Defect-Suppressed Molecular Passivation Film Endure the Trade-Off: Scalable Co-Passivation for Copper That Withstands Harsh Alkaline Attack.

The persistent corrosion of copper in aggressive environments remains a fundamental limitation, challenges related to interfacial integrity, durability, and practical processability have not to be fully addressed. Here, we propose a synergistic passivation strategy with 1-dodecanethiol (DT) and 2-mercaptobenzimidazole (MBI) into a low-defect, ultrathin passivation film on copper. The molecularly engineered passivation film affords a four-order-of-magnitude improvement in corrosion current suppression. Notably, the Cu-DT-MBI preserves this four-order-of-magnitude protection even after 24-h immersion in 1 M NaOH and maintains effective corrosion resistance for more than 13 days. A combination of in situ spectroscopy and cross-sectional electron microscopy reveals a uniform and continuous passivation film with a thickness of 1.03 nm. The enhanced protection is attributed to the functional complementarity between DT and MBI: DT contributes a hydrophobic alkyl-chain barrier, while MBI preferentially coordinates with under-coordinated Cu sites and improves interfacial continuity. DFT calculations further indicate that the passivated surface weakens O2 and Cl- adsorption, thereby suppressing oxidation and corrosion. Furthermore, a roll-to-roll manufacturing process was demonstrated to produce passivated Cu foils that retain excellent conductivity while withstanding harsh alkaline attack. This work provides a foundational framework for designing ultra-stable molecular interfaces via synergistic passivation.