Microscopic Structure of the Metal–Aqueous Electrical Double Layer

Determine the microscopic molecular-scale structure of the electrical double layer at metal–aqueous interfaces, resolving the specific interfacial details that are currently debated across experiments and simulations.

Background

In the discussion of ionic density profiles at Au(111) in aqueous electrolytes, the paper compares predictions from QM/DRISM, Poisson–Boltzmann models, and explicit molecular dynamics. Different studies report conflicting behavior for cation positioning (e.g., Na+ in the inner vs outer Helmholtz plane) and the role of interfacial hydrogen-bond network disruption under bias, while classical theory often expects small cations to remain fully solvated in the outer Helmholtz plane.

The authors show that DRISM results are highly sensitive to Lennard–Jones parameterization and mixing rules, and that pair-specific metal–ion parameters can qualitatively alter interfacial ion profiles and capacitance behavior. Given these discrepant observations and model sensitivities, they explicitly state that the microscopic structure of the electrical double layer at metal–aqueous interfaces is still not fully understood and that several details remain open for debate.