Synthesis of hierarchical porous cobalt and nitrogen-doped carbon catalysts for enhancing the durability of zinc-air batteries

The development of efficient and durable non-precious metal-based bifunctional oxygen electrocatalysts is pivotal in realizing cost-effective and high-performance rechargeable Zinc-Air Batteries (ZABs). Herein, a unique SiO₂-template-assisted in-situ pyrolysis and etching strategy was employed to synthesize the Co-100-900@SiO₂ catalyst, a cobalt-nitrogen co-doped carbon material with a hierarchical porous structure. This spherical hierarchical porous structure is unique and robust, its mesoporous and macroporous structures significantly improve the microenvironment at the “solid-gas-liquid” three-phase interface at the gas diffusion electrode, effectively balancing the efficient transport of reactants and products, access to active sites, and structural stability. Consequently, the catalyst exhibits excellent bifunctional catalytic activity for both ORR and OER. In 0.1 mol/L KOH, the ORR half-wave potential is 0.799 V, and the limiting diffusion current density is 4.3 mA·cm⁻². At a current density of 10 mA·cm⁻², the OER overpotential is 0.66 V. A rechargeable zinc-air battery constructed using this material achieved a power density as high as 155.4 mW·cm⁻². After 1500 charge-discharge cycles at a current density of 5 mA·cm⁻², the voltage gap remained around 0.89 V, demonstrating exceptional durability. This study successfully achieved improved stability while maintaining high activity, providing new insights for the design of next-generation high-performance, long-life rechargeable zinc-air batteries.