Nitrogen-doped carbon nanotubes as catalysts for oxygen reduction reaction

► The aligned nitrogen-doped carbon nanotubes (NCNT) were synthesized. ► NCNT doped from melamine and urea was named M-NCNT and U-NCNT, respectively. ► M-NCNT has higher nitrogen content and more defects than U-NCNT. ► M-NCNT has shown better ORR performance than U-NCNT.