High-performance atomic Co/N co-doped porous carbon catalysts derived from Co-doped metal-organic frameworks for oxygen reduction.

ABSTRACT

Improving the activity and durability of carbon-based catalysts is a key challenge for their application in fuel cells. Herein, we report a highly active and durable Co/N co-doped carbon (CoNC) catalyst prepared via pyrolysis of Co-doped zeolitic-imidazolate framework-8 (ZIF-8), which was synthesized by controlling the feeding sequence to enable Co to replace Zn in the metal-organic framework (MOF). The catalyst exhibited excellent oxygen reduction reaction (ORR) performance, while the half-wave potential decreased by only 8 mV after 5,000 accelerated stress test (AST) cycles in an acidic solution. Furthermore, the catalyst exhibited satisfactory cathodic catalytic performance when utilized in a hydrogen/oxygen single proton exchange membrane (PEM) fuel cell and a Zn-air battery, yielding maximum power densities of 530 and 164 mW cm-2, respectively. X-ray absorption spectroscopy (XAS) and high-angle annular dark field-scanning transmission electron microscopy (HAAD-STEM) analyses revealed that Co was present in the catalyst as single atoms coordinated with N to form Co-N moieties, which results in the high catalytic performance. These results show that the reported catalyst is a promising material for inclusion into future fuel cell designs.