Question

Consider the electrode reaction O + ne- = R. Under the conditions that CR* = CO* = 1 mM, ko = 10-7 cm/sec, anodic transfer coefficient (a) = cathodic transfer coefficient (c) = 0.5, and n = 1. CR* is the bulk concentration of R, CO* is the bulk concentration of O, ko is the constant that appears when we derive Butler-Volmer equation, and n is the number of electron.

a)Using Tafel equation and any spread-sheet program, draw log I i I vs. h curves (x-axis: overpotential (h) and y-axis: log I i I where i is the current density) with the current density up to 600 µA/cm² in both anodic and cathodic directions. Based on your spread-sheet plot, please provide its sketch below (You don’t need to turn in your spread-sheet plot. I just want its sketch).

b)Repeat the Part (a) using the anodic transfer coefficient (a_a) value of 0.9 and the cathodic transfer coefficient (a_c) value of 0.1

Please make a brief comment on the effect of changing the transfer coefficient (a) values on Tafel plots.

Answer 1