Electrically coupled NiFe2O4/Ti3C2 hybrids with enhanced dielectric and energy storage performance

Abstract

NiFe2O4/Ti3C2 hybrid composites exhibit superior dielectric and pseudocapacitive properties, due to highly efficient interfacial charge transport. Conventional spinel ferrites suffer from intrinsically low electronic conductivity and limited rate capability, while pristine MXenes often exhibit restacking and insufficient dielectric response. The NiFe2O4/Ti3C2 hybrid bridges this gap by engineering conductive heterointerfaces that promote ultrafast electron delocalization, strong Maxwell–Wagner–Sillars interfacial polarization, and synergistic pseudocapacitive/redox activity. Consequently, the specific capacitance increased significantly from 143 to 503 F g−1 in the hybrid, indicating dominant surface-controlled redox kinetics with reduced diffusion limitations. Strong electrical coupling at the carbide–ferrite heterointerfaces is confirmed by low charge-transfer resistance and rapid electron mobility. Dielectric analysis shows an exceptionally high dielectric constant (ε′ ∼ 2.5 × 105) at low frequencies and high temperatures due to thermally activated polar accumulation and Ti3C2-induced micro-capacitors, as evidenced by depressed Cole–Cole arcs and R-CPE circuit elements. The AC conductivity obeys Jonscher's power law, with the exponent n decreasing systematically with temperature (0.893 ± 0.018 to 0.622 ± 0.014), confirming the short-range correlated barrier hopping mechanism driven by thermally activated hopping of localized carriers. These synergistic electrical-electrochemical effects make the NiFe2O4/Ti3C2 hybrid a promising candidate for next-generation electrochemical energy storage systems.