Facile crafting of ultralong N-doped carbon nanotube encapsulated with FeCo nanoparticles as bifunctional electrocatalyst for rechargeable zinc-air batteries

The rational design and facile preparation of highly efficient bifunctional electrocatalysts toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) still remain challenge. Herein, we report the facile preparation of a bifunctional electrocatalyst consisting of FeCo alloy nanoparticles embedded in ultralong N-doped carbon nanotube (denoted FeCo/LNCNT) by capitalizing on the coordination interaction between triphenylimidazole-containing crosslinked polymer and metal salts followed by the two-step pyrolysis under the presence of melamine. The FeCo alloy nanoparticles play the crucial role in the formation of ultralong carbon nanotube with increasing pyrolysis time under the assistance of melamine. The resulting FeCo/LNCNT manifests remarkable ORR and OER activity together with outstanding durability. The small potential gap (0.756 V) of FeCo/LNCNT demonstrates a promising application as ORR/OER bifunctional elctrocatalyst. The assembled zinc-air battery using FeCo/LNCNT as the air anode exhibits higher open-circuit voltage (1.52 V), specific capacity (779 mAh g−1Zn) and power density (144 mW cm−2) than the Pt/Ir counterpart. Notably, the zinc-air battery assembled with FeCo/LNCNT can remain stable for more than 600 cycles without significant voltage drop and efficiency loss, representing an excellent cycling stability.