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Transcript of Handbook of electrochemical impedance spectroscopy.pdf
Handbookof
Electrochemical Impedance Spectroscopy
-0.2 Ecorr 0.2
-1
0
1
EV
i fÈi d
OÈ
ififMifO
0 Rct Rp
0
0.4
Re Z
-Im
Z
Ω = 1HRctCdlL
Ω = Α2Τ
CORROSIONREACTIONS LIBRARY
J.-P. Diard, C. Montella, N. MurerLEPMI, Bio-Logic
Hosted by Bio-Logic @ www.bio-logic.info
July 17, 2012
2
Contents
1 Reactions without adsorbed species 51.1 Reactions without mass transport limitation . . . . . . . . . . . . 5
1.1.1 Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . 51.1.2 Kinetic equations . . . . . . . . . . . . . . . . . . . . . . . 51.1.3 Steady-state conditions . . . . . . . . . . . . . . . . . . . 51.1.4 Faradaic impedance . . . . . . . . . . . . . . . . . . . . . 6
1.2 Reactions with mass transport limitation . . . . . . . . . . . . . 81.2.1 Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . 81.2.2 Example: Iron in aerobic solution [4] . . . . . . . . . . . . 81.2.3 Kinetic equations . . . . . . . . . . . . . . . . . . . . . . . 81.2.4 Steady-state conditions . . . . . . . . . . . . . . . . . . . 81.2.5 Faradaic impedance [3] . . . . . . . . . . . . . . . . . . . . 9
2 Reactions involving one adsorbate 112.1 Volmer-Heyrovsky (V-H) corrosion reaction . . . . . . . . . . . . 11
2.1.1 Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . 112.1.2 Kinetic equations . . . . . . . . . . . . . . . . . . . . . . . 112.1.3 Steady-state conditions . . . . . . . . . . . . . . . . . . . 122.1.4 Faradaic impedance . . . . . . . . . . . . . . . . . . . . . 13
2.2 (V-H) corrosion reaction with mass transport limitation . . . . . 152.2.1 Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . 152.2.2 Kinetic equations . . . . . . . . . . . . . . . . . . . . . . . 152.2.3 Steady-state conditions . . . . . . . . . . . . . . . . . . . 152.2.4 Faradaic impedance . . . . . . . . . . . . . . . . . . . . . 16
2.3 Volmer-Tafel (V-T) corrosion reaction . . . . . . . . . . . . . . . 192.3.1 Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . 192.3.2 Kinetic equations . . . . . . . . . . . . . . . . . . . . . . . 192.3.3 Steady-state conditions . . . . . . . . . . . . . . . . . . . 192.3.4 Faradaic impedance . . . . . . . . . . . . . . . . . . . . . 20
3
4 CONTENTS
Chapter 1
Electrochemical reactionswithout adsorbed species
1.1 Electrochemical reactions without mass trans-port limitation
1.1.1 Mechanism
M Ko1−→ Mn1+ + n1 e−
O + n2 e Kr2−→ R
1.1.2 Kinetic equations
Butler-Volmer kinetic, kinetic irreversibility of electrochemical reactions (kr1 =ko2 = 0), no mass transport limitation (O(0, t) = O∗).
Ko1 = ko1 exp (αo1 n1 f E) , Kr2 = kr2 exp (−αr2 n2 f E) , f = F/(R T )
Current density vs. step rates
if(t) = F (n1 v1(t) − n2 v2(t))
Step rates
v1(t) = Ko1(t), v2(t) = Kr2(t) O∗
1.1.3 Steady-state conditions
Step rates
v1 = Ko1, v2 = Kr2 O∗
Current density
if = F (n1 Ko1 − n2Kr2 O∗) (1.1)
5
6 CHAPTER 1. REACTIONS WITHOUT ADSORBED SPECIES
1.1.4 Faradaic impedance
Faradaic impedance
Zf(s) = Rct (1.2)
Charge transfer resistance
Rct =1
f F (n22 O∗ Kr2 αr2 + n2
1 Ko1 αo1)(1.3)
Polarization resistance
Rp = Rct
Relation between Rct, Rp and icorr
Rct(Ecorr) = Rp(Ecorr) =1
f F (n22 O∗ Kr2(Ecorr)αr2 + n2
1 Ko1(Ecorr) αo1)
⇒ icorr =1
f (αo1 n1 + αr2 n2) Rct(Ecorr)
Stern-Geary relationship [5].
