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 a solution containing ethanediamine and ferrocene with the four selected reacting temperatures of 800 ºC, 850 ºC, 900 ºC and 950 ºC. The temperature-dependent morphologies, microstructures, compositions and electrocatalytic activities of the CNTs were examined by SEM, TEM, XPS, Raman and electrochemical measurements. The excellent catalytic activity toward oxygen reduction reaction (ORR) in sodium hydroxide solutions was obtained with the N-CNTs prepared at 800 ºC due to the largest amount of nitrogen being doped into CNTs mainly in the form of pyridinic type nitrogen, while poorer with the N-CNTs prepared at 900 ºC as it is close to the crystal phase transformation temperature of iron. The yield of the N-CNTs increased with the increase of temperature. The growth of N-CNTs was affected by the amounts of nitrogen aggregated within the bamboo joints.