Revealing the Active Sites in Atomically Dispersed Multi-Metal-Nitrogen-Carbon Catalysts

Atomically dispersed metal-nitrogen-carbon catalysts have been extensively explored for various sustainable energy-related reactions. From a material perspective, these catalysts are likely to consist of a combination of single-atom, dual-atom and possibly even multi-atom sites. However, pinpointing their true active sites has remained a challenging task. In this study, a model catalyst is introduced, Co/CoMn-NC, featuring both Co single-atom sites and CoMn dual-atom sites on a nitrogen-doped carbon substrate. By employing a combination of X-ray adsorption spectroscopy and density functional theory calculations, the atomic configuration of Co/CoMn-NC has been determined. Density functional theory calculations are also used to unequivocally identify Co-atom within the CoMn dual-atom motif as the predominate active site of the Co/CoMn-NC model catalyst toward oxygen reduction reaction (ORR), which is further confirmed by in situ Raman spectroscopy. The cooperative interactions between Co single-atom sites and CoMn dual-atom sites can finely tune the d-band center and ameliorate the adsorption and desorption behaviors of the intermediates, thereby facilitating ORR kinetic. Overall, the study introduces a systematic strategy to elucidate the structure and the superiority of the model system and provides new insights into atomically dispersed multi-metal active sites, showcasing that enhanced catalytic performance extends beyond unified diatomic sites or monatomic sites. A new model diatomic catalyst, Co/CoMn-NC, comprising Co single-atom sites and CoMn composite sites, is constructed on an N-doped carbon substrate. The structure of this catalyst containing various types of active sites is elucidated via a systematic strategy. Thanks to the synergy between Co single-atom sites and CoMn dual-atom composite sites, Co/CoMn-NC demonstrates excellent ORR performance and remarkable long-term durability. image