Electrochemical conversion of CO₂ in electrolyzers is a promising pathway toward sustainable fuel and chemical production. A central component of many electrolyzer designs is the gas diffusion electrode (GDE), which enables efficient delivery of gaseous CO₂ to the catalyst surface. However, understanding the local reaction environment within gas diffusion electrodes (GDEs) remains a major challenge, as nanoscale species organization is difficult to access experimentally. Yet, these confined interfacial regions play a crucial role in governing the performance of electrochemical CO₂ reduction (CO₂RR) systems. In particular, how CO₂ and ions behave near complex solid–liquid–gas interfaces under applied potential remains an open question—especially within confined pores just a few nanometers wide (≈6 nm), where continuum models no longer hold. This thesis addresses that challenge using all-atom molecular dynamics (MD) simulations to explicitly resolve the formation and behavior of the electric double layer in a KHCO₃–CO₂ system confined within a slit nanopore bounded by substrate walls with alternating hydrophilic and hydrophobic regions. The Constant Potential Method (CPM), based on the Siepmann–Sprik polarizable electrode model, is used to apply different electrode potentials by allowing the electrode to dynamically respond to the surrounding electrolyte environment through fluctuating atomic charges. Spatially resolved one- and two-dimensional profiles reveal that charged surfaces induce strong ionic layering, while CO₂ is repelled from dense interfacial zones and instead accumulates along triple-phase boundaries (TPBs). This localization becomes more pronounced with increasing cathodic bias, indicating a field-assisted enrichment mechanism. Such behavior reflects experimental observations from gas-fed CO₂ electrolyzers, where conversion rates are highest near TPBs. Additionally, lateral heterogeneities driven by surface chemistry and confinement emerge clearly in the MD results—features that are absent in continuum approaches. These findings provide a foundation for future simulation and experimental studies aiming to engineer local CO₂ environments, and contribute to broader efforts in optimizing interface-driven transport in electrochemical and catalytic systems.