Hollow Co/N-C@NiCo2O4 Spheres as Highly Efficient Bifunctional Oxygen Electrocatalysts for Rechargeable Zinc-Air Batteries

In this paper, hollow Co/N-C@NiCo2O4 spheresassembled by nanoparticles were developed as efficient bifunctionalcatalysts for zinc-air batteries. The hollow structure is synthesizedwith ZIF-67 as a reactant template. NiCo-LDH grown on the ZIF-67 surfacemaintains its structural integrity during heat treatment and reducesthe agglomeration of the material, which promotes charge transportduring the catalytic process. The hollow structure has a specificsurface area of 124.3 m(2) g(-1) with richcatalytic active sites. As expected, the power density of the Co/N-C@NiCo2O4-based Zn-air battery is 176 mW cm(-2) and the specific capacity is 745 mAh g(-1), with 1.45 V open-circuit voltage and 100 h cycling life, much betterthan those of the 20% Pt/C-RuO2-based Zn-air battery(1.42 V, 133 mW cm(-2), 721 mAh g(-1)).