Abstract
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 -2V < U (SHE) < 2V, 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).