Handbook of Electrochemical Impedance Spectroscopy DISTRIBUTED and MIXED IMPEDANCES LEPMI J.-P. Diard, C. Montella Hosted by Bio-Logic @ www.bio-logic.info September 7, 2015
Handbookof
Electrochemical Impedance Spectroscopy
DISTRIBUTEDand
MIXED IMPEDANCES
LEPMIJ.-P. Diard, C. Montella
Hosted by Bio-Logic @ www.bio-logic.info
September 7, 2015
Contents
1 Introduction 51.1 Lumped vs. distributed systems . . . . . . . . . . . . . . . . . . . 5
1.1.1 Lumped systems . . . . . . . . . . . . . . . . . . . . . . . 51.1.2 Distributed systems . . . . . . . . . . . . . . . . . . . . . 51.1.3 Mixed lumped-distributed systems . . . . . . . . . . . . . 5
1.2 Examples in electrochemistry . . . . . . . . . . . . . . . . . . . . 51.2.1 Lumped systems . . . . . . . . . . . . . . . . . . . . . . . 51.2.2 Distributed systems . . . . . . . . . . . . . . . . . . . . . 61.2.3 Mixed lumped-distributed systems . . . . . . . . . . . . . 6
2 Impedance containing th√
S√S
9
2.1th
√S√
S. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1.1 Electrochemical reaction . . . . . . . . . . . . . . . . . . . 92.1.2 Electrochemical impedance . . . . . . . . . . . . . . . . . 92.1.3 Reduced impedance . . . . . . . . . . . . . . . . . . . . . 92.1.4 Graphs of the reduced impedance . . . . . . . . . . . . . . 92.1.5 Pole-zero map . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2th
√S√
S
1 + α th√
S√S
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.2.1 Electrochemical reaction . . . . . . . . . . . . . . . . . . . 112.2.2 Reduced Faradaic impedance . . . . . . . . . . . . . . . . 112.2.3 Nyquist diagrams . . . . . . . . . . . . . . . . . . . . . . . 11
2.3
(1 + α th
√S√
S
)th
√S√
S
1 + β th√
S√S
. . . . . . . . . . . . . . . . . . . . . . . . . 12
2.3.1 Electrochemical reaction . . . . . . . . . . . . . . . . . . . 122.3.2 Reduced concentration impedance . . . . . . . . . . . . . 122.3.3 Nyquist diagrams . . . . . . . . . . . . . . . . . . . . . . . 12
3 Mixed impedance 15
3.1th
√S√
S
1 + α S. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.1.1 Pole-zero map . . . . . . . . . . . . . . . . . . . . . . . . . 153.1.2 Nyquist diagrams . . . . . . . . . . . . . . . . . . . . . . . 15
3
4 CONTENTS
3.21 + α th
√S√
S
1 + β S. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.2.1 Electrochemical reaction: Volmer-Heyrovsky (V-H) . . . . 193.2.2 Reduced concentration impedance of adsorbed
species . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193.2.3 Nyquist diagrams . . . . . . . . . . . . . . . . . . . . . . . 19
3.31
1 + α S + β S th√
S√S
. . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.3.1 Electrochemical reaction: catalytic copperdeposition . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.3.2 Reduced concentration impedance of adsorbed species . . 213.3.3 Nyquist diagrams . . . . . . . . . . . . . . . . . . . . . . . 21
3.4S th
√S√
S
1 + α S + β S th√
S√S
. . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.4.1 Electrochemical reaction: catalytic copperdeposition . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.4.2 Reduced concentration impedance of solublespecies Cl− . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.4.3 Nyquist diagrams . . . . . . . . . . . . . . . . . . . . . . . 24
3.51 + α th
√S√
S
1 + β S + γ S th√
S√S
. . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.5.1 Electrochemical reaction: E-EAR reaction . . . . . . . . . 263.5.2 Reduced concentration impedance of adsorbed species . . 263.5.3 Nyquist diagrams . . . . . . . . . . . . . . . . . . . . . . . 26
3.6(1 + α S) th
√S√
S
1 + β S + γ S th√
S√S
. . . . . . . . . . . . . . . . . . . . . . . . . . 29
3.6.1 Electrochemical reaction: E-EAR reaction . . . . . . . . . 293.6.2 Reduced concentration impedance of soluble
species R . . . . . . . . . . . . . . . . . . . . . . . . . . . 293.6.3 Nyquist diagrams . . . . . . . . . . . . . . . . . . . . . . . 29
A Some rational fractions in√
S 33A.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33A.2
11 +
√S
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
A.31
1 + (√
S)3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
A.41 + (
√S)2√
S (1 + α(√
S)2). . . . . . . . . . . . . . . . . . . . . . . . . . . 35
A.51 − (
√S)2√
S (1 − α(√
S)2). . . . . . . . . . . . . . . . . . . . . . . . . . . 35
B Reactions involving adsorbed and soluble species 39
Bibliography 42
Chapter 1
Introduction
1.1 Lumped vs. distributed systems
1.1.1 Lumped systems
The transfer functions of systems modeled by ordinary differential equations,often called lumped-parameter systems, are rational functions (i.e. a ratio oftwo polynomials in s, the Laplace variable) [1, 2].
