Coupled Cu doping and Z-scheme heterojunction for synergistically enhanced tetracycline photodegradation

Semiconductor-based photocatalysis by utilizing solar energy for sustainable organic pollutant elimination has been a promising tactic to alleviate environmental issues. Nevertheless, the development of robust and efficient photocatalysts to degrade organic pollutants still faces major challenges because of insufficient charge separation. Here we design and fabricate a heterojunction consisting of copper, carbon-modified TiO2, and sulfur-doped g-C3N4 nanosheets (i.e., S-C3N4/Cu/C-TiO2). The heterostructure affords a remarkable synergistic photocatalysis for tetracycline hydrochloride degradation, achieving an 82.6% removal efficiency within 30 min under visible light irradiation, about 15.4 and 7.3 times higher than that of S-C3N4 and C-TiO2, respectively. The superior performance is attributed to the synergy between Cu doping and the Z-scheme heterojunction, which not only enhances the interfacial electric field effect, facilitating charge separation, but also boosts the redox capability. The charge carrier transfer between Cu/C-TiO2 and S-C3N4 follows a Z-scheme, as verified by trapping experiments, electron spin-resonance spectroscopy, and density functional theory calculations. Furthermore, the tetracycline hydrochloride degradation pathways are enunciated by liquid chromatograph mass spectrometry analysis. This work provides an effective approach for constructing high-performance photocatalysts that have potential in environmental remediation.