Carbon nitride S-scheme homojunction featuring strong interfacial electric field for efficient photodegradation.

The construction of highly efficient S-scheme homojunction relies on precise regulation of the material's energy band structure and rational design of favorable charge transfer interfaces. In this study, the charge behavior of carbon nitride (CN) is modulated by an evaporation-induced self-assembly precursor polymerization method. Experimental results and DFT calculations demonstrate that both the intrinsic bandgap and surface electronic properties of the material are effectively tuned, successfully establishing a tightly contacted homojunction interface driven by van der Waals forces and introducing an interfacial electric field (IEF). The resulting homojunction catalyst, composed of CN nanoparticles and CN nanosheets, exhibits a pronounced S-scheme carrier separation mechanism, which significantly enhances the separation and migration efficiency of photogenerated charge carriers (proved by PL/TRPL, EIS, PCR, SPV and TPV). Consequently, the homojunction catalyst achieves complete removal of tetracycline (TC) within 15 min, with a rate constant of 0.1969 min-1, which is 1.72 and 6.61 times higher than those of single component. Moreover, it also shows excellent adaptability and stability over a wide pH range, in different water matrices, and against various pollutant systems. Theoretical calculation and actual toxicity assessment further confirm the environmental safety of the degradation products. This work provides an efficient strategy for optimizing the structural properties of g-C3N4 and holds great promise for applications in the field of environmental water remediation.