Influence of current collector on capacitive behavior and cycling stability of Tiron doped polypyrrole electrodes

In this work we demonstrate the feasibility of electrodeposition of adherent polypyrrole (PPy) films on Ni substrates using Tiron as an anionic dopant. Compared to other aromatic sulfonate dopants, Tiron offers the advantages of higher charge to mass ratio and chelating properties, which are beneficial for the efficient charge transfer during electropolymerization and fabrication of adherent films. The use of Ni plaque current collectors allows higher capacitance and higher PPy loading compared to Ni foil current collectors. Moreover, the use of Ni plaques allows significant improvement in capacitance retention at high scan rates. The problem of poor cycling stability of PPy films on Ni foil current collectors is successfully addressed by the use of Ni plaques. The electron microscopy studies and impedance spectroscopy measurements during cycling provide an insight into the factors, controlling capacitance retention. The results indicate that for pure PPy electrodes the mass normalized specific capacitance of 339–451 F g−1 and area normalized specific capacitance of 0.4–0.95 F cm−2 can be achieved for material loadings of 0.84–2.80 mg cm−2. The PPy electrodes formed on Ni plaque current collectors are promising for applications in electrochemical supercapacitors.