Contrasting Views of the Electric Double Layer in Electrochemical CO 2 Reduction: Continuum Models vs Molecular Dynamics

作者：Evan F. Johnson, Sophia Haussener · 发表于：The Journal of Physical Chemistry C · 年份：2024 · DOI：10.1021/acs.jpcc.4c03469 · 被引用次数：25 · 研究领域：CO2 Reduction Techniques and Catalysts、Ionic liquids properties and applications、Covalent Organic Framework Applications

High Resolution Image Download MS PowerPoint Slide In the field of electrochemical CO 2 reduction, both continuum models and molecular dynamics (MD) models have been used to understand the electric double layer (EDL). MD often focuses on the region within a few nm of the electrode, while continuum models can span up to the device level (cm). Still, both methods model the EDL, and for a cohesive picture of the CO 2 electrolysis system, the two methods should agree in the regions where they overlap length scales. To this end, we make a direct comparison between state-of-the-art continuum models and classical MD simulations under the conditions of CO 2 reduction on a Ag electrode. For continuum modeling, this includes the Poisson–Nernst–Planck formulation with steric (finite ion size) effects, and in MD the electrode is modeled with the constant potential method. The comparison yields numerous differences between the two modeling methods. MD shows cations forming two adsorbed layers, including a fully hydrated outer layer and a partial hydration layer closer to the electrode surface. The strength of the inner adsorbed layer increases with cation size (Li + < Na + < K + < Cs + ) and with more negative applied potentials. Continuum models that include steric effects predict CO 2 to be mostly excluded within 1 nm of the cathode due to tightly packed cations, yet we find little evidence to support these predictions from the MD results. In fact, MD shows that the concentration of CO ...