Influence of molar concentration on the morphology and electrochemical performance of binder-free Mn₃O₄ thin films in aqueous symmetrical supercapacitors

The current study reports a cost-effective hydrothermal method for binder-less synthesis of manganese oxide (Mn₃O₄) nanostructures on flexible stainless steel (SS) substrates, expected to enhance electrochemical performance for supercapacitor (SC) applications. By optimizing Mn molar concentrations, the Mn₃O₄ film (MO) with a 3 M concentration formed a porous structure with cauliflower-like morphology, beneficial for energy storage in aqueous electrolytes. Physicochemical characterization is used for the analysis of the MO samples. The electrode MO-0.3 exhibited a specific capacity of 1211C g⁻¹ at 0.99 A g⁻¹. An aqueous symmetric device (MO-0.3//KOH//MO-0.3 ASD) demonstrated a specific capacitance of 120.23F g⁻¹, a specific energy of 16.77 Wh kg⁻¹, and a specific power of 247.52 W kg⁻¹, with ∽89 % capacitance retention after 5000 cycles. These findings underscore the potential of MO electrodes for high-performance electrochemical energy storage, showcasing the efficacy of this material in supercapacitor applications.