Control of nitrogen content and its effects on the electrochemical behavior of nitrogen-doped carbon nanofibers

Nitrogen-doped carbon nanofibers (N-CNFs) with different nitrogen contents were synthesized from vaporized acetonitrile as a simultaneous carbon and nitrogen source via the chemical vapor deposition method. N-CNF synthesis was conducted at 640 °C for 2 h, and the ratio of nitrogen and hydrogen mixture as reactant gas was adjusted to control the nitrogen content in the N-CNFs. The amount of hydrogen in the reactant gas was varied in the range from 0 to 40 mL min^-1. The physical and electrochemical properties of the N-CNFs were characterized. The content of introduced nitrogen decreased with the ratio of supplied hydrogen, as opposed to the growth yield of the N-CNFs. Additionally, the nitrogen content and chemical states of the N-CNFs were examined and compared to reveal their correlations with the electrochemical behavior. The N-CNFs were found to have a noticeable electrochemical behavior such as capacitance and oxygen reduction reaction activity that was determined by the total nitrogen contents, especially those of pyridinic-nitrogen.