Improved capacitive behavior of electrochemically synthesized Mn oxide/PEDOT electrodes utilized as electrochemical capacitors

A sequential synthetic approach and a one-step method were adopted to synthesize Mn oxide/PEDOT electrodes through anodic deposition on Au coated Si substrates from aqueous solutions. In the former case, free standing Mn oxide rods (about 10 μm long and less than 1.5 μm in diameter) were first synthesized without a template through anodic deposition from a dilute solution of Mn acetate, then coated by electro-polymerization of a conducting polymer (PEDOT) giving coaxial rods. The one-step, co-electrodeposition method produced agglomerated Mn oxide/PEDOT particles. The electrochemical behavior of the deposits depended on the morphology and crystal structure of the fabricated electrodes, which were affected by the pH of electrolyte, deposition potential, current density and polymer deposition time. Structural characterization of as-deposited and cycled electrodes was conducted using XPS, SEM, TEM and AES.The Mn oxide/PEDOT coaxial core/shell electrodes prepared by the sequential method showed significantly better specific capacity and redox performance properties relative to both uncoated Mn oxide rods and co-electrodeposited Mn oxide/PEDOT electrodes. The best specific capacitance for Mn oxide/PEDOT rods produced sequentially was ∼285 F g−1 with ∼92% retention after 250 cycles in 0.5 M Na2SO4 at 20 mV s−1.