Tailored defects for metal-free nitrogen-doped carbons toward efficient oxygen reduction reaction using tripolycyanamide-based microporous polymer as precursor

Abstract

Fabrication of metal-free carbon electrocatalysts with low-cost, high-performance and outstanding stability is great important for realizing the widespread application of fuel cells and metal-air batteries. Herein, we report a simple approach for the preparation of N-doped and defects-rich metal-free carbon (NDC) catalysts via carbonization of tripolycyanamide-based microporous polymer (TCAMP) in O2/N2 atmosphere, where the N-rich TCAMP was synthesized by a simple two-step polymerization process using the low-cost tripolycyanamide monomer (TCA) and paraformaldehyde as monomer. Raman spectra and X-ray diffraction (XRD) characterization indicated that the defects in NDCs’ carbon skeleton increased with the increasing pyrolysis temperature. Electrochemical studies showed that NDCs pyrolyzed in O2/N2 atmosphere presented a higher efficient oxygen reduction reaction (ORR) activity than its counterpart pyrolyzed in Ar atmosphere. The NDCs obtained at the pyrolysis temperature of 900 °C (NDC-900) presented an impressive oxygen reduction reaction (ORR) activity with a high half-wave potential of 0.853 V, owing to its large surface area (1808 m2 g−1), hierarchical meso‑micro pores and high active sites from the synergistic effect of N-doping and defects. Moreover, as-synthesized NDC-900 displayed a much better stability and methanol tolerance than commercial Pt/C catalyst. This work thus gives insights into fabricating promising alternative carbon catalysts for ORR process via one-step pyrolysis process using low-cost raw material.