Cation-specific modulation of electrochemical oscillation and corrosion film dynamics in the Cu/H3PO4/Cl- system: Ni2+-stabilizing, Al3+-accelerating, and Na+-neutral effects

The electrochemical oscillation (EO) exhibited by Cu anodes during dissolution in H 3 PO 4 /Cl - mixed electrolytes significantly influence the efficacy of processes such as metal surface treatment, precision electroplating, and electrochemical mechanical polishing(ECMP). While Cl - ions have been identified as the key factor inducing oscillations, the mechanism governing their interaction with coexisting cations remains unclear. This study, integrating electrochemical analysis, anodic film surface characterisation, and density functional theory (DFT) calculations, reveals the decisive regulatory role of cations in oscillation mechanisms and corrosion film properties. The findings indicate that, when the influence of Cl - ion concentration is excluded, Na + ions primarily fulfil charge-balancing functions, while Ni 2+ and Al 3+ ions exert synergistic regulatory effects at the active interface. Ni 2+ ions form pure CuCl films through strong adsorption, prolonging oscillation periods. Conversely, Al 3+ ions promote the formation of CuCl/Cu(II)/AlO 4 /Al(OH) x composite films, accelerating film dissolution and shortening periods. The specificity of cations directly determines the stability and dissolution kinetics of films on the Cu anode surface. This study establishes the role of cations as key variables in the electrolytic process, providing a theoretical foundation for understanding EOs and passivation mechanisms.