1.1.2 Distributed systems
The transfer functions of distributed parameter systems are irrational functions.The analysis of rational and irrational transfer functions differ in a number ofimportant aspects. The most obvious differences between rational and irrationaltransfer functions are the poles and zeros. Irrational transfer functions oftenhave infinitely many poles and zeros [2].
1.1.3 Mixed lumped-distributed systems
The transfer functions of mixed lumped-distributed systems contain rationaland irrational functions in s.
1.2 Examples in electrochemistry
1.2.1 Lumped systems
Faradaic impedance Zf and impedance Z of electrochemical adsorption reaction(EAR) are lumped systems [3,4]. Eq. (1.1) is a rational fraction in s (1).
Z(s) =1 + RctCadss
s ((Cdl + Cads) + sRctCdlCads)(1.1)
Z(s) = K1 + α s
s (1 + β s),K =
1Cdl + Cads
, α = RctCads, β =RctCdlCads
Cdl + Cads(1.2)
1Replacing a capacitor, for example Cdl, by a CPE [5] transforms a lumped impedance ina distributed impedance. This case is not subsequently envisaged.
5
6 CHAPTER 1. INTRODUCTION
Rct
Cdl
Cads
Figure 1.1: Equivalent circuit for electrochemical adsorption reaction (EAR).
1.2.2 Distributed systems
The Faradaic impedance of a corroding electrode with mass transfer limitation(Fig 1.2)) is a rational fraction in
√s, i.e. an irrational fraction in s.
Zf(s) =R σ
σ + R√
s(1.3)
Zf(s) =K
1 + α√
s, K = R, α =
R
σ(1.4)
Rct
Figure 1.2: Equivalent circuit for a corroding electrode with mass transfer limitation.W: Warburg element for semi-innite linear diffusion [6].
1.2.3 Mixed lumped-distributed systems
The impedance of the Randles equivalent circuit [4, 6, 7] (Fig. 1.3) is a mixedlumped and distributed system:
Z(s) =Rct + Rd
th√
τds√
τds
1 + RctCdl s + Cdl s Rdth
√τds
√τds
(1.5)
Z(s) = K
1 + αth
√τds
√τds
1 + β s + γ sth
√τds
√τds
, K = Rct, α =Rd
Rct, β = RctCdl γ = CdlRd
(1.6)
1.2. EXAMPLES IN ELECTROCHEMISTRY 7
∆
Rct
Cdl
Figure 1.3: Randles equivalent circuit for a redox reactions studied on a rotating diskelectrode. Wδ: bounded diffusion impedance [6].
Chapter 2
Impedance containing th√
S√S
2.1th
√S√
S
2.1.1 Electrochemical reaction
Redox reaction [4,8, 9]:
O + e ↔ R
studied on a rotating disk electrode with mass transfer limitation.
2.1.2 Electrochemical impedance
ZWδ(s) = Rd
th√
τ s√τ s
(1) (2.1)
2.1.3 Reduced impedance
ZWδ(s) = Rd
th√
τ s√τ s
⇒ Z(S) =ZWδ
(s)Rd
=th
√S√
S, S = τ s = Σ + iu (2.2)
2.1.4 Graphs of the reduced impedance
2.1.5 Pole-zero map
Infinite product expansion [12–16]:
th√
S√S
=1
1 +4S
π2
∞∏k=1
1 +S
(k π)2
1 +4S
((2 k + 1) π)2
= P∞ (2.3)
Thanks to Eq. (2.3)1This expression could be replaced by a more accurate one [10, 11]. This case is not
subsequently envisaged.
