Ligand-Assisted Surface Doping of Colloidal Ag ₂ S Nanocrystals for Efficient H ₂ O ₂ Electrosynthesis via the Two-Electron Oxygen Reduction Reaction

Doping provides an effective strategy for tailoring the surface and electronic structures of electrocatalysts; however, conventional approaches often suffer from limited dopant incorporation, heterogeneous distribution, and degradation of crystallinity. Here, we report a ligand-assisted surface doping that enables uniform Co incorporation into colloidal Ag₂S nanocrystals (NCs) for highly efficient and selective two-electron oxygen reduction reaction (2e^─ ORR) toward hydrogen peroxide (H₂O₂) production. Surface ligands regulate the interaction between Co ions and the NC surface, facilitating controlled dopant diffusion and stabilizing incorporation sites, which in turn enables precise modulation of the electronic structure and adsorption of oxygen intermediates. Significantly, this optimal electronic tuning facilitates a more efficient interfacial charge-transfer process. This ligand-assisted framework suppresses the formation of dopant-derived clusters, preserves the structural integrity of the NCs, and maximizes catalytic surface activity. As a result, the Co-doped Ag₂S NCs deliver over 90% Faradaic efficiency for H₂O₂ generation across a wide potential window and achieve a remarkable H₂O₂ yield rate of 590 mmol g^-1 h^-1 at 0 V versus RHE, outperforming their pristine counterpart. These findings establish ligand-assisted surface doping as an effective approach for designing advanced NC-based electrocatalysts.