Understanding the\nImpact of the Morphology, Phase\nStructure, and Mass Fraction of MnO₂ within MnO₂/Reduced Graphene Oxide Composites for Supercapacitor Applications

Abstract

The electrochemical supercapacitor performance of MnO₂ is significantly influenced by the phase structure due to\nthe various\nstructural features of the different MnO₂ polymorphs that\ninclude tunnels or layered structures that can facilitate ion transport\nand intercalation. However, the effect of the crystal structure of\nMnO₂ within MnO₂/carbon composites has not been\nfully explored or understood. Herein, we have synthesized different\ncrystal structures of MnO₂ (α- and β-MnO₂) within MnO₂/reduced graphene oxide (rGO) composites\nby a hydrothermal process using various amounts of (NH₄)₂SO₄, followed by systematic structural characterization\nand electrochemical capacitance measurements. An excellent capacitance\nperformance of 403 F g^–1 was observed in α-MnO₂/sulfur and nitrogen codoped reduced graphene oxide (S,N-rGO)\ncomposites because of the interconnection between the conductive porous\n3D architectures of S,N-rGO and the α-MnO₂ nanorods.\nThis work highlights how the morphology, phase structure, and mass\nloading of MnO₂ within MnO₂/rGO composites directly\ninfluence the capacitance performance and rate capabilities, which\nprovides insight into the design of MnO₂-based composite\nmaterials for supercapacitor applications.