Nanosheet‐Assembled Hierarchical Carbon Nanoframeworks Bearing a Multiactive Center for Oxygen Reduction Reaction

Abstract

AbstractDesigning noble metal‐free electrocatalysts with novel structure and high performance for the oxygen reduction reaction (ORR) has been long pursued in many electrochemical energy storage and conversion technologies but remains a great challenge. Here, a novel zirconium‐porphyrin metal–organic framework (MOF) hierarchical nanoframework structure assembled by nanosheets is synthesized. Subsequent pyrolysis and acid etching of such material generates N‐doped hierarchical graphitic carbon nanoframework (N‐GCF) equipped with M‐N4 units. The N‐GCF catalyst demonstrates high ORR activity and stability with large diffusion‐limited current density (6.19 mA cm−2) and half‐wave potential (0.83 V vs reversible hydrogen electrode), which is one of the best carbon‐based ORR catalysts in basic electrolyte. Systematic experiments and characterizations reveal that favorable internal spaces and pores, unique hierarchical structure, and numerous nitrogen‐doped and metal‐N4 species synergistically contribute to the remarkably enhanced catalytic activity for ORR. This work is expected to expand the toolbox for the design and synthesis of MOF‐derived functional materials for electrochemical applications.