ZIF-8@ZIF-67–derived ZnCo2O4@nitrogen–doped carbon/carbon nanotubes wrapped by a carbon layer: a stable oxygen reduction catalyst with a competitive strength in acid media

Owing to the sluggish reaction kinetics and poor stability of cathodic catalysts for oxygen reduction reaction (ORR) in acidic media, the development of highly active and acid-stable ORR catalysts is of great practical significance. Herein, the prepared [email protected] material, polyvinylpyrrolidone (PVP), and expanded graphite (EG) are used as precursors to prepare the ZnCo2O4@nitrogen-doped carbon-carbon nanotubes wrapped by a PVP-derived thin carbon layer anchored on the EG (ZnCo2O4@[email protected]/EG) as ORR catalysts. ZnCo2O4@[email protected]/EG-10 (weight ratio of [email protected] to EG = 10) has an onset potential of 0.689 V (vs. SCE), which is comparable with that of commercial Pt/C (0.706 V) in the acid electrolyte. After acid pickling, the spinel ZnCo2O4 as the core is stably and uniformly encapsulated by the NC-CNT skeleton and can fully use the highly active Co2+ sites to boost the 4e– ORR process with a strong methanol resistance. ZnCo2O4@[email protected]/EG-10 shows strong stability and methanol tolerance (a decline of 3.21%) after 3600 s, which are better than those of commercial Pt/C (29 mV and 4.06%). The ORR durability is attributed to the PCL shell that avoids the corrosion of active ZnCo2O4 and N-species. Therefore, it provides a new idea for designing a spinel-based ZIF derivative as stable ORR catalysts in acid media.