Design and Performance Enhancement of Cobalt-Encapsulated Nitrogen-Doped Carbon Nanofiber Electrocatalyst through Ionic Liquid Modification for Efficient Oxygen Reduction

Abstract

The design of platinum-group-metal-free (PGM-free) electrocatalysts with appreciable activity and durability toward the oxygen reduction reaction (ORR) in acidic environments is a big challenge. Here, we report an efficient oxygen reduction activity of a Co-encapsulated nitrogen-doped carbon with nanofiber networks and its ionic liquid-modified interface in an acidic medium. The robust structure of the nanofibers embedded on a rigid framework derived from a zeolitic imidazole framework (ZIF-67) delivers promising activity and durability to the catalyst comparable to the state-of-the-art Pt/C. The ionic-liquid-modified catalyst shows a half-wave potential of 0.71 V vs RHE in oxygen-saturated 0.5 M H2SO4 along with activity reduction by only 11 mV (E1/2) after 5000 cycles of the accelerated durability test. The catalyst also retains 71% of its original current during the short-term durability test. Furthermore, the electron transfer number and H2O2 yield of the catalyst during the ORR approaches 3.88–3.90 and 5.9–4.8% in the potential range 0.4–0.7 V vs RHE. The ORR performance of the ionic-liquid-modified catalyst is superior among all ionic liquid-based non-PGM catalysts reported so far in acidic media.