First-principles study of coadsorption of Cu 2+ and Cl - ions on the Cu (110) surface.

Motivated by the importance of Cl - in the industrial electrolytic Cu plating process, we study the coadsorption of Cl - and Cu 2+ on the Cu (110) surface using first-principles density functional theory (DFT) calculations. We treat the solvent implicitly by solving the linearized Poisson-Boltzmann equation and evaluate the electrochemical potential and energetics of ions with the computational hydrogen electrode approach. We find that Cl - alone is hardly adsorbed at sufficiently negative electrochemical potentials μ Cl but stable phases with half and full Cl - coverage was observed as μ Cl is made more positive. For Cl - and Cu 2+ coadsorption, we identified five stable phases for electrode biases between -2 V < U SHE < 2 V , with two being Cl - adsorption phases, two being Cl - + Cu 2+ coadsorption phases and one being a pure Cu 2+ adsorption phase. In general, the free energy of adsorption for the most stable phases at larger | U SHE | are dominated by the energy required to move electrons between the system and the Fermi level of the electrode, while that at smaller | U SHE | are largely dictated by the binding strength between Cl - and Cu 2+ adsorbates on the Cu (110) substrate. In addition, by studying the free energy of adsorption of Cu 2+ onto pristine and Cl - covered Cu (110), we conclude that the introduction of Cl - ion does not improve the energetics of Cu 2+ adsorption onto Cu (110).