The flatband potentials of in aqueous electrolytes at different pH values were evaluated. The flatband potentials were measured by extrapolating the intercepts of Mott‐Schottky plots to the zero doping level. The capacitance values for the Mott‐Schottky plots were measured by relaxation spectrum analysis of the passive elements in the equivalent circuit of the electrolyte interface. The Mott‐Schottky plots used for evaluation of the flatband potential were linear over a potential range that exceeds 70% of the bandgap. It has been shown that when the doping distribution is homogeneous, the presence of surface states can be responsible for nonlinear Mott‐Schottky plots. The number, energy, and energy distribution of those states has been determined. The flatband potential of has been found to vary with pH at the rate of 60 mV/pH unit and is 100 mV more negative than the potential of reversible hydrogen electrode. The capacitance of the Helmholtz layer as a function of pH has also been determined.