9
10 CHAPTER 2. IMPEDANCE CONTAINING TH√
S√S
• infinity of interlaced real poles and zeros (Fig. 2.1).
sp = −14((2k + 1) π)2, k = 1 · · ·∞ (2.4)
sZ = −(k π)2, k = 1 · · ·∞ (2.5)
Figure 2.1: Pole-zero map ofth
√S√
s.
Figure 2.2: 3D plot of the modulus ofth
√S√
S.
2.2.
TH√
S√S
1 + α TH√
S√S
11
2.2
th√
S√S
1 + α th√
S√S
2.2.1 Electrochemical reaction
Corroding electrode with mass transfert limitation:
M → Mn+ + n e−
O2 + 4 e− + 4 H+ → 2 H2O
2.2.2 Reduced Faradaic impedance
Z(S) =
th√
S√S
1 + αth
√S√
S
, uc1 = 2.54, uc2 = α2 (2.6)
2.2.3 Nyquist diagrams
Figure 2.3: Nyquist diagrams calculated from Eq. (2.6). Red dots : uc1 = 2.54, blackdots : uc2 = α2.
• uc1 ≫ uc2, 2.54 ≫ α2 ⇒ quarter of a lemniscate,
• uc1 ≪ uc2, 2.54 ≪ α2 ⇒ quarter of a circle (see Annex A.2).
12 CHAPTER 2. IMPEDANCE CONTAINING TH√
S√S
2.3
(1 + α th
√S√
S
)th
√S√
S
1 + β th√
S√S
2.3.1 Electrochemical reaction
EE reaction [17]:
R ↔ X + eX ↔ O + e
studied on a rotating disk electrode with DR = DX = DO.
2.3.2 Reduced concentration impedance
Concentration impedances of soluble species:
ZXi(S) =
(1 + α
th√
S√S
)th
√S√
S
1 + βth
√S√
S
, α, β ≷ 0 (2.7)
2.3.3 Nyquist diagrams
Figs. 2.4, 2.5 and 2.6.
Figure 2.4: Some amazing Nyquist diagrams calculated from Eq. (2.7), α = −1,β = −10 (left), β = −104 (right). Red dots : uc1 = 2.54, black dots : uc2 = β2.a: α = −1, β = −10, b: α = −1, β = −10−4, c: α = −2.5, β = −10−5, d: α =−2.5, β = −10 (Hokusai’s great wave).
2.3.
(1 + α TH
√S√
S
)TH
√S√
S
1 + β TH√
S√S
13
Figure 2.5: Array of impedance diagrams calculated from Eq. (2.7). Red dots :uc1 = 2.54, black dots : uc2 = β2.
14 CHAPTER 2. IMPEDANCE CONTAINING TH√
S√S
Figure 2.6: Array of impedance diagrams calculated from Eq. (2.7). Red dots :uc1 = 2.54.
Chapter 3
Impedance containinglumped and distributedelements
3.1
th√
S√S
1 + α S
Z(S) =th
√S√
S
1 + α S(3.1)
Characteristic frequencies:
• uc1 = 2.54
• uc2 = 1/α
3.1.1 Pole-zero map
• Same zeros asth
√S√
S
• Same poles asth
√S√
Splus one real pole (− 1
α) (Figs. 3.4-3.1).
3.1.2 Nyquist diagrams
Figs. 3.4-3.1.
• uc1 ≪ uc2 ⇒ Z(S) ≈ th√
S√S
• uc1 ≫ uc2 ⇒ Z(S) ≈ 11 + α S
15
16 CHAPTER 3. MIXED IMPEDANCE
-
Π2
4-
H3 ΠL2
4-
H5 ΠL2
4-
H7 ΠL2
4
0
-Π2
-H2ΠL2-H3ΠL2-H4ΠL2
Re sIm
s
0.0 0.2 0.4 0.6 0.8 1.00.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Re H
-Im
H
Figure 3.1: Pole-zero map and Nyquist diagram of1
1 + α S
th√
S√S
. α = 10−4.
Red dot: uc1 = 2.54, black dot: uc2 = 1/α.
