Chemical ordering and kinetic roughening at metal-electrolyte interfaces

In spite of the intense effort devoted in the last few years to understanding the complex dynamics of the different (electro-)chemical and physical mechanisms that take part in the metallic dissolution process, the influence of the dissolution reactive mechanism on the surface dynamics is still an open question. We present the results obtained from simulations of a microscopic metal-electrolyte interface model. The model considers a single-crystal metal that dissolves according to a reactive scheme with intermediate adsorbed species. Simulations show that roughness development induces a direct relationship between the spatial and temporal scales of the model. As a consequence of that, the time ordering of the chemical species intrinsic to the dissolution mechanism is projected spatially, leading to an unexpected chemical ordering on the interface. We show how this self-organization depends on the overall reaction kinetics and that it can be modeled from the standard macroscopic approach. One of the main consequences of the chemical ordering is that dissolution is no longer random. The heterogeneous distribution of dissolution active sites gives rise to active dissolution domains on the surface, resulting in different degrees of roughness with respect to the random dissolution reference model. These morphological differences persist in all scales. An important consequence of such complex behavior is that surface morphology changes when the electrode potential is varied during driven electrochemical dissolution. This is a remarkable result if we take into account the fact that the proposed interface model evolves under very simple conditions, namely, surface reaction kinetic control and reactivity not dependent on the local or global surface structure. Therefore, the results presented in this paper contribute to the description of metal-electrolyte interface structure and to the understanding of the processes that participate in the surface roughening observed during driven metal dissolution.