Optimization of Fe and Co distribution on Fe-CoZn-ZIF derived polyhedral carbon via secondary adsorption for reversible catalysis of oxygen and zinc-air batteries

Abstract

Bimetallic/polymetallic organic frameworks (MOFs) and their derivants have the advantages of structural adjustable, efficient charge transfer rate and intermetallic synergistic effects which can catalyze oxygen reduction reactions (ORR) and oxygen evolution reaction (OER) efficiently. However, traditional MOFs still faces limited active sites. The construction of catalysts with target active sites using binary/polymetallic MOFs is essential. Here, we prepared catalysts with bimetallic active sites highly dispersed in the interior and surface of N-doped carbon polyhedron via an inside-out (cavity confinement and secondary adsorption) approach. The prepared FeCo@FeCo-CN catalysts exhibited considerable bifunctional catalytic performance, as evidenced by the remarkable improved half-wave potential (E1/2 = 0.878 V) for ORR and the desired overpotential (368 mV) for OER as well as the small potential gap between them (ΔE = 0.720 V). Moreover, the liquid rechargeable Zinc-Air batteries based on the prepared catalyst showed high open-circuit voltage (1.506 V) and specific capacity (890.310 mA h gzn−1) with an impressive cycling stability which is apparently outperformed than Pt/C+RuO2 catalyst. The prime electrocatalytic behavior of the catalyst can be ascribed to the secondary adsorption of Fe and Co which contributes to the generation of more active sites while preventing the undesirable aggregation of metals.