Synthesis of Ti ₃ C ₂ T _x(exf) @h‐BN@Co ₃ O ₄ Hierarchical Structure: An Active Cathode for High‐Performing Solid‐State Supercapacitor and Density Functional Theory Calculations

Herein, the synthesis of Ti 3 C 2 T x(exf) @h‐BN@Co 3 O 4 and its electrochemical performances as an active cathode material in a flexible all‐solid‐state asymmetric supercapacitor (ASC) is presented. A hierarchical heterostructure has been created by integrating nanometer‐thin exfoliated Ti 3 C 2 T x(exf) MXene sheets with a 2‐D layered hexagonal boron nitride (h‐BN) and immobilizing Co 3 O 4 nanorods on the surface. h‐BN and Co 3 O 4 offer rich redox features and highly conductive Ti 3 C 2 T x facilitates the charge transfer process. To prepare the anode of ASC, a spent tea‐derived porous carbon (PC) was used. An ASC device (Ti 3 C 2 T x(exf) @h‐BN@Co 3 O 4 //PC) was assembled with PVA‐KOH gel‐electrolyte. This device exhibited a specific capacitance of 105.8 F g −1 at a current density of 0.5 A g −1 , an energy density of 33.0 W h kg −1 at a power density of 375 W kg −1 , and retention of ≈90% of its initial capacitance and ≈85% of its Coulombic efficiency after 5000 charge‐discharge cycles. To gain an in‐depth understanding of the electronic band structure of Ti 3 C 2 @h‐BN@Co 3 O 4, computational investigations were carried out. The calculated value of quantum capacitance of Ti 3 C 2 @h‐BN@Co 3 O 4 was 59.16 μFcm −2 at 2.67 V (positive bias). This work highlights the exceptional performance and durability of Ti 3 C 2 T x(exf) @h‐BN@Co 3 O 4 ternary heterostructure and positions it as a highly promising candidate for next‐generation supercapacitors.