-
Π2
4-
H3 ΠL2
4-
H5 ΠL2
4-
H7 ΠL2
4
0
-Π2
-H2ΠL2-H3ΠL2-H4ΠL2
Re s
Ims
0.0 0.2 0.4 0.6 0.8 1.00.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Re H
-Im
H
Figure 3.2: Pole-zero map and Nyquist diagram of1
1 + α S
th√
S√S
. α = 10−2.
Red dot: uc1 = 2.54, black dot: uc2 = 1/α.
3.1.
TH√
S√S
1 + α S17
-
Π2
4-
H3 ΠL2
4-
H5 ΠL2
4-
H7 ΠL2
4
0
-Π2
-H2ΠL2-H3ΠL2-H4ΠL2
Re s
Ims
0.0 0.2 0.4 0.6 0.8 1.00.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Re H
-Im
H
Figure 3.3: Pole-zero map and Nyquist diagram of1
1 + α S
th√
S√S
. α = 1
(− 1α
> −π2
4). Red dot: uc1 = 2.54, black dot: uc2 = 1/α.
-
Π2
4-
H3 ΠL2
4-
H5 ΠL2
4-
H7 ΠL2
4
0
-Π2
-H2ΠL2-H3ΠL2-H4ΠL2
Re s
Ims
0.0 0.2 0.4 0.6 0.8 1.00.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Re H
-Im
H
Figure 3.4: Pole-zero map and Nyquist diagram of1
1 + α s
th√
S√S
. α = 103
(− 1α
> −π2
4). Red dot: uc1 = 2.54, black dot: uc2 = 1/α.
18 CHAPTER 3. MIXED IMPEDANCE
Figure 3.5: Change of Nyquist diagram of1
1 + α S
th√
S√S
with increasing value
of α from 10−3 to 100.9. Decimal logarithm of α reported on the Nyquistdiagrams. Red dots: uc1 = 2.54, black dots: uc2 = 1/α.
3.2.1 + α TH
√S√
S
1 + β S19
3.21 + α th
√S√
S
1 + β S
3.2.1 Electrochemical reaction: Volmer-Heyrovsky (V-H)
Electrochemical reaction: Volmer-Heyrovsky (V-H) [4,8]
A+ + s + e− → A,sA+ + A,s + e− → A2 + s
3.2.2 Reduced concentration impedance of adsorbedspecies
Z∗θ (S) =
1 + αth
√S√
S1 + β S
=1
1 + β S+
αth
√S√
S1 + β S
(3.2)
α → ∞ ⇒ Z∗θ (S) ≈ α
th√
S√S
⇒ uc1 = 2.54 (3.3)
α → 0 ⇒ Z∗θ (S) ≈ 1
1 + β iu⇒ uc2 =
1β
(3.4)
3.2.3 Nyquist diagrams
Figs. 3.6 and 3.7.
Figure 3.6: Impedance diagrams calculated from Eq. (3.2)). a : α = 1, β = 10−5,b : α = 103, β = 10−3, c : α = 10−3, β = 10−3, d : α = 103, β = 1. Characteristicdimensionless frequencies: red dots : uc1 = 2.54, black dots : uc2 = 1/β.
20 CHAPTER 3. MIXED IMPEDANCE
Figure 3.7: Array of impedance diagrams calculated from Eq. (3.2). Impedancediagrams are made of one or two arcs. Characteristic dimensionless frequencies: reddots : uc1 = 2.54, black dots : uc2 = 1/β.
3.3.1
1 + α S + β S TH√
S√S
21
3.31
1 + α S + β S th√
S√S
3.3.1 Electrochemical reaction: catalytic copperdeposition
Cu2++Cl− + s + e−→ CuCl,sCuCl,s + e− → Cu + Cl− + s
Hypotheses: no mass transfer limitation for Cu2+, (Cu2+(0, t) ≈ Cu2+), kineticirreversibility of the two steps [18,19].
3.3.2 Reduced concentration impedance of adsorbed species
Z(S) =1
1 + α S + β Sth
√S√
S
(3.5)
• Poles and zeros of Z∗(S) are real and interlaced.
• Zeros of Z(S) are the poles ofth
√S√
S: − 1
4 ((2k + 1) π)2, k = 1 · · ·∞.
