FE-SEM images of the synthesized sample by hydrothermal route involves conversion process from precursor nano rods to octahedron under different temperatures: (a, b) 120 °C; (c) 160 °C; (d) 180 °C; (e) 200 °C; and (f) TEM images of as-synthesized products at 200 °C. “Reprinted from Chemical Engineering Journal, 172(1), Ahmed, K. A., Peng, H., Wu, K., Huang, K., Hydrothermal preparation of nanostructured manganese oxides (MnOx) and their electrochemical and photocatalytic properties, 531-539, copyright (2011), with permission from Elsevier”.