Low-Crystallized Carbon as an Electron Mediator in g-C3N4/C/TiO2 for Enhancing Photocatalytic Degradation of Antibiotics

Photodegradation of antibiotics based on photocatalytic semiconductors is a promising option to alleviate water pollution. Despite its limitations, TiO2-based photocatalysts are still the most widely studied materials for pollutant degradation. In this work, a pomegranate-like g-C3N4/C/TiO2nano-heterojunction was constructed using the hydrothermal–calcination method, consisting of interconnected small crystals with a dense structure and closely contacted interface. Low-crystallized carbon filled the gap between TiO2and g-C3N4, forming a large interface. The local in-plane heterostructures generated by C/g-C3N4are further improved for carrier transport. As expected, the optimal sample calcined at 300 °C (GTC-300) efficiently eliminated tetracycline hydrochloride (TC-HCl, 20 mg L−1), achieving a removal rate of up to 92.9% within 40 min under full-spectrum irradiation and 87.8% within 60 min under the visible spectrum (λ > 400 nm). The electron mediator, low-crystallized carbon, successfully promoted the formation of new internal electric fields via the widespread heterojunction interface, which accelerated the separation and migration of photogenerated carriers between g-C3N4and TiO2. These results confirm that the g-C3N4/C/TiO2nano-heterojunction exhibited outstanding photodegradation performance of TC-HCl. The electron mediator shows great potential in promoting carrier transfer and enhancing photocatalytic performance of heterogeneous photocatalysts in water treatment.