Polypyrrole employed interfacial engineering of porous NiFe2O4/Ti3C2Tx hybridized triphasic freestanding films for high-performance flexible pseudocapacitors

Rational design of a unique hybrid derived from transition-metal oxides, known to possess high capacity but poor electronic conductivity, with two-dimensional (2D) MXenes, known to possess metallic conductivity but with 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 hybrid 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 MNF10@PPy hybrids to improve energy storage pseudocapacitive electrodes for flexible devices.