Assessing a First-Principles Model of an Electrochemical Interface by Comparison with Experiment

Electrified interfaces
are central for electrocatalysis, batteries,
and molecular electronics. Experimental characterization of these
complex interfaces with atomic resolution is highly challenging. First-principles
modeling could provide a link between the measurable quantities and
an atomic scale understanding. However, such simulations are far from
straightforward. Although approaches that include the effect of the
potential and the electrolyte have been proposed, detailed validation
has been scarce and ”indirect” since atomically resolved
experimental studies of systems that can be convincingly simulated
are scarce. We introduce here the adsorption of pyridine on Au(111)
as a convenient and relevant model: the adsorption mode of pyridine
switches as a function of the electrochemical potential. We demonstrate
that the primitive surface charging model gives qualitatively correct
results at a low complexity. For quantitative agreement, however,
the model needs to include a more realistic description of the electrical
double layer. Approximating the latter through the linearized Poisson–Boltzmann
equation leads to a quantitative improvement, lowering the error in
the transition potential from 1 V to an acceptable 0.3 V. Hence, we
demonstrate the qualitative usefulness of the surface charging method
and the excellent agreement that can be obtained by slightly more
sophisticated electrolyte models.