Synthesis of cobalt-impregnated carbon composite derived from a renewable resource: Characterization and catalytic performance evaluation

A novel nitrogen-doped biochar embedded with cobalt (Co-NB) was fabricated via pyrolysis of glucose pretreated with melamine (N donor) and Co(II). The Co-NB showed high catalytic capability by converting p-nitrophenol (PNP) into p-aminophenol (PAP) by NaBH₄. The analyses of FE-SEM, TEM, BET, XRD, Raman, and X-ray photoelectron spectroscopy XPS of the Co-NB showed hierarchical porous structure (BET 326.5 m² g^{− 1} and pore volume: 0.2403 cm³ g^{− 1}) with well-dispersed Co nanoparticles (20–60 nm) on the N-doped graphitic biochar surface. The Co-NB showed higher PNP reduction capability compared to the Co-biochar without N-doping, achieving 94.3% removal within 4 min at 0.24 g L^{− 1} catalyst dose and initial concentration of 0.35 mM PNP. Further conversion experiments under varying environmental conditions (e.g., NaBH₄ concentration (7.5–30 mM), biochar dosage (0.12–1.0 g L^{− 1}), initial PNP concentration (0.08–0.17 mM)) were conducted in batch mode. The reusability of Co-NB was validated by the repetitive conversion experiments (5 cycles). The overall results demonstrated biochar potential as catalysts for environmental applications if properly designed.