Investigation of aging procedure on electrochemical impedance spectroscopy response of commercial ۲۰ wt% Pt/C catalyst

Electrochemical impedance spectroscopy is one of the most conventional techniques, which byanalyzing the Nyquist and phase plot, as well as extracting important parameters through fitting with equivalent circuits, it is possible to determine the resistance and activity of the catalyst for electrochemical reaction. In this work, the impedance spectrum of Pt/C catalyst a in kinetic region, the ohmic region, and the diffusion limited region of the polarization curve is investigated at theelectrode rotation rate of ۱۶۰۰ rpm. Polar resistance (RP) and ohmic resistance (Rs) are the most important elements obtained from fitting impedance plots with Randles equivalent circuit; theresults have shown that polar resistance around ۷۵۰ mV is under charge transfer resistance (Rct),while at potentials lower than ۷۵۰ mV is more under mass transfer resistance. In the simplest case,the Rp appears in the form of a semicircle at high frequencies in the high potentials of the kineticregion; this resistance is related to the entire electrode-electrolyte interface (۲). The nature of theelectrochemical impedance spectrum is determined by the constituents of the catalyst layer and the operating potential; for example, in the potentials of the kinetic region, the response of the thin layer of the Pt/C catalyst for the impedance spectrum is a semi-circle at high frequencies. Toperform such a test, the working electrode in ۳-electrode setup includes glassy carbon, ۲۰ wt% Pt/C catalyst, nafion solution ۵ wt% and ۹;۱ solvent (water: isopropyl). In this study, oxygen reduction reaction for commercial ۲۰ wt% Pt/C catalyst during aging tests is investigated using electrochemical impedance spectroscopy (EIS). This investigation has been done under theoperating potential of ۰.۸۲ V vs. RHE According to the results of fitting data (table), during theaging test, the charge transfer resistance is increased at the mentioned potential. So that the charge transfer resistance (Rct) has increased by ۴۲.۷% after ۱۰۰۰۰ cycles.