Electronic Modulation of Cobalt Single-Atom Catalysts via In-Plane and Axial Coordination Engineering for Enhanced H₂O₂ Electrosynthesis

Abstract

Cobalt-based single-atom catalysts (Co SACs) have emerged as attractive candidates for promoting the two-electron oxygen reduction reaction (2e⁻ ORR) toward efficient H₂O₂ generation. Yet universal strategies to regulate their electronic structure remain limited. Here, we demonstrate that in-plane and out-of-plane heteroatom coordination modulates the Co electronic states, thereby governing 2e⁻ ORR activity and selectivity. By correlating atom-induced charge redistribution with H₂O₂ production efficiency, we establish a general design strategy for SACs with tunable performance. Incorporating electron-withdrawing O or electron-donating N creates asymmetric Co-N_xO_y-O-C sites, among which Co-N₅-O-C is most effective. Its electron-rich Co center in a distorted pentacoordinate geometry promotes 2e⁻ ORR, achieving 90% H₂O₂ selectivity and 89.5 A g⁻¹ in mass activity under 0.65 V versus RHE conditions, outperforming symmetric Co-N₄-O-C and electron-deficient Co-N₂O₂-O-C. Density functional theory reveals that electron-donating N in Co-N₅ broadens the Co dz² orbital near the Fermi level, weakening *OOH binding, whereas in-plane O in Co-N₂O₂ withdraws electrons, increasing empty d-states and strengthening *OOH adsorption. Under flow-cell conditions, Co-N₅-O-C delivered 15.88 mol g_cat⁻¹ h⁻¹ H₂O₂ (300 mA cm⁻²) with >88% Faradaic efficiency over 50 h and enabled complete degradation of 50 ppm pollutants within 10 min, demonstrating practical potential for wastewater treatment.

Keywords

cobalt single-atom catalysts / coordination environment engineering / hydrogen peroxide synthesis

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