• Characteristic dimensionless frequencies: uc1 = 2.54, uc2 = 1/α, uc3 =1/β
3.3.3 Nyquist diagrams
Figs. 3.8 and 3.9.
22 CHAPTER 3. MIXED IMPEDANCE
0
-Π
2
4-I3 ΠM2
4-I5 ΠM2
4-I7 ΠM2
4
Re s
Ims
0 0.5 10
0.5
Re Z
-Im
Z
ZΘ
Figure 3.8: Pole-zero map and impedance diagrams calculated from Eq. (3.5). α =10−2, β = 1, red dot : uc1 = 2.54, black dot: uc2 = 1/α, blue dot: uc3 = 1/β.
3.3.1
1 + α S + β S TH√
S√S
23
Figure 3.9: Graphics array representation of the impedance diagram, calculatedform Eq. (3.5) and plotted using the Nyquist representation (orthonormal scales)for catalytic copper deposition. Characteristic dimensionless frequencies: red dots :uc1 = 2.54, black dots: uc2 = 1/α, blue dots: uc3 = 1/β.
24 CHAPTER 3. MIXED IMPEDANCE
3.4S th
√S√
S
1 + α S + β S th√
S√S
3.4.1 Electrochemical reaction: catalytic copperdeposition
Cu2++Cl− + s + e−→ CuCl,sCuCl,s + e− → Cu + Cl− + s
Hypotheses: no mass transfer limitation for Cu2+, (Cu2+(0, t) ≈ Cu2+), kineticirreversibility of the two steps [19].
3.4.2 Reduced concentration impedance of solublespecies Cl−
Z(S) =S
th√
S√S
1 + α S + β Sth
√S√
S
(3.6)
3.4.3 Nyquist diagrams
• Poles and zeros of Z(S) are real.
• Zeros of Z(S) are the zeros ofth
√S√
S(SZ = −(k π)2, k = 1 · · ·∞) plus
one zero at the origine of the complex plane (derivator).
• Characteristic dimensionless frequencies: uc1 = 2.54, uc2 = 1/α, uc3 =1/β, uc4 = (β/α)2.
Fig. 3.10.
3.4.S TH
√S√
S
1 + α S + β S TH√
S√S
25
Figure 3.10: Graphics array representation of the reduced impedance diagram cal-culated from Eq. (3.6) and plotted using the Nyquist complex plane representation(orthonormal scales) for catalytic copper deposition. Characteristic dimensionless fre-quencies: red dots : uc1 = 2.54, black dots: uc2 = 1/α, blue dots: uc3 = 1/β, greendots: uc4 = (β/α)2.
26 CHAPTER 3. MIXED IMPEDANCE
3.51 + α th
√S√
S
1 + β S + γ S th√
S√S
3.5.1 Electrochemical reaction: E-EAR reaction [20]
R + s → O + s + n1 eA− + s ↔ A,s + n2 e−
3.5.2 Reduced concentration impedance of adsorbed species
Z(S) =1 + α
th√
S√S
1 + β S + γ Sth
√S√
S
, α, β, γ ≷ 0 (3.7)
3.5.3 Nyquist diagrams
Figure 3.11: Graphics array representation of the Nyquist diagram for the impedancecalculated from Eq. (3.7) and plotted using the Nyquist representation (orthonormalscales). Characteristic dimensionless angular frequencies: red dots: uc1 = 2.54, blackdots: uc2 = 1/β1. γ = 10−2.
3.5.1 + α TH
√S√
S
1 + β S + γ S TH√
S√S
27
Figure 3.12: Graphics array representation of the Nyquist diagram for the impedancecalculated from Eq. (3.7) and plotted using the Nyquist representation (orthonormalscales). Characteristic dimensionless angular frequencies: red dots: uc1 = 2.54, blackdots: uc2 = 1/β1. γ = −10−1.
28 CHAPTER 3. MIXED IMPEDANCE
Figure 3.13: Graphics array representation of the Nyquist diagram for the impedancecalculated from Eq. 3.7 and plotted using the Nyquist representation (orthonormalscales). α, β, γ < 0. Characteristic dimensionless angular frequencies: red dots:uc1 = 2.54, black dots: uc2 = 1/|β1|. α, β, γ < 0, γ = −10−1.
