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<p>Activation energy is a well-known empirical parameter in chemical kinetics that characterises
the dependence of the chemical rate coefficients on the temperature and provides
information to compare the intrinsic activity of the catalysts. However, the determination and
interpretation of the apparent activation energy in multistep reactions is not an easy task. For
this purpose, the concept of degree of rate control is convenient, which comprises a
mathematical approach for analyzing reaction mechanisms and chemical kinetics. Although
this concept has been used in catalysis, it has not yet been applied in electrocatalytic systems,
whose ability to control the potential across the solid/liquid interface is the main difference
with heterogenous catalysis, and the electrical current is commonly used as a measure of the
reaction rate. Herein we use the definition of ‘degree of rate control for elementary step’ to
address some of the drawbacks that frequently arise with interpreting apparent activation
energy as a measure of intrinsic electrocatalytic activity of electrode. For this, an electrokinetic
model Langmuir-Hinshelwood-like is used for making numerical experiments and verifying the
proposed ideas. The results show that to improve the catalytic activity of an electrode
material, it must act upon the reaction steps with the highest normalised absolute values of
degree of rate control. On the other hand, experiments at different applied voltages showed
that if the electroactive surface poisoning process take place, changes in 𝐸𝑎𝑝𝑝 can not be used
to compare the catalytic activity of the electrodes. Finally, the importance of making
measurements at steady-state to avoid large errors in the calculations of apparent activation
energy is also discussed.
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On the relation between the activation energy for electron attachment reactions and the size of their thermal rate coefficients
