Second, the low frequency region exhibit two regimes (slopes) as a function of the applied voltage: i) for V < 1.5 V, charges accumulate in the Helmholtz layer and the capacitive character of the impedance increases (larger |𝑍 𝑖𝑚𝑔 | for similar 𝑍 𝑟𝑒 ); ii) for V > 1.5 V, we observe a reduced slope value, originating from ion diffusion through the capacitive layer.