Mn-modified polypyrrole thin films for supercapacitor electrodes

• Thin film Mn-modified polypyrrole electrodes have been prepared using electrodeposition.
• Physical characterization shows a high area material is produced which is ideal for electrochemical capacitors.
• Their mechanism of electrochemical cycling has been examined using EQCM and EIS.
• Performance is superior to powdered materials in terms of specific capacitance and cycle stability.

Thin film Mn-modified polypyrrole (PPy) composite electrodes have been prepared by chronoamperometric electrodeposition and characterized in terms of their physico-chemical and electrochemical properties and performance. Analysis of the chronoamperometric data shows that electrodeposition of the thin film results in a relative increase in electrochemically active surface area of up to 30 times. This finding was supported by transmission electron microscopy (TEM), atomic force microscopy (AFM) and profilometry analysis of the films. Electrochemical quartz crystal microbalance (EQCM) studies have allowed for the direct determination of electrode mass, both during deposition and electrochemical performance evaluation, which has enabled analysis of electrode properties, including film growth (up to 26 μg/cm2), density (∼2 g/cm3), and the charge storage during electrochemical cycling, including the rates of mass uptake/removal with charge. The characteristics of the composite electrodes were compared with PPy-only electrodes throughout.