Fourier transform faradaic admittance measurements: I. Demonstration of the applicability of random and pseudo-random noise as applied potential signals
✍ Scribed by Sam C. Creason; Donald E. Smith
- Book ID
- 104149195
- Publisher
- Elsevier Science
- Year
- 1972
- Weight
- 362 KB
- Volume
- 36
- Category
- Article
- ISSN
- 0022-0728
No coin nor oath required. For personal study only.
✦ Synopsis
Faradaic admittance (or impedance) measurements are concerned with characterizing the property of the electrochemical cell defined in the frequency domain by the expression 1,2
where Af(co) is the faradaic admittance, If(co) is the faradaic current and E(co) is the potential across the electrical double-layer. Because the various frequency domain quantities in eqn. (1) contain both amplitude and phase characteristics, i.e., they are representable as complex numbers, it is more convenient in practice to utilize the alternative form 2-4
where E*(co) is the complex conjugate of E(co). This formulation confines all phase information to the numerator. E(co)E*(co) is the auto power spectrum of the potential applied across the double-layer, and If(co)E*(co) is the cross power spectrum 2-4 of the potential and faradaic current signals. Most experimental studies construct the frequency domain profile of Af(co) from point-by-point assessment of the response at different frequencies using pure sinusoidal applied potential signals***. However, eqn.( ) is not restricted to sinusoidal test signals. In fact, it is applicable to any generalized test signal, ~ 'NSF Trainee, 1971-1972; NDEA Fellow, 1970-1971. ~rA'To whom correspondence should be addressed. "*'~r~In most reports (not the present one) E(CO) and If (co) are not directly observable, but must be calculated from the working-reference electrode potential difference and total cell current by correcting for ohmic potential drop and double-layer charging current lo.