Carboxylic acid-functionalized cadmium sulfide/graphitic carbon nitride composite photocatalyst with well-combined interface for sulfamethazine degradation

The carboxylic acid-functionalized cadmium sulfide/graphitic carbon nitride (CdS-TGA/g-C3N4) isotype heterojunction was prepared by thermal copolymerization of CdS-TGA/urea, which was formed via the interaction between COO− groups on CdS-TGA NPs and -NH2/-NH groups on urea. It was proposed that the well-developed combined interface between CdS-TGA and g-C3N4 was formed in CdS-TGA/g-C3N4 and consequently improved the stability and separation of the photo-generated charge carriers. As a result, the CdS-TGA/g-C3N4 exhibited significantly enhanced activity for the visible-light photocatalytic degradation of sulfamethazine (SM2) as compared to CdS/g-C3N4. The O2− was found to be the dominant active species for SM2 decomposition and the possible photocatalytic degradation pathway of SM2 over CdS-TGA/g-C3N4 was through sulfonate elimination. This work demonstrated rational design and preparation of CdS-based heterojunction composites via construction of well-combined interface, which could open up a new way for the development of efficient and stable visible-light photocatalysts.