Chemical vapor deposition strategy for inserting atomic FeN4 sites into 3D porous honeycomb carbon aerogels as oxygen reduction reaction catalysts in high-performance Zn-air batteries

Fe-NxC single-atom catalysts have been immensely explored as the most promising ORR catalysts for replacing noble metals. Nevertheless, how to precisely introduce Fe atoms to optimize their spatial distribution and coordination environment in carbonaceous matrices while constructing the hierarchical porous structures to facilitate the mass transport process and ensure the accessibility of Fe-Nx sites remain significant challenges. Here, we propose a strategy to prepare porous N-doped carbon aerogels anchored with single atomic Fe sites (Fe-SA@PNC) as highly efficient ORR electrocatalysts via directional freeze-casting and chemical vapor deposition. Fe-SA@PNC exhibit remarkable ORR activity and stability due to the highly stable honeycomb morphology and hierarchical pore structure, as well as the atomically dispersed Fe-N4 sites in the carbon support. Furthermore, the practical application of Fe-SA@PNC catalysts as cathode materials in Zn-air batteries was demonstrated with encouraging performance. This study provides a promising approach for constructing high-efficiency ORR single-atom catalysts.