Tunable Synthesis of Covalently Coupled G-C₃N₄/RGO Nanohybrid and N-Doped RGO via Scalable Precursor Composition...

The development of efficient, scalable metal-free catalysts is vital for sustainable chemical processes. Here, we report a tunable one-step thermal synthesis of 2D/2D graphitic carbon nitride/reduced graphene oxide (g-C₃N₄/RGO) nanohybrids and nitrogen-doped RGO (N-RGO) by varying the urea-to-GO mass ratio. Urea-rich mixtures yield RGO-intercalated g-C₃N₄, while GO-rich compositions produce N-RGO. GO promotes amine condensation and acts as a structural scaffold for g-C₃N₄ growth, while urea serves as a g-C₃N₄ precursor, nitrogen dopant, and reducing agent. XRD, FTIR, and XPS analyses confirm sheet exfoliation and the formation of interfacial CN covalent bonds, evidencing strong coupling between g-C₃N₄ and RGO. BET and electrochemical impedance results reveal that catalytic enhancement arises primarily from interfacial electronic coupling and accelerated charge transfer rather than surface area effects. The g-C₃N₄/RGO-60% composite exhibits optimal coupling and achieves 100% conversion of 4-nitrophenol to 4-aminophenol within 3 minutes (k = 1.33 min^-1), outperforming pristine RGO and g-C₃N₄ by 66- and 33-fold, respectively. N-RGO exhibits high efficiency (k = 0.94 min^-1), attributed to enhanced catalytic sites from nitrogen doping. This scalable, low-cost method enables precise tuning of structureproperty relationships, offering high-performance metal-free catalysts for both dark and light-driven environmental remediation and sustainable organic transformations.