Electrodeposited MnO₂ Thin Film as High–Performance Electrode for Supercapacitor Application

This study presents a facile electrochemical deposition approach for synthesizing MnO2 thin films directly onto stainless steel (SS) substrates, yielding binder-free nanostructured electrodes for supercapacitor applications. The structural, morphological, and electrochemical characteristics of the deposited MnO2 films were systematically investigated using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), and Scanning Electron Microscopy (SEM). XRD analysis confirmed the formation of the amorphous birnessite δ-MnO2 phase, while FTIR spectra exhibited a characteristic Mn-O stretching vibration at 576 cm⁻¹. XPS spectra indicated the presence of Mn-O-Mn and Mn-O-H bonds, confirming the oxidation states of Mn in the thin film. The electrochemical performance was evaluated using cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) measurements in a 1M Na2SO4 electrolyte. The as-deposited MnO2 thin film demonstrated a remarkable specific capacitance of 439 F g⁻¹ at a current density of 0.5 mA cm⁻², along with a power density of 669 W kg⁻¹ and an energy density of 61.02 Wh kg⁻¹. The high electrochemical performance of the MnO2 thin film can be attributed to its nanostructured morphology and amorphous nature, facilitating efficient charge storage. These findings underscore the suitability of electrodeposited MnO2 as a promising electrode material for next-generation supercapacitors.