Controllable synthesis of nitrogen-doped carbon nanotubes derived from halloysite-templated polyaniline towards nonprecious ORR catalysts

Halloysites were applied as the template to form halloysite/polyaniline core/shell hybrids through an oxidative polymerization route, where the amount of aniline monomer could be adjusted to precisely control the shell thickness of polyaniline. The pyrolysis process was then applied to ensure the carbonization of the polyaniline to form halloysite/nitrogen-doped carbon core/shell hybrids. Finally, halloysites were removed, resulting in the formation of nitrogen-doped carbon nanotube with a uniform morphology and a controlled shell thickness. The shell thickness and pyrolysis temperature of nitrogen-doped carbon nanotubes were optimized to improve the electrocatalytic performance involved in oxygen reduction reaction. The nitrogen-doped carbon nanotubes showed good electrocatalytic activities toward oxygen reduction reaction in 0.1 mol L-1 KOH aqueous solution, making them a promising cathode catalyst for alkaline fuel cell applications.