Temperature‐dependent synthesis of Mn ₃ O ₄ nanostructures by microwave irradiation method for high‐performance supercapacitors

Abstract

Summary Nanostructured Mn3O4 electrodes were synthesized via a simple and rapid one‐step microwave irradiation route, using manganese (II) nitrate hexahydrate and hydrazine hydrate. Four different morphologies (plate‐like, hexagonal‐like, rice‐like, and sphere‐like) were obtained by changing the reaction temperature such as 125°C, 150°C, 175°C, and 200°C (denoted as Mn‐125, Mn‐150, Mn‐175, and Mn‐200). Various analytical techniques such as X‐ray diffraction, Brunauer‐Emmett‐Teller, Raman, X‐ray photoelectron spectroscopy, scanning electron microscope, and high‐resolution transmission electron microscopy analysis were utilized to characterize the physicochemical properties of the prepared electrodes. The average crystallite sizes of the Mn‐125, Mn‐150, Mn‐175, and Mn‐200 samples were ~32.3, ~28.8, ~31.7, and ~28.9 nm, respectively. To evaluate the electrochemical properties of the Mn3O4 nanostructures for supercapacitors, cyclic voltammetry and galvanostatic charge/discharge measurements were performed. Remarkably, the hexagonal‐like Mn3O4 electrode showed a higher specific capacitance of 449.98 F g−1 at a lower current density of 1 A g−1 and showing outstanding cyclic permanence (95% capacitance retention 5000 cycles) than the other nanostructures.