A Synergistically Integrated Spinel High-Entropy oxide@graphitic Carbon Nitride Nanocomposite Synthesized via a...

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)₃O₄, with graphitic carbon nitride (g-C₃N₄). Leveraging the unique cocktail effect, the multi-cation redox activity of HEO, and its plentiful reversible redox-active sites, the synthesized HEO@g-C₃N₄ 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-C₃N₄ nanocomposite matrix was thoroughly validated via complementary physicochemical characterizations, including XRD, SEM, FTIR, and XPS. The electrochemical measurements indicated that HEO@g-C₃N₄ nanocomposite shows an ultrahigh specific capacitance of 3263 F/g at a current density of 5 A/g. Furthermore, the hybrid HEO@g-C₃N₄ 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-C₃N₄ skeleton may facilitate the electron transport and electrolyte ion diffusion. Additionally, g-C₃N₄ can act as a structural buffer to mitigate volume expansion/contraction of HEO during charge-discharge cycling.