Angew. Chem. Int. Ed., 2018, 57, 16166–16170

Xu Liu, Lei Wang*, Peng Yu, Chungui Tian, Fanfei Sun, Jingyuan Ma, Wei Li, Honggang Fu*. A stable bifunctional catalyst for rechargeable zinc–air batteries: iron–cobalt nanoparticles embedded in a nitrogen-doped 3D carbon matrix. (Angew. Chem. Int. Ed., 2018, 57, 16166–16170)

Low-cost, efficient bifunctional electrocatalysts are needed to mediate the oxygen reduction and oxygen evolution reactions (ORR/OER) in Zn–air batteries. Such catalysts should offer binary active sites and an ability to transfer oxygen-based species and electrons. A 3D catalyst, composed of nanoparticles of CoFe alloy embedded in N-doped carbon nanotubes tangled with reduced graphene oxide, was developed, which presents appreciable ORR/OER activity when applied in a Zn–air battery. A high open-circuit voltage of 1.43 V, a stable discharge voltage of 1.22 V, a high energy efficiency of 60.1%, and excellent stability after 1600 cycles at 10 mAcm @2 are demonstrated. An all-solid-state battery had an outstanding lifetime and high cell efficiency even upon bending. In situ X-ray absorption spectroscopy revealed that OOH* and O* intermediates induce variations in the Fe @ Fe and Co @ Co bond lengths, respectively, suggesting that Fe and Co species are crucial to the ORR/OER processes.