Morphological tuning of MnO2 via pH-controlled hydrothermal synthesis for high-performance energy storage

In this work, pH-controlled hydrothermal synthesis was used to create MnO 2 nanostructures with specific structural, morphological, and electrochemical characteristics suitable for supercapacitor applications. Three alkaline pH levels, 8, 10, and 12, were used to create MnO 2 samples, which helped them study how alkaline pH impacts phase changes and charge-storage capabilities. XRD showed that the produced pure α-MnO 2 at both pH 8 and pH 10, while they obtained mixed-phase MnO 2 at pH 12. FESEM showed that pH changes cause morphological shift from entangled nanorods to spherical nanoparticles. The MnO 2 electrode created at pH 10 showed maximum specific surface area of 43.54 m 2 g −1 , which resulted in the same electrochemical performance as it produced a specific capacitance of 432 F g −1 at 0.5 A g −1 . The pH 8 sample produced the maximum capacitance of 505.14 F g −1 , while pH 12 electrode maintained 97.56% capacitance after 2000 cycles to demonstrate better cycling stability. It showed that pH modulation functions as an efficient method to enhance MnO 2 electrodes.