Effects of nitrogen-doping on the microstructure, bonding and electrochemical activity of carbon nanotubes

Vertically aligned carbon nanotubes produced with in-situ doping of nitrogen (CN_x NTs) during chemical vapor deposition exhibit unique structural and electrochemical properties, which are strongly correlated with their nitrogen (N) doping level. In this work, the effects of N-doping on CN_x NTs have been systematically investigated via microstructure and bonding studies, electron-transfer (ET) behaviors, and subsequent electrochemical deposition of catalyst. The CN_x NTs doped with an optimal N level, while showing a nearly reversible ET behavior, in fact exhibit uniform and high density of surface defects. These surface defects are desirable for further modification and/or nucleation of catalytic particles on the surface of CN_x NTs to form a composite electrode for electrochemical energy device applications such as fuel cells and capacitors.