Organic lactam induces the secondary recrystallization of zeolite β to form hierarchical porous carbon nanocages for efficient oxygen reduction and Zn-air batteries

In this study, we present a novel synthesis of hierarchical carbon nanocages (HCNC) with diverse pore structures tailored for efficient oxygen reduction reactions (ORR) and advanced performance in zinc-air batteries (ZABs). The hierarchical structure was achieved using a dissolution-recrystallization strategy, where N, N-dimethylpyrrolidone was employed to activate the zeolite β framework. The resultant hierarchical β-zeolite nanocage (HβNC) was subsequently used as a template for synthesizing the HCNC via chemical vapor deposition. The HCNC exhibited a multilevel porous structure, including micropores, mesopores, and macropores, optimizing mass transfer and providing high surface area for active site exposure. By introducing Fe-Nx active sites through an impregnation-pyrolysis method, the Fe–N/HCNC catalyst was synthesized and tested for ORR. The catalyst demonstrated superior activity, stability, and corrosion resistance, outperforming commercial Pt/C catalysts with a half-wave potential of 0.905 V. Additionally, the Fe–N/HCNC-based ZAB displayed excellent electrochemical performance, high power density, and enhanced durability. The This work not only provides a novel approach to carbon nanocage synthesis, and the unique structural characteristics of HCNC offer promising opportunities in energy storage and conversion technologies, addressing limitations in catalyst stability and mass transport.