Engineering hierarchical MOFs-derived Fe-N-C nanostructure with improved oxygen reduction activity for zinc-air battery: The role of iron oxide

Abstract The development of non-platinum electrocatalysts for the quick oxygen reduction reaction (ORR) is highly desirable in electrochemical energy conversion technologies such as fuel cells and metal-air batteries. In this work, we synthesize Fe3O4/Fe-N-C-CNT (FeNC) using Fe3+ adsorbed ZIF-8 as a chemical precursor that is obtained in the green and sustainable procedure. FeNC possesses impressive ORR activities, stability and selectivity over that of the commercial Pt/C electrocatalyst in alkaline media, and demonstrates a better peak power density of 118.05 mW cm-2 over that with Pt/C cathode and quicker reaction kinetics when integrated as air electrode catalyst into a primary zinc-air battery. An in-depth investigation confirms that the presence of Fe3O4 increases the wettability of carbon-based composite that promotes the adsorption of the dissolved O2 in the electrolyte solution and extends the triple-phase boundary for ORR, and also protect the active site of Fe-N-C from poisoning. This work sheds light on a sustainable method to synthesize highly efficient non-precious metal-based electrocatalyst from metal-organic-framework precursors and understanding the reaction mechanism for the ORR process for efficient chemical energy to electricity conversion.