ABSTRACT
Motivated by the importance of Cl- in the industrial electrolytic Cu plating process, we study the coadsorption of Cl- and Cu2+ 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 Cu2+ coadsorption, we identified five stable phases for electrode biases between -2V < U SHE < 2V, with two being Cl- adsorption phases, two being Cl- + Cu2+ coadsorption phases and one being a pure Cu2+ 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 Cu2+ adsorbates on the Cu (110) substrate. In addition, by studying the free energy of adsorption of Cu2+ onto pristine and Cl- covered Cu (110), we conclude that the introduction of Cl- ion does not improve the energetics of Cu2+ adsorption onto Cu (110).