3.6.(1 + α S) TH
√S√
S
1 + β S + γ S TH√
S√S
29
3.6(1 + α S) th
√S√
S
1 + β S + γ S th√
S√S
3.6.1 Electrochemical reaction: E-EAR reaction [20]
R + s → O + s + n1 eA− + s → A,s + n2 e−
3.6.2 Reduced concentration impedance of solublespecies R
Z(S) =(1 + α S)
th√
S√S
1 + β S + γ Sth
√S√
S
, α, β, γ ≷ 0 (3.8)
3.6.3 Nyquist diagrams
Figs. 3.14 and 3.15.
30 CHAPTER 3. MIXED IMPEDANCE
Figure 3.14: Graphics array representation of the Nyquist diagram for the impedancecalculated from Eq. (3.8) and plotted using the Nyquist representation (orthonormalscales). Characteristic dimensionless angular frequencies: red dots: uc1 = 2.54, blackdots: uc2 = 1/β. γ = 10−3.
3.6.(1 + α S) TH
√S√
S
1 + β S + γ S TH√
S√S
31
Figure 3.15: Graphics array representation of the Nyquist diagram for the impedancecalculated from Eq. (3.8) and plotted using the Nyquist representation (orthonormalscales). α, β, γ < 0. Characteristic dimensionless angular frequencies: red dots:uc1 = 2.54, black dots: uc2 = 1/|β|. γ = 10−3.
Appendix A
Some rational fractions in√S
A.1 Introduction
The use of a rational fraction in√
S
Z(√
S) =∑N
m=0 bm(√
S)m∑Pp=0 ap(
√S)p
(A.1)
has been proposed by Pintelon et al. [21, 22]. Some rational fraction in√
S arestudied below.
A.21
1 +√
S
H(u) =1
1 +√
iu(A.2)
Re H(u) =√
2√
u + 22(u +
√2√
u + 1) , Im H(u) = −
√u√
2(u +
√2√
u + 1) (A.3)
|H(u) − (1/2 + i/2)| =√
(Re H(u) − 1/2)2 + (Im H(u) − 1/2)2 =√
22
⇒ circle, radius =√
22
(A.4)
Nyquist diagram: Fig. A.1.
A.31
1 + (√
S)3
H(u) =1
1 + (iu)(3/2)(A.5)
33
34 APPENDIX A. SOME RATIONAL FRACTIONS IN√
S
Figure A.1: Nyquist diagram of1
1 +√
iu. One quarter circle. uc = 1,
Im H(uc) = − 1√2(2 +
√2) .
Re H(u) =√
2u3/2 − 22(√
2u3/2 − u3 − 1) , Im H(u) = − u3/2
−2u3/2 +√
2u3 +√
2(A.6)
|H(u) − (1/2 − i/2)| =√
(Re H(u) − 1/2)2 + (Im H(u) − 1/2)2 =√
22
⇒ circle, radius =√
22
(A.7)
Remarkable frequencies
u1 =3√
3 − 2√
2, u2 = 1, u3 = 3√
2, u4 =3√
3 + 2√
2 (A.8)
Nyquist diagram: Fig. A.2.
Figure A.2: Nyquist diagram of1
1 + (iu)3/2. Three quarter circle.
A.4.1 + (
√S)2√
S (1 + α(√
S)2)35
A.41 + (
√S)2
√S (1 + α(
√S)2)
H(u) =1 + (
√iu)2√
iu (1 + α (√
iu)2)(A.9)
Re H(u) =u(α(u − 1) + 1) + 1√
2√
u (α2u2 + 1), Im H(u) =
−u(αu + α − 1) − 1√2√
u (α2u2 + 1)(A.10)
Three different limiting cases
• α ≪ 1, Nyquist and Bode diagrams: Fig. A.3
u1 = uIm H=0 =−√
α2 − 6α + 1 − α + 12α
≈ 1 (A.11)
u2 = uIm H=0 =+√
α2 − 6α + 1 − α + 12α
≈ 1α
(A.12)
• α = 1, H(u) =1√iu
• α ≫ 1, Nyquist diagram: Fig. A.4
u1 = uReH=0 =−√
α2 − 6α + 1 + α − 12α
≈ 1α
(A.13)
u2 = uReH=0 =√
α2 − 6α + 1 + α − 12α
≈ 1 (A.14)
A.51 − (
√S)2
√S (1 − α(
√S)2)
H(u) =1 − (
√iu)2√
iu (1 − α (√
iu)2)(A.15)
Re H(u) =u(α + αu − 1) + 1√
2√
u (α2u2 + 1), Im H(u) =
u(α + α(−u) − 1) − 1√2√
u (α2u2 + 1)(A.16)
Three different limiting cases
• α ≪ 1, Nyquist diagram: Fig. A.5
u1 = uRe H=0 =−√
α2 − 6α + 1 − α + 12α
≈ 1 (A.17)
u2 = uRe H=0 =√
α2 − 6α + 1 − α + 12α
≈ 1α
(A.18)
• α = 1, H(u) =1√iu
• α ≫ 1.
