Effect of hydrothermal temperature on the structural and electrochemical properties of MnO2-based supercapacitors

Hydrothermally synthesized manganese dioxide (MnO₂) has attracted significant attention in supercapacitor applications due to its exceptional electrochemical properties. This research systematically explores the influence of hydrothermal temperatures of 105 °C (M1), 120 °C (M2), and 150 °C (M3) on the structural and electrochemical characteristics of MnO₂-based supercapacitors. From field effect scanning electron microscopy (FESEM) images, the average diameter of MnO₂ nanorods is 139 ± 3 nm, 140 ± 5 nm, and 156 ± 3 nm for M1, M2, and M3. The crystalline quality of MnO₂ increases by increasing the hydrothermal temperature (M3 sample). Shifting the Raman peak from 637 to 654 cm⁻¹ is observed due to the enhancement in crystallinity and nanorod size in the M3 sample. Higher surface area for smaller nanorods (M1) is also confirmed by the BET (Brunauer–Emmett–Teller) technique. At the scan rate of 10 mV/s, the specific capacitance obtained is 142 (M1), 135 (M2), and 131 (M3) F/g. By elucidating the intricate relationship between hydrothermal temperature and the resultant MnO₂ properties, this study provides valuable insights for optimizing the synthesis conditions to enhance the performance of MnO₂-based supercapacitors.