N-doped hard carbon nanotubes derived from conjugated microporous polymer for electrocatalytic oxygen reduction reaction

The development of efficient non-metal catalysts (NMC) towards oxygen reduction reaction (ORR) in both acidic and alkaline electrolyte is of great importance for construction of new generation fuel cell. Herein, we demonstrate the fabrication of N-doped hard carbon nanotubes prepared by carbonization of melamine-incorporated nanotube-like conjugated microporous polymers (CMPs), as novel electrocatalysts for efficient ORR. As a kind of metal-free electrocatalyst, the as-prepared carbon nanotubes exhibit superior ORR activity not only in alkaline electrolyte but also in acidic condition. Interestingly, obvious enhancement on the diffusion-limited current density (increased by 1.8 mA cm−2) for the N-doped products in acid solution is observed by comparison with that of carbonized CMPs nanotubes without N-doping. Furthermore the catalysts also show better methanol immunity than that of commercial 20 wt% Pt/C. And only a slight decrease (14 mV negative shift) in half-wave potential is detected after 5000 cycles in 0.1 M KOH, indicating an ideal electrochemical stability which makes the N-doped hard carbon nanotubes promising candidate as an efficient electrocatalyst for ORR, by combination with their desirable electrocatalytic ORR activity, methanol tolerance and stability.