Single-atom palladium anchored N-doped carbon towards oxygen electrocatalysis for rechargeable Zn-air batteries.

Herein, an atomically dispersed palladium catalyst on a hierarchical porous structure of N-doped carbon (Pd 1 /N-C) is prepared using a facile freeze-drying-assisted strategy. Freeze-drying methods not only suppress the aggregation of Pd atoms but also successfully produce abundant nanopores. HAADF-STEM confirms that Pd single atoms are uniformly anchored on the N-C surface. The Pd 1 /N-C electrocatalyst enhances the ORR and OER activity and durability compared to N-C and Pd-NPs/N-C. Rechargeable Zn-air batteries (ZABs) based on novel Pd 1 /N-C exhibit a peak power density of 113.7 mW cm -2 and maintain a voltage efficiency of 64.0% after 495 cycles at a discharge current density of 5 mA cm -2 . Besides, two ZABs in series can supply an LED light for at least 170 h.