Structural and Electrochemical Insights into Ultrasonic Spray Pyrolysis-Derived Pure and Zn-Modified Mn3O4 for High-Performance Supercapacitors

In this study, Mn3O4 and Zn-modified Mn3O4 thin films are synthesized on glass substrates using ultrasonic spray pyrolysis. A comprehensive analysis is performed on their structural, optical, chemical, photoluminescent, and electrochemical properties. X-ray diffraction confirmed the formation of a tetragonal hausmannite phase, with peak shifts indicating lattice distortion due to Zn incorporation. Ultraviolet-Visible (UV-Vis) analysis showed a band gap increase from 2.00 to 2.51 eV with Zn doping, alongside reduced visible-region absorbance. X-ray photoelectron spectroscopy validated the substitution of Zn2+ ions and provided insight into the Mn and Zn oxidation states. Photoluminescence spectra indicated reduced radiative recombination upon doping. Electrochemical evaluations using galvanostatic charge-discharge, electrochemical impedance spectroscopy, and cyclic voltammetry demonstrated significant improvement in charge storage for Zn-doped electrodes. Capacitance values increased from 25 F g-1 (pure) to 93 F g-1 (Zn-doped) at 10 mV s-1, with a maximum value of 333 F g-1 observed for 2% Zn-doped Mn3O4 at 1 A g-1. The Zn additive enhanced both the charge transport and capacitive behavior, affirming its promise for energy-storage applications.