Therefore, the 𝑅 𝑐𝑡 ′ versus current data were also fitted to a two-step BV model, assuming α1 = 0.5 and α2 = 3, to calculate the values of I0,n for each reaction step. The 2-step BV model fits the data more closely in the intermediate current range, yielding I0,1 = 7.37 mA cm -2 and I0,2 = 3.21 mA cm -2 . The contribution of each reaction step to the measured differential resistance (i.e., 𝑅 𝑐𝑡,𝑛 ′ ) can be calculated as a function of current from the fitted two-step BV model (Fig. ).