3D Hierarchical Ti₃C₂T@PANI-Reduced Graphene Oxide Heterostructure Hydrogel Anode and Defective Reduced Graphene...

The practical application of supercapacitors (SCs) has been known to be restricted by low energy density, and zinc ion capacitors (ZICs) with a capacitive cathode and a battery-type anode have emerged as a unique technology that can effectively mitigate the issue. To this end, the design of electrodes with low electrochemical impedance, high specific capacitance, and outstanding reaction stability represents a critical first step. Herein, we report the synthesis of hierarchical Ti₃C₂T@PANI heterostructures by uniform deposition of conductive polyaniline (PANI) polymer nanofibers on the exposed surface of the Ti₃C₂T nanosheets, which are then assembled into a three-dimensional (3D) cross-linking framework by a graphene oxide (GO)-assisted self-convergence hydrothermal strategy. This resulting 3D Ti₃C₂T@PANI-reduced graphene oxide (Ti₃C₂T@PANI-RGO) heterostructure hydrogel shows a large surface area (488.75 F g^-1 at 0.5 A g^-1), outstanding electrical conductivity, and fast reaction kinetics, making it a promising electrode material. Separately, defective RGO (DRGO) hydrogels are prepared by a patterning process, and they exhibit a broad and uniform distribution of mesopores, which is conducive to ion transport with an excellent specific capacitance (223.52 F g^-1 at 0.5 A g^-1). A ZIC is subsequently constructed by utilizing Ti₃C₂T@PANI-RGO as the anode and DRGO as the cathode, which displays an extensive operating voltage (0-3.0 V), prominent energy density (1060.96 Wh kg^-1 at 761.32 W kg^-1, 439.87 Wh kg^-1 at 9786.86 W kg^-1), and durable cycle stability (retaining 67.9% of the original capacitance after 4000 cycles at 6 A g^-1). This study underscores the immense prospect of the Ti₃C₂T-based heterostructure hydrogel and DRGO as a feasible anode and cathode for ZICs, respectively.