, the photocatalytic mechanism and the possible degradation pathway of the sample CdS/g-C₃N₅ heterostructure were also elaborated.