Underpotential deposition of copper on Au(111) is analyzed in the light of first-principles calculations. The existence of a 1 × 1 Cu monolayer on Au(111) at underpotentials can be only understood taking into account the free energy excess delivered by the adsorption of sulfate anions. While a naked copper pseudomorphic monolayer results thermodynamically less stable than bulk copper, accounting for the interaction with sulfate ions delivers an underpotential shift which is comparable with the experimental value.
Velez, P., Cuesta, A., Leiva, E. P. M., & Macagno, V. A. (2012). The underpotential deposition that should not be: Cu(1x1) on Au(111). Electrochemistry Communications, 25, 54-57. https://doi.org/10.1016/j.elecom.2012.09.024