Study on the Effect of Annealing Process on Microstructure and Electrochemical Behavior of the Binary Mn-Ni Nano-Oxide Pseudocapacitor Synthesized by Anodic Deposition

In the present investigation, Mn-Ni binary nano-oxide was deposited by potentiodynamic method on stainless steel at room temperature and the effect of annealing process (at 200 oC for 6 h) on microstructure and electrochemical performance of the synthesized pseudocapacitor was studied. The results showed the significant effect of annealing process on increasing the capacitance and decreasing the charge transfer resistance of the electrode. Field Emission Scanning Electron Miscroscopy (FESEM) images depicted interconnected and random nano-flakes in the oxide film microstructure. Moreover, a partially crystallized structure consisting disorder hexagonal birnessite type phase was formed upon annealing in the deposited oxide film with about 10 %at Ni in composition. Based on the galvanostatic charge-discharge plots, the highest specific capacitance (384 F g-1) and specific energy (53 Wh kg-1) were found at specific current of 0.1 A g-1 for the annealed oxide electrode. Finally, cycle life test results at specific current of 10 A g-1 showed an excellent cyclability and an increase of about 23% in specific capacitance of synthesized pseudocapacitor after 5000 charge-discharge cycles in 1 M Na2SO4.