Electrode impedance
Z(s) =Zf(s)
1 + sCdl Zf(s)=
Rct
1 + sCdl Rct(1.4)
Ecorr
icorr
- icorr
E
i f
ififMifO
0 Rp = Rct
0
Re Z
-Im
Z
Ωc=1HRctCdlL
Figure 1.1: Typical if vs. E curve calculated with Eq. (1.1) and Nyquist impedancediagram calculated at the corrosion potential with Eqs. (1.3)-(1.4).
1.1. REACTIONS WITHOUT MASS TRANSPORT LIMITATION 7
Equivalent circuit
Rct
Cdl
Figure 1.2: Equivalent circuit of the electrode impedance (Eq. (1.4)).
8 CHAPTER 1. REACTIONS WITHOUT ADSORBED SPECIES
1.2 Electrochemical reactions with mass trans-port limitation
1.2.1 Mechanism
M Ko1−→ Mn1+ + n1 e−
O + n2 e Kr2−→ R
1.2.2 Example: Iron in aerobic solution [4]
Fe → Fe2+ + 2e−
O2 +2H2O + 4e− → 4OH−
1.2.3 Kinetic equations
Butler-Volmer kinetic, kinetic irreversibility of electrochemical reactions (kr1 =ko2 = 0), mass transport limitation.
Ko1 = ko1 exp (αo1 n1 f E) , Kr2 = kr2 exp (−αr2 n2 f E) , f = F/(R T )
Mass balance equations
Flux of soluble speciesJO(0, t) = −v2(t)
Current density vs. step rates
if(t) = F (n1 v1(t) − n2 v2(t))
Step rates
v1(t) = Ko1(t), v2(t) = Kr2(t)O(0, t)
1.2.4 Steady-state conditions
Steady-state equations
Soluble speciesJO(0) = −mO (O∗ − O(0))
mO = DO/δO, δO = 1, 611 D1/3O ν1/6 Ω−1/2, mO = 0, 620D
2/3O ν−1/6 Ω1/2
Steady-state solutions
Soluble species
O(0) =O∗mO
Kr2 + mO
Current density
if = F
(n1 Ko1 −
n2 O∗ Kr2 mO
Kr2 + mO
)(1.5)
1.2. REACTIONS WITH MASS TRANSPORT LIMITATION 9
if = ifM + ifO, ifM = n1 F Ko1, ifO = −n2 F O∗ Kr2 mO
Kr2 + mO
idO = limE→−∞
if = −n2 F O∗ mO
1.2.5 Faradaic impedance [3]
Faradaic impedance
Zf(s) = Rct + ZO(s) (1.6)
Charge transfer resistance
Rct =1
f F (n22 O(0)Kr2 αr2 + n2
1 Ko1 αo1)(1.7)
Concentration impedance
Soluble species
ZO(s) =Rct n2
2O(0)MO(s)K2r2αr2
n22O(0)Kr2αr2 + n2
1Ko1αo1 (MO(s)Kr2 + 1)(1.8)
MO(s) =1
mO
th√
τdOs√
τdOs, τdO =
δO
DO
ZO(s) = kO
th√
τdOs√
τdOs
1 + αth
√τdOs
√τdOs
,
α =αo1 n2
1 Ko1 Kr2
mO (αo1 n21 Ko1 + O(0)αr2 n2
2 Kr2), kO =
Rct n22O(0)K2
r2αr2
mO (αo1n21Ko1 + αr2n2
2Kr2O(0))
RO(s) = lims→0
ZO(s) =kO
1 + α
Polarization resistance
Rp = Rct
(1 +
n22O(0)K2
r2αr2
n22O(0)Kr2mOαr2 + n2
1Ko1αo1 (Kr2 + mO)
)Relation between Rct, Rp and icorr
Rct(Ecorr) =1
f F (n22 O(0, Ecorr) Kr2(Ecorr)αr2 + n2
1 Ko1(Ecorr)αo1)
⇒ icorr =1
f (αo1 n1 + αr2 n2) Rct(Ecorr)
icorr =1
f
(αo1 n1 + αr2 n2
(mO
mO + Kr2(Ecorr)
))Rp(Ecorr)
Limiting case
ko1 → ∞ ⇒ Ecorr → −∞ ⇒ icorr ≈1
f αo1 n1 Rp(Ecorr)= −idO
10 CHAPTER 1. REACTIONS WITHOUT ADSORBED SPECIES
Electrode impedance
Z(s) =Zf(s)
1 + sCdl Zf(s)(1.9)
Equivalent circuit
Rct ZO
Cdl
∆O
Rct
R'O
Cdl
Figure 1.3: Equivalent circuits of the electrode impedance (Eq. (1.9)). ZWδO=
R′dO
th√
τdOs√
τdOs, R′
dO = kO, R′O = kO/α.
