Polypyrrole employed interfacial engineering of porous NiFe₂O₄/Ti₃C₂T_x hybridized triphasic freestanding films for high-performance flexible pseudocapacitors

Rational design of a unique hybrid derived from transition-metal oxides, possessing high capacity but poor electronic conductivity, with two-dimensional (2D) MXenes, owning metallic conductivity but limited capacity and instability in aqueous electrolytes, is expected to produce innovative electrode materials for supercapacitor. In this study, we fabricated a free-standing triphasic composite film of NiFe₂O₄ pillared Ti₃C₂T_x encapsulated with polypyrrole (MNFx@PPy). This composite combined merits from large redox capacity of NiFe₂O₄ and high conductivity of Ti₃C₂T_x to operate within a voltage window of 1.2 V in 2.0 M H₂SO₄ electrolyte. The MNF10@PPy electrode had a specific capacity of 706.6 mAh·g⁻¹ at 1.0 A·g⁻¹, with 81.13 % retention at a high current density of 20 A·g⁻¹. The integration of PPy enhanced interfacial contact of the components which leads to upsurge in electrochemical performance and stability of the tri-component system. When the fabricated asymmetric flexible supercapacitor (MXene@PPy//MNF10@PPy) was assessed with broad 1.6 V, a complimentary potential window of both electrodes, the device offered 37.49 Wh·kg⁻¹ energy density at a power density of 3879 W·kg⁻¹. This study underscores the synergetic potential of the MNF10@PPy composite to improve energy storage pseudocapacitive electrodes for flexible devices.