Uncovering Dynamic Edge-Sites in Atomic Co-N-C Electrocatalyst for Selective Hydrogen Peroxide Production

Understanding the nature of single-atom catalytic sites and identifying their spectroscopic fingerprints are essential prerequisites for the rational design of target catalysts. Here, we apply correlated in situ X-ray absorption and infrared spectroscopy to probe the edge-site-specific chemistry of Co-N-C electrocatalyst during the oxygen reduction reaction (ORR) operation. The unique edge-hosted architecture affords single-atom Co site remarkable structural flexibility with adapted dynamic oxo adsorption and valence state shuttling between Co^(2-δ)+ and Co²⁺ , in contrast to the rigid in-plane embedded Co₁ -N_x counterpart. Theoretical calculations demonstrate that the synergistic interplay of in situ reconstructed Co₁ -N₂ -oxo with peripheral oxygen groups gives a rise to the near-optimal adsorption of *OOH intermediate and substantially increases the activation barrier for its dissociation, accounting for a robust acidic ORR activity and 2e^- selectivity for H₂ O₂ production.