Nitrogen-Doped Carbon Nanotubes Prepared at Different Temperatures for Oxygen Reduction Reaction

Abstract

The nitrogen-doped carbon nanotubes (N-CNTs) were synthesized by chemical vapor deposition using ethanediamine as a precursor and ferrocene as a growth catalyst under the reaction temperatures of 800°C, 850°C, 900°C and 950°C, respectively. The doped nitrogen aggregated within the bamboo joints of CNTs, and the reaction temperature influenced the amount and type of nitrogen doped into CNTs. The best catalytic activity toward oxygen reduction reaction (ORR) in an alkaline medium was obtained with the N-CNTs prepared at 800°C due to the largest amount of nitrogen being doped into CNTs mainly in the form of pyridinic type. However, the reaction temperature of 900°C is so close to the crystal transformation temperature of iron due to the use of ferrocene that nitrogen would be difficult to be doped into CNTs. Accordingly, the presence of least amount of pyridinic type nitrogen accounted for the poorest ORR activity of N-CNTs prepared at 900°C.