Morphology-Driven Electrochemical Performance of Mn2O3 Nanostructures for Supercapacitor and Water-Splitting Applications

Morphology engineering of electrode materials is a key strategy for optimizing electrochemical performance in energy storage and conversion applications. In this work, Mn2O3 with sphere, twin-sphere, dumbbell, and rod morphologies was synthesized via a hydrothermal method and systematically investigated for supercapacitor and electrocatalytic applications. Structural and surface analyses confirmed phase-pure cubic Mn2O3 with morphology-dependent surface area and porosity, where the twin-sphere structure exhibited the highest surface area (≈ 92 m2/g), average pore radius (4.06 nm), and pore volume (0.186 cm3/g). Electrochemical studies in 1 M KOH revealed mixed capacitive and diffusion-controlled charge storage. The twin-sphere morphology delivers superior specific capacitance (570 F/g at 10 mV/s, 383 F/g at 1 A/g) with excellent cycling stability (98% retention over 5000 cycles). From the oxygen evolution reaction (OER), Mn2O3-Dumbbell exhibits the lowest overpotential of 335 mV. In contrast, in the hydrogen evolution reaction (HER) measurements, Mn2O3-Twin Sphere demonstrates superior performance with a low overpotential of 189 mV at 10 mA/cm2. Electrochemical impedance spectroscopy further confirmed enhanced ion diffusion and reduced charge-transfer resistance. Overall, this study establishes a clear correlation between Mn2O3 morphology and electrochemical performance, providing valuable insights for the rational design of high-performance electrode materials for energy storage and water-splitting applications.