An experimental and theoretical approach to organic functionalization of carbon nanofibers using fresh neem leaves

Carbon nanofibers (CNF) are state-of-the-art materials that have been actively explored for several applications. In this study, we have given organic functionalization treatment to CNF using fresh neem leaves (FNL) following a simple ultrasonication methodology. The effects of dispersion treatment (using Triton X-100) on the functionalization of CNF are also investigated. The samples are characterized via FESEM, EDX, XPS, XRD, CHNS, XRF, and FTIR studies. The FESEM and XRD analyses confirm that the CNF morphology remains intact upon organic treatment. The EDX, XRF, CHNS, and FTIR studies reveal the functionalization of CNF with several heteroatoms (N: 7.41 at.%, O: 4.38 at.%, S: 0.027 at.%, P: 0.42 at.%, etc.), and nutrients present in the FNL. The electrocatalytic activity of the modified CNF is tested via cyclic voltammetry and linear sweep voltammetry studies in 0.1 M KOH electrolyte. The onset potential is −0.018 V, the half-wave potential is −0.35 V, and the limiting current density is 3.26 mA/cm2 for this sample. The oxygen reduction at FNL modified-CNF occurs via a four-electron pathway (n = 3.76) in the alkaline medium. The direct functionalization treatment of CNF is more effective for the observed intermolecular charge interactions between CNF and the FNL extract, however, the Triton X-100 coating on CNF acts as a mask to suppress these interactions. The simulation studies reveal that the upper and edge sites in the cup-stacked CNF are most active for ORR catalysis. It includes a detailed interaction study of the CNF-alanine molecule, which could be beneficial for designing novel biosensors.