Reconsideration of the quantitative characterization of the reaction intermediate on electrocatalysts by a rotating ring-disk electrode: The intrinsic yield of H2O2 on Pt/C

To solve the problem of the catalyst-loading-effect on quantifying the reaction intermediates on the surface of electrocatalysts with a rotating ring-disk electrode, we studied the formation of hydrogen peroxide in the oxygen reduction reaction on Pt/C with various sample loadings and then proposed an extrapolation model for measuring the intrinsic yield of H2O2, which can quantitatively reflect the characteristics of the surface of a given catalyst. In the extrapolation model, the catalyst loading effect can be compensated by taking the catalyst loading-dependent probability of the re-adsorption + further reaction of the desorbed H2O2 into consideration. The core concept in this extrapolation model is that the probability of the re-adsorption + reaction of the desorbed H2O2 becomes zero if there is no other active site available (i.e., at the extrapolated hypothetical point of zero catalyst loading) for re-adsorption of the desorbed H2O2. The intrinsic yield of H2O2 by extrapolation was much higher than that measured by the conventional model, in which the re-adsorption + reaction of the desorbed H2O2 is not considered, and thus the catalyst loading-dependent apparent yield of H2O2 does not properly reflect the intrinsic characteristics of the surface of a given catalyst. (C) 2010 Elsevier Ltd. All rights reserved.