Hierarchical CoFe@N‐Doped Carbon Decorated Wood Carbon as Bifunctional Cathode in Wearable Zn‐Air Battery.

Rechargeable Zn‐air batteries (ZAB) have drawn extensive attention due to their eco‐friendliness and safety. However, the lack of high‐performance and low‐cost oxygen redox reactions (OER and ORR) catalysts has become one of the main stumbling blocks in their development. Herein, we successfully fabricate a CoFe nanobubble encapsulated in nitrogen‐doped carbon nanocage on wood carbon support (CoFe@NC/WC) via pyrolysis of a novel Prussian blue analog (PBA)/spruce precursor. The hierarchical CoFe@NC/WC catalyst exhibits an excellent potential difference of 0.74 V between the OER potential at 10 mA cm−2 and half‐wave potential of ORR in 0.1 M KOH, comparable to recently reported preeminent electrocatalysts. Further, CoFe@NC/WC shows outstanding electrochemical performance in liquid ZAB, with a peak power density of 138.9 mW cm−2 and a specific capacity of 763.5 mAh g−1. More importantly, a bacterial cellulose nanofiber reinforced polyacrylic acid (BC‐PAA) hydrogel electrolyte shows ultrahigh tensile‐breaking stress of 1.58 MPa. In conjunction with the as‐prepared CoFe@NC/WC catalyst, BC‐PAA‐based wearable ZAB displays impressive rechargeability and foldability, and can power portable electronics, such as electronic timer and mobile phone, in bent states. This work provides a new approach toward high‐activity and low‐cost catalysts for ZAB. [ABSTRACT FROM AUTHOR]