High‐Energy‐Density Supercapacitors Based on High‐Areal‐Specific‐Capacity Ti 3 C 2 T x and a Redox‐Active Organic‐Molecule Hybrid Electrode

Abstract Photorechargeable supercapacitors are perfect energy storage devices, particularly for solar cells that output electricity only during sunshine hours. The lower energy density of supercapacitors is due to fewer redox‐active sites, poor electrolyte accessibility at the electrodes, and charge loss during charge transfer from solar cells to the supercapacitor. Here, an electrolyte‐accessible organic–inorganic hybrid electrode with synergistic pseudocapacitance of Ti 3 C 2 T x and high theoretical specific capacity CO active centers to enhance the energy density of the supercapacitor is proposed. Density functional theory (DFT) calculations show that the covalent cross‐linking of organic molecules changes the charge density redistribution of Ti 3 C 2 T x , enhances ion absorption and storage, and increases the energy density of the supercapacitors. Based on these DFT calculation results, hybrid electrodes are successfully prepared using p‐phenylene diisocyanate to covalently cross‐link pseudocapacitors Ti 3 C 2 T x with anthraquinone such as 1‐hydroxyanthraquinone (HA) or 1‐amino‐4‐bromoanthraquinone‐2‐sodium sulfonate (ABS). The Ti 3 C 2 T x ‐HA hybrid electrodes exhibit high areal specific capacity (2532.5 mF cm −2 ), excellent ion absorption storage capability, and long‐term stability. The asymmetric supercapacitor yields a decent area specific capacity (1686.72 mF cm −2 at 0.25 mA cm −2 ) and energy density (599.72 mWh cm −2 at a power density of 200 mW cm −2 ). These high‐energy‐density supercapacitors are coupled with perovskite solar cells to prepare photorechargeable supercapacitors with fast energy storage.