Electrocatalytic kinetics is strongly influenced by properties of electric double layer. Approaches towards representing the electric double layer at a molecular scale is challenged by the requirement of sampling extensive time and length scales. Therefore, approximations in the description of double layer are needed to allow practical utility towards designing better electrocatalytic systems. Most of these approximations relate to the description of the two salient features of the double layer, the solvent and the ions causing interfacial electric field. As the model gets more complex, it gets increasingly difficult to demarcate the sensitivity of the model choices representing these features on the predicted reaction energetics. For example, models such as continuum electrolyte distribution allow realistic distribution of ions through parameters such as Debye length but the influence of Debye length can’t be separated from the influence of other purely computational parameter such as cutoff-density.<br/><br/>We propose a compartmentalized approach to model the influence of electric field and solvation by considering a Helmholtz model of double layer with solvation described through a combination of specific solvation and continuum solvation. Helmholtz model is a crude but interpretable approximation to the electric double layer and require only two parameters (ε and d) to describe the double layer electric field. These parameters not only directly correlate to the microscopic structure of double layer but also to the overall measurable macroscopic capacitance of the system. Using this model, we show that the dipole change along the reaction path is the most important determinant towards sensitivity of the kinetics to double layer. In this talk , we will share results on the sensitivity of barrier estimates to model choices with a series of electrochemical interface models and apply these to examine elementary reactions relevant to the oxygen reduction reaction, ammonia electrosynthesis, and carbon dioxide electro-reduction.

Choices for modeling the influence of interfacial double layer on electrocatalytic kinetics using density functional theory

ACS Spring 2022

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