36 APPENDIX A. SOME RATIONAL FRACTIONS IN√
S
Figure A.3: Nyquist and Bode (modulus) diagram of1 + (
√iu)2√
iu (1 + α (√
iu)2).
a ≪ 1. Red dot: u2 =≈ 1/α, black dot: u1 = 0 ≈ 1.
Figure A.4: Nyquist and Bode (modulus) diagram of1 + (
√iu)2√
iu (1 + α (√
iu)2).
a ≫ 1. Red dot: uIm H=0 ≈ 1/α, black dot: uIm H=0 ≈ 1.
A.5.1 − (
√S)2√
S (1 − α(√
S)2)37
Figure A.5: Nyquist and Bode (modulus) diagram of1 − (
√iu)2√
iu (1 − α (√
iu)2).
a ≪ 1. Red dot: u2 =≈ 1/α, black dot: u1 = 0 ≈ 1.
Appendix B
Impedance structure ofreactions involving bothadsorbed and solublespecies
Table B.1: Impedance structure of reactions involving both adsorbed and solublespecies. First order denominator.
Expression Reaction Impedance
1 + αth
√S√
S1 + β S
(V-H)A+ + s + e− → A,s
A+ + A,s + e− → A2 + s Zθ
Table B.2: Impedance structure of reactions involving both adsorbed and solublespecies. Second order denominator.
Expression Reaction Impedance
1 + α s + βth
√S√
S+ γ s
th√
S√S
1 + δ S + ϵ S2
(V-H) with desorptionA+ + s + e− → A,s
A+ + A,s + e− → A2,sA2,s → A2 + s
Zθ
39
40APPENDIX B. REACTIONS INVOLVING ADSORBED AND SOLUBLE SPECIES
Table B.3: Impedance structure of reactions involving both adsorbed and soluble
species. Denominateur : 1 + α S + βth
√S√
SExpressions Reactions Impedances
1
1 + α S + βth
√S√
S
(catalytic)A2+ + B− + s + e− → AB,sAB,s + e− → A + B− + s
Hyp. A2+(0, t) = cteZθ
th√
S√S
1 + β s + γ Sth
√S√
S
(catalytic)A2+ + B− + s + e− → AB,sAB,s + e− → A + B− + s
Hyp. A2+(0, t) = cteZB−
Table B.4: Impedance structure of reactions involving both adsorbed and soluble
species. Denominateur : 1 + β S + γ Sth
√S√
S.
Expressions Reactions Impedances
1 + α S
1 + β S + γ Sth
√S√
S
(V-H)#2A+ + s + e− → A,sA,s + e− → A− + s Zθ
1 + αth
√S√
S
1 + β S + γ Sth
√S√
S
(E-EAR)R + s → O + s + n1 eA− + s ↔ A,s + n2 e− Zθ
(1 + α S)th
√S√
S
1 + β S + γ Sth
√S√
S
(E-EAR)R + s → O + s + n1 eA− + s ↔ A,s + n2 e− ZR
(V-H)#2A+ + s + e− → A,sA,s + e− → A− + s ZA+
Table B.5: Impedance structure of reactions involving both adsorbed and soluble
species. Denominateur : 1 + β s + γth
√S√
S+ δ S
th√
S√S
.
Expression Reaction Impedance
1 + αth
√S√
s
1 + β S + γth
√S√
S+ δ s
th√
S√s
(DP3)M,s → M2+ + s + 2 e−
M,s + A2− → MA,s + 2 e−
MA,s + B → MAB + sHyp. A2−(0, t) = A2−∗
Zs
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