When SC C is the space charge capacitance, e is the electron charge (F.cm -2 ),  is the dielectric constant of reaction, 0  is the vacuum permittivity, N is the number of donors, k is Boltzmann constant, T is the experiment temperature (K), and A is the surface area of electrode contact with the electrolyte (cm). E is the applied potential (V). The FB E is estimated by extrapolating a linear fit of the MS plot to obtain the x-intercept (V). c values are shown in Table .