Revealing isolated M‐N3C1 active sites for efficient collaborative oxygen reduction catalysis

Single atom catalysts (SACs) are of great importance for oxygen reduction, a critical process in renewable energy technologies such as fuel cells and metal-air batteries. The catalytic performance of SACs largely depends on the structure of their active sites, but explorations of highly active structures for SAC active sites are still limited. Herein, we demonstrate a combined experimental and theoretical study of oxygen reduction catalysis on SACs, which incorporate M-N 3 C 1 site structure, composed of atomically dispersed transition metals (e.g., Fe, Co, and Cu) in nitrogen doped carbon nanosheets. The resulting SACs with M-N 3 C 1 sites exhibited prominent oxygen reduction catalytic activities in both acidic and alkaline media, following the trend Fe-N 3 C 1 > Co-N 3 C 1 > Cu-N 3 C 1 . Theoretical calculations suggest the C atoms in these structures behave as collaborative adsorption sites to M atoms, thanks to interactions between the d / p orbitals of the M/C atoms in the M-N 3 C 1 sites, enabling dual site oxygen reduction. Compared with the common single site mechanism, the proposed dual site mechanism was determined to be more favorable for oxygen reduction catalysis, in good agreement with the experimental findings.