Supramolecular Engineering of Ti ₃ C ₂ T _x MXene ‐Perylene Diimide Hybrid Electrodes for the Pseudocapacitive Electrochemical Storage of Calcium Ions

Abstract The rare combination of metallic conductivity and surface redox activity enables 2D MXenes as versatile charge storage hosts for the design of high‐rate electrochemical energy storage devices. However, high charge density metal ions including but not limited to Ca ⁺² and Mg ⁺² pose challenges such as sluggish solid‐state diffusion and also inhibiting the charge transfer across electrode‐electrolyte interfaces. In this work, free‐standing hybrid electrode architectures based on 2D titanium carbide‐cationic perylene diimide (Ti ₃ C ₂ T _x @ c PDI) via supramolecular self‐assembly are developed. Secondary bonding interactions such as dipole‐dipole and hydrogen bonding between Ti ₃ C ₂ T _x and c PDI are investigated by zeta potential and Fourier‐transformed infrared (FTIR) spectroscopy . Ti ₃ C ₂ T _x @ c PDI free‐standing electrodes show typical volumetric capacitance up to 260 F cm ⁻³ in Mg ²⁺ and Ca ²⁺ aqueous electrolytes at charging times scales from 3 minutes to a few seconds. Three‐dimensional (3D) Bode maps are constructed to understand the charge storage dynamics of Ti ₃ C ₂ T _x @ c PDI hybrid electrode in an aqueous Ca‐ion electrolyte. ,Pseudocapacitance is solely contributed by the nanoscale distribution of redox‐active c PDI supramolecular polymers across 2D Ti ₃ C ₂ T _x . This study opens avenues for the design of a wide variety of MXene@redox active organic charge hosts for high‐rate pseudocapacitive energy storage devices.