A comparative study on polyaniline degradation by an electrochemical quartz crystal impedance system: electrode and solution effects

摘要

By combining the piezoelectric quartz crystal impedance (PQCI) and electrochemical impedance spectroscopy (EIS) measurements, we conducted a comparative study on polyaniline (PANI) degradation in different media, HClO_4 and H_2SO_4, and on different piezoelectric quartz crystal (PQC) electrodes, Pt and Au. It is concluded that (1) the PANI film grown on an Au electrode is more stable than that on a Pt electrode; (2) the PANI degradation reaction abides by the zero-order kinetic law in HClO_4 with rate constants from 0.17 to 2.25 Hz s~(-1) on Pt and 0.16 to 0.83 Hz s~(-1) on Au, but the first-order kinetic law in H_2SO_4 with rate constants from 2.61 X 10~(-3) to 7.00 X 10~(-3) s~(-1) on Pt and 1.00 X 10~(-3) to 5.00 X 10~(-3) s~(-1) on Au at different ion concentrations. The contrary effects of ClO_4~- and SO_4~(2-) on PANI degradation may be understood from the Hofmeister series of anions; (3) the dissolution of the PANI film bulk, the increase of film porosity and the film attenuation occurred simultaneously during degradation via systematic analyses of the motional resistance (R_1)and electrochemical impedance spectra responses, etc.