This study investigates the impact of the negative electrode based on various Fe₂O₃/N-doped reduced graphene oxide (N-rGO) composites on the electrochemical performance of an asymmetric supercapacitor coupled with MnO₂/N-rGO positive electrode. The amount of Fe₂O₃ in the composite affects the charge storage capability and stability when operating in a neutral aqueous electrolyte.

This study presents all-pseudocapacitive asymmetric supercapacitors (ASCs) operating in a neutral aqueous electrolyte. Hydrothermal approach is selected for the synthesis of the active electrode materials for ASC. Fe₂O₃ and N-doped reduced graphene oxide (N-rGO) composites are used for negative electrode, while MnO₂ and N-rGO composite is used for the positive electrode. The Fe₂O₃ content in the binary composite influences the porosity, morphology, and surface chemistry of the negative electrode material, which further impacts electrochemical performance and cyclic stability of the assembled ASCs. The studies show that graphene-based composites used as a negative electrode should exhibit appropriate porous structure in order to prevent undesired parasitic side reactions. The fabricated ASCs deliver high energy density up to 25.3 Wh kg⁻¹ density at a power density of 205 W kg⁻¹ when operated at 2 V in 1 M Na₂SO₄. The most stable configuration maintains almost 94% of the initial capacitance after 10 000 charge–discharge cycles. These components demonstrate the potential to fabricate environment-friendly, efficient, and reliable energy storage devices when combined in the proposed configuration with binary Fe₂O₃ (FNG) and MnO₂ (MNG) composites and a neutral aqueous electrolyte.