Cooperative coupling strategy for constructing 0D/2D carbon nitride composites with strengthened chemical interaction for enhanced photocatalytic applications

It is difficult for hydrophobic g-C3N4 to construct tight heterogeneous connection with hydrophilic carbon dots (CDs), resulting in deficient charge transfer and restricted interfacial attachment between two components. Doping is an efficient strategy to firmly strengthen the hybridization of g-C3N4/CDs composites by inducing robust π–π conjugates or covalent chemical bonds for strong CDs anchoring to g-C3N4. In this work, a novel CDs anchored and S, Cl co-doped carbon nitride (CSCl-C3N4) nanosheet is rationally designed and successfully fabricated for strong interfacial connection of g-C3N4/CDs. During the formation process, chlorine atoms are doped within the CDs and C-Cl covalent bond is detected. The strong interaction anchors CDs on g-C3N4 and endows heterojunctions more compact connection. Systematic analyses demonstrate that CSCl-C3N4 exhibits remarkably enhanced photocatalytic performance for water splitting. Loading 0.5 wt% CDs to S, Cl co-doped C3N4 achieves the optimal photocatalytic activity among a series of samples (192.49 μmol∙h−1), as evidenced by 25 times that of pristine C3N4 for generating hydrogen. Furthermore, the composite also exhibits considerable photocatalytic activity for photodegradation of tetracycline, in which the degradation rate is 15.3 times that of pristine C3N4. Density functional theory calculations and experimental results are employed to investigate the doping positions of heteroatoms within composites. ∙O2− was verified for predominating during photodegradation process to remove tetracycline by radical scavenge experiments. Based on the significant performance of CSCl-C3N4, the possible mechanism of photocatalytic reactions is put forward. The study provides a novel perspective for modifying nanostructures and constructing heterogeneous interfaces with compact connection via combining anchoring of CDs and doping strategies. The newly fabricated CSCl-C3N4 is a considerable photocatalyst in multifunctional applications for solar energy conversion and pollution abatement.