Whether it should be with respect to E (reference) or E (open circuit) ? And what is the potential value we need to put? Whether we should consider the onset potential from LSV or at 0V?
In EIS (Electrochemical Impedance Spectroscopy), the solution resistance should be measured at the open circuit potential (OCP) or equilibrium potential. The OCP is the potential of the working electrode in the absence of any external current flow, and it represents the potential at which there is no net transfer of electrons or charge between the electrode and the electrolyte.
The potential value for measuring the solution resistance can be determined experimentally by first measuring the OCP of the working electrode using a reference electrode. Once the OCP has been determined, the potential at which the EIS measurement should be conducted can be set to this value.
Regarding the potential value for LSV (Linear Sweep Voltammetry), the onset potential can be used to estimate the potential range over which the electrochemical reaction of interest occurs. However, for the measurement of solution resistance using EIS, the potential at which the measurement is conducted should be at the OCP, not necessarily at the onset potential determined from LSV. If you find this answer useful please follow my work on research gate.
The open circuit potential is the potential at which no current is flowing through the system, and the electrochemical reactions are at equilibrium. Measuring EIS at or near the OCP ensures that the solution resistance dominates the impedance response, minimizing the influence of other electrochemical processes such as charge transfer reactions or mass transport.
When you obtain an EIS plot (Nyquist or Bode plot), the solution resistance can be extracted from the high-frequency region of the plot. In a Nyquist plot, the solution resistance corresponds to the real part of the impedance (Z') at the highest frequencies, which is the intercept of the semicircle with the Z' axis. In a Bode plot, you can find the solution resistance by observing the impedance magnitude at the highest frequencies where the phase angle is close to zero degrees.
In a Bode plot, the impedance magnitude and phase angle provide information about the behavior of a circuit as the frequency of the input signal changes. The magnitude plot shows how the circuit responds to signals of different frequencies, while the phase plot shows the phase shift between the input and output signals.
At high frequencies, the impedance of capacitors and inductors becomes significant, and their reactance dominates over their resistance. This means that the impedance of the circuit is primarily determined by the reactance of the capacitors and inductors, rather than their resistance.
However, the resistance of the circuit is still important because it determines how much power is dissipated in the circuit. At high frequencies, the phase angle approaches zero degrees, which means that the circuit is mostly resistive and that the reactive components are not contributing much to the impedance.
Therefore, by observing the impedance magnitude at the highest frequencies where the phase angle is close to zero degrees, we can determine the value of the solution resistance of the circuit. This is the resistance that is responsible for dissipating most of the power in the circuit at high frequencies, and it can be used to calculate other circuit parameters, such as the power dissipated in the circuit, the voltage drop across the resistance, and the current flowing through the resistance.
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science