Nitrogen-doped hollow carbon polyhedron derived from salt-encapsulated ZIF-8 for efficient oxygen reduction reaction

Abstract

The sluggish kinetics of oxygen reduction reaction (ORR) seriously restrains the practical implementation of fuel cells and metal-air batteries (MABs). While, Pt-based catalysts are well proven to be effective for the ORR process, they are rather expensive. Therefore, it is critical to developing low-cost and advanced catalysts with a rationally designed structure and abundant reactive sites as alternatives for Pt-based catalysts. Herein, nitrogen-doped hollow carbon polyhedrons (NHCP) have been fabricated by directly pyrolyzing ZIF-8, templated by NaCl. Benefiting from their hollow porous structure, large surface area, high graphitization degree and desired nitrogen bonding type, the as-synthesized NHCP exhibits exceptional ORR electrocatalytic activity with a half-wave potential (E1/2) of 0.86 V, high selectivity and outstanding long-term stability, exceeding most reported nitrogen-doped metal-free carbon electrocatalysts. Furthermore, the assembled Zn-air battery with NHCP cathode delivers a peak power density of 272 mW cm−2, a specific capacity of 740 mAh g−1 and an operation period of 160 h. This contribution provides a new avenue for designing high-performance electrocatalysts for ORR.