DFT-AIMD simulations were performed using CP2K with the Perdew-Burke-Ernzerhof (PBE) exchangecorrelation functional , Grimme D3 dispersion corrections , and Goedecker-Teter-Hutter (GTH) pseudopotentials (O: GTH-PBE-q6, H: GTH-PBE-q1, Pt: GTH-PBE-q10) . A hybrid Gaussian and planewave approach was employed with a 400 Ry cutoff and Γ point sampling. Classical MD simulations were conducted in LAMMPS , with Pt atoms modeled using Lennard-Jones parameters from Heinz et al. Electrostatics were handled via the Particle-Particle Particle-Mesh (PPPM) method with an 8 Å cutoff. The comparison of capacitance values for different Gaussian widths is presented in Fig. . These results align with Serva et al. (Fig. ), demonstrating that increasing the Gaussian width enhances capacitance. However, potential profiles in our simulations (Fig. ) reveal that wider Gaussian distributions introduce unphysical opposite potential drops in the inner electrode region. To ensure metallicity and accurate electrostatics, we adopt a Gaussian width of 0.4 Å, minimizing Friedel oscillations and artifacts, consistent with the methodology of Siepmann and Sprik . By adopting this narrower width, our model ensures reliable electrostatic potential distributions and a consistent electric double-layer representation. Additional technical details regarding DFT and the FF simulations are reported in section S1 of the SI.