Multicomponent Spinel Metal Oxide Nanocomposites as High-Performance Bifunctional Catalysts in Zn-Air Batteries

Although multicomponent transition-metal oxides have been widely studied as electrocatalysts in both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER), precise control of catalytic activities by varying the composition of these metal elements is not an easy task. In this work, we introduce a generic and scalable synthetic method by dealloying a series of Al-rich precursor alloys to produce Mn3O4-based and FeCo-based spinel oxide nanocomposites. It is found that these Mn3O4-based oxides are highly active for the ORR; doping Mn3O4 with Co further enhances the activity while doping with Fe decreases it. For the OER, doping the FeCo-based oxides with Cr, V, or Ni significantly enhances the activity among which Cr is the most effective dopant. Moreover, the addition of Ni into the precursor alloy would inhibit the doping of the negative Fe element into the obtained Mn3O4 after dealloying an AIFeCoNiMn precursor. The obtained (FeCoNi)(3)O-4/Mn3O4 nanocomposite exhibits a high bifunctional electrocatalytic performance, which is comparable with that of the commercial Pt/C + IrO2 combination. When incorporated into a Zn-air battery, the battery can be stably discharged/charged over 400 h with an open-circuit voltage of 1.44 V and a narrow voltage gap of similar to 0.7 V at 2.0 mA cm(-2).