Intrinsic electrocatalytic activity is the ratio between the steady state coverage of reaction intermediates and their surface lifetimes. Thus, electrocatalytic activity is promoted by either increasing the steady state coverage of reaction intermediates, reducing their surface lifetimes, or some combination of both. Unfortunately, there is a lack of techniques for measuring these parameters. This manuscript demonstrates that these parameters can be quantified simultaneously by performing steady state isotopic transient kinetic analysis (SSITKA). SSITKA is performed by rapidly changing the isotopic composition of the reactant and measuring the isotopic transient of the corresponding product using a mass spectrometer. The observed product isotopic transient is used to calculate the coverage of intermediates and their surface lifetimes. Electrochemical SSITKA (eSSITKA) is demonstrated and validated using methanol (MeOH) oxidation to CO2 over Pt as a test reaction. The insights provided by these measurements are leveraged to explain the origins of the potential-dependent rate of MeOH oxidation in the low overpotential regime. This technique can be used to investigate any electrochemical reaction or electrocatalyst material that evolves a volatile product. Thus, this method is broadly applicable to the field of electrocatalysis and will facilitate the elucidation of a variety of different electrocatalytic phenomena.
Circelli et al. (Thu,) studied this question.