Potentiodynamic investigation of oxygen reduction reaction on polycrystalline platinum surface in acidic solutions: The effect of the polarization rate on the kinetic parameters

Abstract

The time of exposure of potentiodynamically polarized platinum electrode to the potentials of oxide formation was considered quantitatively as a factor of kinetics of oxygen reduction reaction (ORR) in acidic, HClo4 and H2So4 solution. In general, the enhancement of catalytic activity towards ORR was measured upon increasing sweep rate. The results were discussed in terms of the amount of oxide formed on platinum surface, which decreased upon increasing sweep rate. The scope of view was confirmed that the Tafel slope for ORR on oxide-free Pt amounts to 120 mV dec-1, while various values between 120 and 60 mV dec-1, reported often in the literature, are governed by the site blocking/surface reorganization processes. © 2012 by ESG.