Question

The exchange current density and the electron transfer coefficient for the reaction Fe e Fee Pt at 25 "Care 2.5 * 10 cm and 0.42, respectively. (a) Determine at what current density to obtain an overpotential of 0.25 V according to the Butler Volmer equation. (b) What will be the overpotential at the same current density according to the Tafel equation?

Answer 1

For this question, we have to use the Butler Volmer equation and the tafel equation(that is derived from butler Volmer equation with large overpotential). In the answer, we are using the derived equation to solve the problem.

fest te Pezt Pye No Date of = F/RT Exchange current density i = 2.50 103 Acne Electron transfer coefficient, & 0 for onespotentional = 0.25V All to Butter volumer equation Net current density, j = ja je j = jo se!"-2) fh_ į kiną - j = 2.5 X10-A cui f = 38.94 vil 7-0.42) X 38.94 0.25 -0.42 X 38.9UXO e-0.42 2 ; = 2.5x103 Aumes et -4.08977 * j = 2.58 10-3 { 283.2415 - 0.01676? Acm² i = 708.06 x 103 Acri² 6 Ace to Tafel equation, aurrent duunity is given by- i i el 1-2)fn - eng= lujo + (1-4th > m1708.66 X10-3) = -2.5X10-3) + 11-0.42) 38.94 XY t en (708.06 X10-9) - In (2-5 X10-3) = (1-0.42) 38.9489 > ln (798-06) - 22:58x7 1) en (283:224) Vzy 2 1 3 0-25 V UUR 2.5 J 22:58 Bd. Au to Jafel plot, overpotential for the same cumeut de Is id aisOas