Effects of transition metal ions on the electrochemical performance of polypyrrole electrode

Three transition metal ions (Ni2+, Fe2+ and Cu2+)were chosen as dopants to fabricate PPy/M2+ (M:Ni2+, Fe2+ and Cu2+) electrodes by cyclic voltammetry on the stainless steel wire mesh. Fourier transform infrared, X-ray diffraction, Scanning electron microscopy and X-ray photoelectron spectroscopy techniques were employed to characterize the structure and morphology of PPy/M2+. The results prove that there are some changes in microstructure and valence of transition metal ions. Cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy tests in 1.0 mol L−1 HNO3 electrolyte in three-electrode system exhibit that the larger specific capacitance of PPy/M2+ electrodes are 517, 679 and 764 F g−1 at a current density of 5 mA cm−2 and the capacitance’ retention is 80.5, 82.7 and 83.8% after 1000 cycles. Besides, it was found that the different electrochemical properties of PPy/M2+ electrodes related to different ionic nature, such as ionic potential and ionic radius.