EIS Flashcards
1
Q
Advantages of EIS over dc techniques
A
- Use of very small excitation amplitudes (minimal perturbation)
- Information on both electrode capacitance and resistance
- Polarisation and solution resistance can be separately resolved
2
Q
What is EIS?
A
- Three electrode cell
- working electrode (electrode of interest), counter electrode and a reference electrode
- polarization applied by potentiostat ac sine wave of small amplitude
- ac current detected using two phase sensitive detectors in a quadrature
- by knowing potential amplitude and the ac current in phase and 90’ out of phase, the impedance of the working electrode can be described completely as a function of the frequency
3
Q
What is impedance?
A
- For ac theory where frequency is non zero, E^=I^ x Z which is analagous to V=IR
- Impedance (Z) is the equivalent of resistance
- resistor and capacitors impede the flow of electrons in an ac circuit
4
Q
Impedances in series
A
- Impedances added together
- Dominated by the largest individual impedance
5
Q
Impedances in parallel
A
- Impedances added reciprocally
- Dominated by the smallest individual impedance
6
Q
Impedance plot analysis
A
-Perform measurements on the circuit and analyse the resulting impedance plot
7
Q
Advantages of Bode plot over Nyquist
A
- Since frequency appears on one of the axes its easy to understand from plot how impedance depends on frequency
- Use of log frequency allows a wide freq range
- This is and advantage when impedance depends strongly on the frequency
8
Q
Resistors
A
Z = R
9
Q
Capacitors
A
Z = -j/wc
