Metal-free nitrogen-rich glassy carbon as an electrocatalyst for hydrogen evolution reaction

Abstract A new metal-free nitrogen-rich glassy carbon (MF-NGC) was fabricated from polybenzoxazine through carbonization and KOH chemical activation method. Benzoxazine monomer was synthesized from hydroquinone, urea and paraformaldehyde, followed by ring-opening polymerization to produce nitrogen-rich polybenzoxazine. The obtained polybenzoxazine after carbonization and KOH activation results in the formation of MF-NGC. Chemical structure of the new benzoxazine monomer was confirmed by FTIR and NMR spectroscopy. The amorphous nature of carbon was confirmed by XRD analysis with low degree of graphitization as analyzed by XRD and Raman techniques. SEM images portray MF-NGC containing C, N and O with N content of about 11.3 wt%. BET investigation measures the surface area of MF-NGC to be 166 m2/g with numerous mesopores and few macropores. Furthermore, MF-NGC was thoroughly investigated by relating physicochemical and electrochemical techniques. The doped nitrogen species with interconnected carbon matrix affords rich active sites suitable for HER. MF-NGC exhibits the lowest overpotential of −190 mVRHE and Tafel slope of 55 mV dec−1 in 0.5 M H2SO4 aqueous electrolyte possessing outstanding catalytic activity and excellent stability towards HER.