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Electric Double Layer: From Classical Stern-like Models to Advanced Continuum Theories
The electric double layer (EDL) governs charge distribution at electrode–electrolyte interfaces, controlling reaction kinetics and energy storage performance. This mini review surveys the evolution of EDL theory—from the classical Gouy-Chapman-Stern framework to modern coupled quantum-continuum schemes that integrate electronic structure with statistical mechanics. We show how modified Poisson–Boltzmann (mPB) formu-lations incorporating finite ion size, dielectric saturation, and ion polarizability extend continuum predic-tive power. Classical density functional theory (cDFT) emerges as the most rigorous continuum route, capturing structural layering, ion correlations, and specific adsorption without artificial layer splitting. Atomistic approaches (MD, AIMD, machine learning interatomic potentials) deliver molecular insight with ab initio accuracy across extended scales. We discuss key experimental benchmarks (differential capacitance, X-ray and vibrational spectroscopy) and identify promising directions: hybrid quantum + mPB/cDFT schemes capturing electronic spillover and partial charge transfer, advanced force fields, and open capacitance databases. These advances point toward a unified multiscale framework for predictive modelling of electrochemical interfaces.