Construction of Nonclassical Type-I Heterojunction for Efficient Photodegrading Tetracycline

Traditional Type-I heterojunctions, the combination of large- and narrow-bandgap semiconductors, possess a long electron transmission path and an electron–hole confinement region, making them not conducive to improving catalytic performance. Hence, few studies about the heterostructure combined with large and narrow bandgap in chemocatalysis were invested, especially in terms of reaction mechanism. Herein, a narrow bandgap (CdS) and a large bandgap (hexagonal boron nitride, h-BN) were selected as the research objects to fabricate h-BN/CdS heterojunction by Joule heating by an ultrafast heating procedure. Density functional theory (DFT) calculations were performed and showed that in the h-BN/CdS heterojunctions photogenerated electrons (e^–) transferred from h-BN to CdS, while the photogenerated holes (h⁺) moved conversely, which is completely different from that of classical Type-I heterojunctions. Thus, a nonclassical Type-I h-BN/CdS heterojunction was successfully constructed, as proved by DFT calculations and experimental verification, which revealed excellent visible light response and photocatalytic degradation ability of tetracycline (TC). The optimized h-BN/CdS heterojunction exhibited a high degradation rate of 84.78% under visible light irradiation. Additionally, the applicability of h-BN/CdS heterojunction was expanded to photodegradation of different water environments. A nonclassical Type-I heterojunction that combined large- and narrow-bandgap materials was proposed, which opened up a new path for efficient photocatalysis in antibiotic wastewater degradation.