A Synergistically Integrated Spinel High‐Entropy oxide@graphitic Carbon Nitride Nanocomposite Synthesized via a Facile Route for a High‐Performance Supercapacitor Electrode

ABSTRACT In this study, we report the rational strategy and facile route of a hybrid nanocomposite by integrating spinel‐structured high‐entropy oxides (HEO), such as (CrMnFeCoNi) 3 O 4 , with graphitic carbon nitride (g‐C 3 N 4 ). Leveraging the unique cocktail effect, the multi‐cation redox activity of HEO, and its plentiful reversible redox‐active sites, the synthesized HEO@g‐C 3 N 4 nanocomposite shows promise as an advanced supercapacitor (SC) electrode material. This synergistic integration can address the intrinsic limitations of HEOs, including poor electrical conductivity, inadequate structural stability/durability during repeated charge–discharge cycles, and restricted charge transfer kinetics. The intimate interfacial integration of the as‐made HEO@g‐C 3 N 4 nanocomposite matrix was thoroughly validated via complementary physicochemical characterizations, including XRD, SEM, FTIR, and XPS. The electrochemical measurements indicated that HEO@g‐C 3 N 4 nanocomposite shows an ultrahigh specific capacitance of 3263 F/g at a current density of 5 A/g. Furthermore, the hybrid HEO@g‐C 3 N 4 nanocomposite achieved an energy density of 408 J/g at around a power density of 1.086 KW/g. In comparison, pristine HEO shows 1652 F/g at 5 A/g, confirming that adding the g‐C 3 N 4 skeleton may facilitate the electron transport and electrolyte ion diffusion. Additionally, g‐C 3 N 4 can act as a structural buffer to mitigate volume expansion/contraction of HEO during charge–discharge cycling.