The inductive response at low frequencies was taken into account in all spectra. In this circuit, Rs is the solution resistance, R1 is the charge transfer resistance, CPE1 is the constant phase element describing the double layer capacitance, R2 is the resistance of surface oxide or adsorbates, and L is the inductance . The constant phase element (CPE) was used to assign the capacitive response of a non-uniform surface. The impedance of CPE can be expressed as: