Molecular Dynamics Study of C-N Based Hybrid Supercapacitor

Abstract

In order to study the interfacial behavior between a nitrogen-doped carbon electrode and an aqueous KOH electrolyte, this study uses molecular dynamics (MD) simulations. Van der Waals interactions are described by the Lennard-Jones (LJ) potential model. Simulated under the NVT ensemble at 300 K, the system is made up of 3000 atoms, with carbon and nitrogen atoms forming the electrode regions and potassium ions (K⁺), hydroxide ions (OH⁻), and water molecules acting as the electrolyte.Significant structural correlations at the electrode– electrolyte interface are revealed by radial distribution function (RDF) analysis. Positive electrostatic adsorption is indicated by the nitrogen–K⁺ pair's strong RDF peak at 2.75 Å with g(r) ≈ 2.12. Additionally, there is a notable interaction between the carbon and OH⁻ ions, with a peak at 2.85 Å and g(r) ≈ 1.97, indicating surface-specific affinity. With an RDF peak for N–O_w interactions at 3.15 Å, water molecules show moderate structuring close to nitrogen sites. The system's dynamic behavior is further highlighted by mean square displacement (MSD) analysis. After 50 ps, the MSD values for potassium and hydroxide ions are 0.14 Ų and 0.12 Ų, respectively, indicating moderate mobility limited by interfacial forces. However, with MSD values less than 0.03 Ų, the electrode atoms (C, N) stay essentially immobile, confirming structural rigidity, which is crucial for electrochemical performance. The adsorption properties and ion transport behavior close to nitrogen-doped carbon surfaces are effectively captured by the LJ potential-based model. These discoveries confirm that these nanostructured materials are appropriate for advanced electrochemical energy storage and supercapacitor applications.