Whether the alpha value should be lower for an reaction?
If we compare the alpha values of similar reactions happening at different electrode surfaces (in a similar electrolyte, reduction), the alpha value should be smaller.
The transfer coefficient is very significant in HET kinetics especially when you are simulating CVs. Actually, both alpha and k (HET rate constant) are considered kinetic parameters. Alpha is a measure of the symmetry of the electron transfer energy barrier. In other words, it measures the position of the transition state between reactants and products in a HET reaction. A value of 0.5 is commonly assumed but typical values are between 0.3 and 0.7. From my understanding, all things been equal, a low alpha means sluggish kinetics. See chapter 3 of Electrochemical methods text book by Bard and Faulkner.
read the book by AKN Reddy and JOMBockris chapters 7-8
if you can access read Paul DELAHAY book
It's traditionally interpreted as the position of the potential energy maximum between the reactant and product, typically around 0.5, an indication of how symmetrical the potential energy barrier to electron transfer is. However, in practice, it can be potential dependent and there are some interesting interpretations being explored by Richard Compton that merit attention: Chem. Soc. Rev., 2013, 42, 4894-4905; Journal of Electroanalytical Chemistry 672, 12012, Pages 45–52
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