  The study of ion dissolution from metal surfaces has a long-standing history,
wherein the gradual dissolution of solute atoms with increasing electrode
potential, leading to their existence as ions in the electrolyte with integer
charges, is well-known. However, our present work reveals a more intricate and
nuanced physical perspective based on comprehensive first-principles/continuum
calculations. We investigate the dissolution and deposition processes of 22
metal elements across a range of applied electrode potentials, unveiling
diverse dissolution models. By analyzing the energy profiles and valence states
of solute atoms as a function of the distance between the solute atom and metal
surface, we identify three distinct dissolution models for different metals.
Firstly, solute atoms exhibit an integer valence state following an
integer-valence jump, aligning with classical understandings. Secondly, solute
atoms attain an eventual integer valence, yet their valence state increases in
a non-integer manner during dissolution. Lastly, we observe solute atoms
exhibiting a non-integer valence state, challenging classical understandings.
Furthermore, we propose a theoretical criterion for determining the selection
of ion valence during electrode dissolution under applied potential. These
findings not only contribute to a deeper understanding of the dissolution
process but also offer valuable insights into the complex dynamics governing
metal ion dissolution at the atomic level. Such knowledge has the potential to
advance the design of more efficient electrochemical systems and open new
avenues for controlling dissolution processes in various applications.
