Development of Co3O4 nanoparticle-decorated N-doped carbon nanocages as bifunctional electrodes for supercapacitors and Zn–Air batteries

Developing efficient and cost-effective bifunctional electrode materials for both supercapacitor, and zinc-air batteries is important for next generation energy technologies. In this work, cobalt oxide nanoparticle-decorated N-doped porous carbon nanocages (NC@Co 3 O 4 ) were synthesized using template-assisted in-situ polymerization followed by thermal conversion strategy. Structural analysis confirms the formation of N-doped carbon nanocages with a uniform shell thickness (∼26 nm) and a high surface area (702 m 2 g –1 ), providing abundant electrochemical active sites. X-ray photoelectron spectroscopy (XPS) study reveals the coexistence of Co 2+ and Co 3+ species, contributing both pseudocapacitive charge storage and oxygen electrocatalytic activity. A symmetric supercapacitor device assembled with NC@Co 3 O 4 electrodes delivers a high capacitance of 320 F g –1 at 1 A g –1 , achieving a maximum energy density of 44.45 Wh kg –1 at a power density of 500 W kg –1 with 108.59% normalized capacitance after 5000 cycles. Furthermore, the NC@Co 3 O 4 catalyst exhibits promising performance as an air cathode in a liquid zinc-air battery, delivering an open-circuit voltage of 1.46 V, a peak power density of 180.17 mW cm –2 , and a stable charge-discharge process for over 67 h at 2 mA cm –2 with a round-trip efficiency retention of 75.64%. These results demonstrate the potential of NC@Co 3 O 4 nanocages as bifunctional electrodes for energy storage and conversion applications.