Nanostructured manganese oxide films were obtained by electro-oxidation of manganese films electrodeposited at two typical cathodic currents of 65 mA cm-2 (EDM-65 oxide) and 150 mA cm-2 (EDM-150 oxide) from sulfate solutions with additives. Obtained Mn oxide films were studied by scanning electron microscope, X-ray photoelectron spectroscopy, cyclic voltammetry and AC impedance. SEM study revealed that the Mn oxide films were mesoporous nanostructures on the EDM-150 oxide surface, while the EDM-65 oxide coating is homogeneous and compact. XPS results indicate that EDM-150 oxide had a higher content of anhydrous Mn oxide and structure water, which means that it had more anhydrous characteristics as compared to EDM-65 oxide. It was shown that porous nanostructured films showed good capacitive behavior for applications in electrochemical supercapacitors. The porous nanostructured films prepared at 150 mA cm-2 showed higher specific capacitance (SC) compared to the SC of the EDM-65 oxide films. The highest SC of 148 F g-1 in a voltage window of 0.8 V was obtained in 0.1 M Na2SO4 solutions at a scan rate of 25 mV s-1.
On the Origin of the OER Activity of Ultrathin Manganese Oxide Films
