Self-etched bimetallic hybrid derived cobalt/zinc dual-sites coordinated N, P-codoped hollow carbon polyhedron for efficient oxygen reduction reaction

Hollow structure with hierarchical pore is benefit for the exposure of active sites, showing great advantages in electrocatalysis. Whereas, it still a challenge for the target preparation of such architecture in a simple, but efficient ways. Herein, a Co/Zn-Nx (Nx represents the number of N atoms (x) coordinated with Co or Zn atoms) dual sites anchored N, P-codoped hollow carbon polyhedron (PZH-800) with well-defined Co species was facilely prepared via direct pyrolysis of a bimetallic hybrid (PZH) obtained by polymerization-coating of Zn-porphyrin polymer on the surface of zeolitic-imidazolate-framework (ZIF-67). The hollow architecture was formed via self-etching, in which the hydrochloric acid produced during the formation of hybrid etched the inner acid-degradable ZIF-67. Different with post-etching method, self-etching could really preserve the original structure and catalytic sites, better regulate the electronic structures, enhancing the catalytic activity. Compared with the Co or Zn mono-doped sample, PZH-800 presented an enhanced ORR activity with a half-wave potential (E1/2) of 0.94 V (vs. RHE), as well as outstanding stability, outperforming commercial Pt/C (20%) in alkaline media. Impressively, ZABs using PZH-800 as the cathodic catalyst demonstrated a maximum power density (280 mW cm−2), coupled with a remarkable running stability, surpassing the battery catalyzed by Pt/C. This work paves a new avenue for the future development of MOF-derived non-precious metal-based hollow catalysts