title: Metal-free and electrocatalytically active nitrogen-doped carbon nanotubes synthesized by coating with polyaniline.
abstract: Nitrogen doping of multi-walled carbon nanotubes (CNTs) was achieved by the carbonization of a polyaniline (PANI) coating. First, the CNTs were partially oxidized with KMnO4 to obtain oxygen-containing functional groups. Depending on the KMnO4 loading, thin layers of birnessite-type MnO2 (10 wt% and 30 wt%) were obtained by subsequent thermal decomposition. CNT-supported MnO2 was then used for the oxidative polymerization of aniline in acidic solution, and the resulting PANI-coated CNTs were finally heated at 550 degrees C and 850 degrees C in inert gas. The samples were characterized by transmission electron microscopy and X-ray photoelectron spectroscopy. A thin layer of carbonized PANI was observed on the CNT surface, and the surface nitrogen concentration of samples prepared from 30% MnO2 was found to amount to 7.6 at% and 3.8 at% after carbonization at 550 degrees C and 850 degrees C, respectively. These CNTs with nitrogen-containing shell were further studied by electrochemical impedance spectroscopy and used as catalysts for the oxygen reduction reaction. The sample synthesized from 30 wt% MnO2 followed by carbonization at 850 degrees C showed the best electrochemical performance indicating efficient nitrogen doping.
authors.affiliation: Laboratory of Industrial Chemistry, Ruhr-University Bochum, 44780, Bochum, Germany.
authors.forename: Chen
authors.initials: C
authors.lastname: Jin
authors.forename: Tharamani Chikka
authors.initials: TC
authors.lastname: Nagaiah
authors.forename: Wei
authors.initials: W
authors.lastname: Xia
authors.forename: Bernd
authors.initials: B
authors.lastname: Spliethoff
authors.forename: Shanshan
authors.initials: S
authors.lastname: Wang
authors.forename: Michael
authors.initials: M
authors.lastname: Bron
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Schuhmann
authors.forename: Martin
authors.initials: M
authors.lastname: Muhler