Furan and Pyran Functional Groups Driven the Surface of Nitrogen-Doped Nanofiber Sponges

Abstract

"Highly surface oxidized, nitrogen?doped, and nitrogen functionalized carbon nanotube sponge (N?CFS) were produced at 1020?°C using two sprayers approach in an aerosol?assisted chemical vapor deposition (AACVD) experiment. The structure of N?CFS consisted of entangled and corrugated carbon nanofibers of ?200?nm diameter, also showing junctions and knots. TEM characterizations revealed that the carbon nanofiber exhibits stacked graphitic layers in a transversal way with positive curvature. Superficial chemical analysis by XPS showed that the N?CFSs contain an atomic concentration of oxygen and nitrogen of 9.2% and 2.9%, respectively. The high?resolution XPS scans deconvolution?analysis revealed high percentages for C?O bonds, pyrrolic nitrogen doping, NH3 functionalization, and Si?C interactions. The cyclic voltammetry measurements did not display a redox process despite the high oxygen concentration at the surface. Hydrophobic functional groups containing C?O bonds do not participate in a redox process (furan, pyran, epoxy, methoxy, ethoxy, among others) could mostly determine the electroactivity of N?CFS. Based on density functional theory calculations, we determine that the furans transfer a high amount of electron and promote a positive curvature in thin carbon nanotubes. Graphitic materials with furans, pyrans, and epoxy functional groups could be used as an anode in lithium?ion batteries."