Study of oxygen reduction reaction activity drop of Pt/C catalyst during aging cycles

Linear sweep voltammetry is one of the most conventional techniques, which by using it and extracting important activity parameters such as onset potential (Eonset), half-wave potential (E۱), and Tafel slope in three kinetic, ohmic, and diffusion limited current density, it is possible to determine the activity of the catalyst to use the oxygen reduction reaction (ORR). Also, by using aging tests, it is possible to evaluate the stability and activity loss of catalyst Pt/C for the ORR during the aging tests (۱-۲). In this study, the effect of catalyst aging cycles on Pt/C catalyst degradation is evaluated using LSV technique. This investigation is done in three steps before the aging tests, after the ۵۰۰۰th cycle of aging and after ۱۰۰۰۰th cycle of aging. 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); According to Fig. ۱-a, which shows the polarization curves of Pt/C catalyst activity during the aging test, the activity of the ORR is greatly reduced; according to the table۱, the onset potential and half-wave potential during ORR after ۵۰۰۰th and ۱۰۰۰۰th cycles have shifted to lower values; Also, after ۵۰۰۰th and ۱۰۰۰۰th cycles, the diffusion limited current density has decreased at the same potentials. In addition, according to Fig.۱-b, which shows the Tafel plots of the three mentioned steps, and ۱۰۰۰۰ cycles, the Tafel slope has reached to the highest value (۹۹ mV/dec). The results show that after aging tests, the activity of the catalyst for the ORR has decreased, which can be due to the destruction of the catalyst layer.