Co-Incorporated N-Doped Micro–Meso Porous Carbon as an Electrocatalyst for Oxygen Reduction Reaction and Zn–Air Battery

Abstract

Metal–organic frameworks are considered ideal precursors for the preparation of transition-metal, heteroatom-doped carbon catalysts that are perceived to be efficient electrocatalysts for energy storage devices. Herein, we demonstrate the synthesis of ZIF-67-derived Co-incorporated N-doped porous carbon catalysts supported on high surface area microporous carbon prepared from a lotus seed shell. The combination of the two carbon catalysts in different weight ratios resulted in Co-incorporated N-doped carbon sheets with tuned surface area and porosity, enabling enhanced oxygen reduction reaction (ORR) activity in an alkaline medium. The optimized carbon catalyst ZL 600 (3:1) exhibited a half-wave potential of 0.79 V vs RHE and a limiting current density of −4.38 mA cm–2 in 0.1 M KOH solution with higher stability and methanol tolerance. The optimized sample ZL 600 (3:1) demonstrated as a cathode in a zinc–air battery exhibited an open circuit voltage of 1.29 V with a flat discharge profile at a current rate of 10 mA cm–2. The homemade system produced a specific capacity of 610 mAh g–1 and a peak power density of 111 mW cm–2, comparable to the cathode made with Pt/C. The high micro-mesoporosity, pyridinic and pyrrolic nitrogen contents, as well as enriched Co-active centers protected by carbon sheets favorably contributed to the efficient ORR mechanism.