Study of nitrogen-doped carbon nanomaterials by bomb calorimetry

Nitrogen-doped carbon nanotubes (N-doped CNTs) and nitrogen-doped carbon nanoflakes (N-doped CNFs), which are promising materials for energy storage devices, were investigated by adiabatic bomb calorimetry method to determine their enthalpies of combustion (ΔcH0298) and of formation (ΔfH0298). All materials were characterized by elemental analysis, transmission and scanning electron microscopy, X-ray photoelectron, Raman spectroscopy as well as thermal analysis. The relationships between composition, nitrogen content and structure were studied. All ΔfH0298 values of the N-doped CNTs and CNFs were found to be negative and to decrease with the increase in nitrogen content. The value of ΔfH0298 of the N-doped CNTs changed from -(0.79 ± 0.01) to -(74.08 ± 0.15) kJ/mol with the increase in nitrogen content from 1.54 to 2.52 wt. % and that of N-doped CNFs changed from -(59.49 ± 0.30) to -(126.84 ± 1.16) kJ/mol with the increase in nitrogen content from 7.07 to 11.25 wt. %. The enthalpy of formation of carbon nanoflakes was -(29.78 ± 0.58) kJ/mol which is higher than that for N-doped CNFs.