Atomization driven crystalline nanocarbon based single-atom catalysts for superior oxygen electroreduction

Atom-migration-trapping (AMT) is an effective and straightforward strategy for fabricating single-atom catalysts (SACs), but understanding the mechanism and effects of anchoring sites on AMT are formidable challenges. Here, we demonstrate that AMT phenomena occurs in crystalline porous nanocarbon, which allows development of highly efficient SACs via systematic investigation of atomization process and chemical state of active sites. An arc discharge-based bottom-up synthesis can generate an ideal porous nanocarbon with controllable nitrogen functionality, containing metal nanoparticles for AMT. Pre-formed N-functionalities in as-synthesized catalyst play important role in capturing single metal species, while additional ammonia treatment successfully modulates coordination geometry of active sites. The atomic cobalt catalyst exhibits superior oxygen reduction activity with remarkable power performance in single-cell experiments (752 mW cm⁻²), exceeding the reported Co-N atomic catalysts. Our findings provide not only new perspectives in AMT phenomena but also strategies to develop an efficient and practical SACs in energy conversion systems.