Electrocatalytic oxygen reduction of COF-derived porous Fe-Nx nanoclusters/carbon catalyst and application for high performance Zn-air battery

Abstract

The development of non-previous-metal electrocatalyst with low cost, high activity and stability towards oxygen reduction reaction (ORR) remains a challenge. Covalent organic frameworks (COFs) have emerged as promising candidates for the preparation of porous metal/nitrogen co-doped carbon catalysts. In the present work, porous Fe-Nx nanoclusters/carbon catalysts are prepared by pyrolyzing iron-containing covalent-triazine organic frameworks. It is found that the synthesis conditions including pyrolysis temperature and pressure have great impacts on the surface area of micropores, mesopores and macropores, which in turn influences the ORR activity of catalysts by varying the mass diffusion and the contact of active centers with electrolytes. The optimized catalyst (denoted as Fe1.2NC-0.02-800), having the highest both BET and external surface areas, shows much higher kinetic current density and catalytic stability than commercial Pt/C catalyst in ORR process. When being assembled into Zn-air battery, it also exhibits excellent performances in terms of open circuit voltage (1.45 V), power density (210 mW cm−2 at 330 mA cm−2) and specific capacity (713.1 mA h gZn−1), which outperform the corresponding values of Pt/C-based Zn-air battery. Moreover, 15 light-emitting diodes can be powered by two series-connected Zn-air batteries with Fe1.2NC-0.02-800 as the air-cathode catalyst, implying its promising application in clean energy conversion field.