MOF-derived carbon nanotubes as an highly active electrocatalyst for oxygen reduction reaction in alkaline and acidic media

Abstract

The high-activity and low-cost electrocatalyst for oxygen reduction reaction (ORR) is important for proton exchange membrane fuel cells (PEMFCs). In this work, nitrogen-doped carbon nanotubes (Fe/N@CNT) prepared by pyrolyzing metal-organic skeleton materials Fe-ZIF-8 and g-C3N4 were used as electrocatalyst for oxygen reduction reaction. During the pyrolysis process, a large amount of nitrogen-containing gas is released which anchors Fe2+ ions in ZIF-8, forming an ORR catalytically active center (Fe-Nx). The as-synthesized Fe/N@CNT is a porous carbon material with high specific surface area (821.9 m2 g−1). The optimal Fe/N@CNT exhibits excellent ORR electrocatalytic activity with high half-wave potential (E1/2) of 0.892 V vs. RHE, which was 34 mV higher than that of commercial Pt/C (0.858 V vs. RHE) in 0.1 M KOH; E1/2 of Fe/N@CNT in 0.1 M HClO4 was 0.79 V vs. RHE, which was close to that of commercial Pt/C (0.88 V vs. RHE). Additionally, Fe/N@CNT shows long-term stability both in alkaline and acidic medium. The excellent electrocatalytic activity of Fe/N@CNT attributed to the rich micropores and mesopores structure and large specific surface area. This work offers a new approach to design and synthesize catalysts for ORR.