π-π stabilized cobalt tetraphenylporphyrin/MXene hybrids enable high-energy-density symmetric all-solid-state supercapacitors

To enhance the energy density of MXene-based supercapacitors, metal porphyrin (MPP) is intercalated between the highly conductive two-dimensional (2D) MXene layers, thereby improving the electrochemical performance of MPP and preventing the restacking of MXene layers during the charge-discharge process of the supercapacitor. In this work, a cobalt tetraphenylporphyrin (CoTPP)/MXene nanocomposite is prepared through a simple π-π stacking self-assembly. The successful intercalation of CoTPP between the MXene layers was confirmed by SEM, TEM, XRD, XPS, and BET. Furthermore, Density functional theory (DFT) calculation results demonstrate that the interaction between CoTPP and MXene stabilizes the composite structure. MXene provides a conductive network for CoTPP, reducing the reaction energy barrier during the charge-discharge process and accelerating ion and electron transport. The symmetric all-solid-state supercapacitor based on the CoTPP/MXene composite exhibits an energy density of 12.7 Wh kg −1 and a power density of 320 W kg −1 , which demonstrates remarkable cycling stability, maintaining a capacity retention of 96.67 % even after 20000 cycles under a high current density of 5 A g −1 . This work presents a straightforward and effective approach for synthesizing CoTPP/MXene with superior electrical conductivity, exceptional chemical stability, and outstanding energy storage performance, making it a promising candidate for supercapacitor electrodes.