Electrochemical measurements and atomistic simulations of Cl⁻-induced passivity breakdown on a Cu₂O film

The mechanism of passivity breakdown on Cu₂O films was studied. The thickness and components of the film were estimated by EIS, AES and XPS analyses. The structural relaxations, energies, electronic properties and diffusion coefficients were calculated by first-principles calculations. Both the experimental and calculated results demonstrate that the film thinning is due to the adsorption of Cl⁻ on the surface instead of a penetration process. The inner point defects facilitate the adsorption of Cl⁻, and the introduction of Cl⁻, in turn, increases the transport rate of point defects. A theoretical model was proposed, which is also applicable to local breakdown.