Hydrothermally synthesised α-MnO₂ and β-MnO₂ nanorods for pseudocapacitor electrode applications

We investigated the electrochemical performances of α-MnO₂ and β-MnO₂ nanorods synthesised via hydrothermal route. The electrochemical properties of α- and β-MnO₂ evaluated utilising cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS) in 1 M KOH electrolyte revealed that the α-MnO₂ electrode exhibits a specific capacity of 743 C/g whereas β-MnO₂ electrode exhibited a specific capacity of 391 C/g for same current density of 3 A/g. Also, after 5000 cycles, α- MnO₂ exhibits a capacity retention of 80%, while β-MnO₂ shows 64% retention. The present work reports the enhanced pseudocapacitor electrode performance of α-MnO₂ over β-MnO₂. For practical application, synthesized α-MnO₂ and activated carbon were assembled in Swagelok-type cell to fabricate hybrid supercapacitor. The hybrid supercapacitor exhibits exceptional specific capacitance of 241.25 F g⁻¹, with excellent energy and power density of 85.77 Wh Kg⁻¹ and 1600 W Kg⁻¹ respectively.