The slow kinetics of the oxygen reduction reaction (ORR) remains a primary bottleneck for the efficiency of fuel cells and metal-air batteries. In this study, Nitrogen-doped carbon porous frameworks (N-CFs) were synthesized via the pyrolysis of nitrogen-doped carbon dots (N-CQDs). The N-CQDs were prepared using pyrolysis of urea and glucose. Subsequent post-thermal annealing at 800°C transformed the N-CQDs into N-CPFs. X-ray diffraction (XRD) and Raman spectroscopy confirmed the successful evolution from a semi-crystalline intermediate into a disordered, turbostratic carbon porous with a high density of defects (ID/IG ratio), which serve as critical active sites. Scanning electron microscopy (SEM) revealed a significant morphological shift from discrete 0D quasi-spherical nanoparticles to sponge-like 3D architecture featuring hierarchical porosity. Electrochemical evaluations in an O₂-saturated 0.1 M KOH solution demonstrated that the N-CF exhibits superior electrocatalytic activity compared to its N-CQD precursors, achieving higher limiting current density of -2.9 mA/cm², a more positive onset potential, and low charge transfer resistance. This enhanced performance is attributed to the synergistic effect of the 3D continuous conductive network, which facilitates rapid electron transport, and the hierarchical porosity that optimizes the mass transport of oxygen molecules to the active nitrogen sites significantly higher limiting current density of -2.9 mA/cm² and a more positive onset potential.
