N-Decorated Main-Group MgAl 2 O 4 Spinel: Unlocking Exceptional Oxygen Reduction Activity for Zn-Air Batteries.

The development of economical and efficient oxygen reduction reaction (ORR) catalysts is crucial to accelerate the widespread application rhythm of aqueous rechargeable zinc-air batteries (ZABs). Here, a strategy is reported that the modification of the binding energy for reaction intermediates by the axial N-group converts the inactive spinel MgAl 2 O 4 into the active motif of MgAl 2 O 4 -N. It is found that the introduction of N species can effectively optimize the electronic configuration of MgAl 2 O 4 , thereby significantly reducing the adsorption strength of *OH and boosting the reaction process. This main-group MgAl 2 O 4 -N catalyst exhibits a high ORR activity in a broad pH range from acidic and alkaline environments. The aqueous ZABs assembled with MgAl 2 O 4 -N shows a peak power density of 158.5 mW cm -2 , the long-term cyclability over 2000 h and the high stability in the temperature range from -10 to 50 °C, outperforming the commercial Pt/C in terms of activity and stability. This work not only serves as a significant candidate for the robust ORR electrocatalysts of aqueous ZABs, but also paves a new route for the effective reutilization of waste Mg alloys.