Engineering Asymmetric Electronic Structure of Co─N─C Single-Atomic Sites Toward Excellent Electrochemical H₂O₂...

To advance electrochemical H₂O₂ production and unravel catalytic mechanisms, the precise structural coordination of single-atomic M-N-C electrocatalysts is urgently required. Herein, the Co─N₅ site with an asymmetric electronic configuration is constructed to boost the two-electron oxygen reduction reaction (2e^- ORR) compared to symmetric Co─N₄, effectively overcoming the trade-off between activity and selectivity in H₂O₂ production. Both experimental and theoretical analyses demonstrate that breaking the symmetry of Co─N sites promotes the activation of O₂ molecules and moderates the adsorption of the key *OOH intermediate by disrupting the linear scaling relationship for intermediates adsorption. This modulation enables efficient H₂O₂ production and its effective retention for subsequent applications. As a proof of concept, Co─N₅ achieves a H₂O₂ production rate as high as 16.1 mol g_cat ^-1 h^-1 in a flow cell, outperforming most recently reported counterparts. Furthermore, the coupling of 2e^- ORR with the oxidation of cellulose-derived carbohydrates accomplishes high formic acid yields (84.1% from glucose and 62.0%-92.1% from other substrates), underpinning the sustainable electro-refinery for biomass valorization at ambient conditions. By elucidating the intrinsic relationship between 2e⁻ ORR and the asymmetry of single-atomic sites, this work paves the way for high-performance electrosynthesis.