Hierarchical construction of Co nanoparticles embedded in an N doped carbon nanotube/porous nanosheet electrocatalyst for Zn–air batteries†

Inefficient cathodic reactions severely limit the practical performance of rechargeable zinc–air batteries (RZABs) and become a fundamental bottleneck in their development. The exploitation of cost-effective cathode electrocatalysts is significant for addressing this issue. Herein, we demonstrate a facile programmed annealing strategy to fabricate an efficient electrocatalyst with a structure of Co nanoparticles embedded in N doped carbon nanotubes/porous nanosheets (Co@DUGC). Benefiting from the in situ wrapped Co nanoparticles and doped N as catalytic and adsorptive sites, and a hierarchical carbon nanotube/porous nanosheet architecture for fast electron transfer and mass diffusion, the fabricated Co@DUGC exhibits excellent bifunctional electrocatalytic performance with a positive half-wave potential of 0.87 V in the ORR and a low overpotential of 414 mV in the OER. As a cathodic catalyst, Co@DUGC endows a home-made liquid RZAB with a high peak power density of 150 mW cm⁻², a large specific discharge capacity of 816.9 mA h g_Zn⁻¹ and a durable rechargeability of 314 cycles. Meanwhile, a button RZAB based on Co@DUGC displays a peak power density of 85.3 mW cm⁻², a specific discharge capacity of 643.7 mA h g_Zn⁻¹ and a charge–discharge cycle life over 95 times, revealing its reliability for portable applications. This work demonstrates a convenient and rational design of transition metal decorated carbon electrocatalysts for high-performance RZABs.