-0.2 Ecorr 0.2
-1
0
1
EV
i fÈi d
OÈ
ififMifO
0 Rct Rp
0
0.5
Re Z
-Im
Z
Ω = 1HRctCdlL
Ω = 2.54Τ
-0.2 Ecorr 0.2
-1
0
1
EV
i fÈi d
OÈ
ififMifO
0 Rct Rp
0
0.4
Re Z
-Im
Z
Ω = 1HRctCdlL
Ω = Α2Τ
Figure 1.4: Typical if vs. E curve calculated with Eq. (1.5) and Nyquist impedancediagrams calculated at the corrosion potential with Eqs. (1.6)-(1.8) [2, 1].
Chapter 2
Electrochemical reactionsinvolving one adsorbate
2.1 Volmer-Heyrovsky (V-H) corrosion reaction
2.1.1 Mechanism
H+ + s + e− Kr1−→ H,s
H+ + H,s + e− Kr2−→ H2 + s
M,s Ko3−→ M2+ + s + 2 e−
2.1.2 Kinetic equations
No mass transport limitations, Langmuir isotherm
H+(0, t) ≈ H+∗, M, s ≡ s
Kr1 = kr1 exp (−αr1 f E) , kr1 = k′r1 H+∗
Kr2 = kr2 exp (−αr2 f E) , kr2 = k′r2 H+∗, Ko3 = ko3 exp (2 αo3 f E)
Transformation rates
vs(t) = −v1(t) + v2(t), vH(t) = v1(t) − v2(t)
Mass balance equations
Rate of production of adsorbed species
dθs(t)dt
=vs(t)
Γ,dθH(t)
dt=
vH(t)Γ
Current density vs. step rates
if(t) = −F (v1(t) + v2(t) − 2 v3(t))
11
12 CHAPTER 2. REACTIONS INVOLVING ONE ADSORBATE
Step rates
v1(t) = Kr1(t) Γ θs(t), v2(t) = Kr2(t) Γ θH(t), v3(t) = Ko3(t) Γ θs(t)
2.1.3 Steady-state conditions
Steady-state equations
Adsorbed speciesdθs/dt = 0, θH + θs = 1
Steady-state solutions
Adsorbed species
θs =Kr2
Kr1 + Kr2, θH =
Kr1
Kr1 + Kr2
Current density
if =2F Γ (Ko3 Kr2 − Kr1 Kr2)
Kr1 + Kr2(2.1)
if = 0 ⇒ E = Ecorr =1
(αr1 + 2 αo3) fln
(kr1
ko3
)
icorr =2F Γ Ko3(Ecorr)Kr2(Ecorr)
Kr1(Ecorr) + Kr2(Ecorr)=
2 F ΓKr1(Ecorr) Kr2(Ecorr)Kr1(Ecorr) + Kr2(Ecorr)
=2F Γ kr1 kr2
kr1
(kr1
ko3
) αr2
2αo3 + αr1 + kr2
(kr1
ko3
) αr1
2αo3 + αr1
-0.4 -0.2 Ecorr
-0.02
0
0.02
EV
i fHA
cm-
2L
Figure 2.1: if vs. E curve calculated with Eq. (2.1) for kr1 = 1 s−1, kr2 = 1 s−1,ko3 = 101 s−1, αr1 = 0.8, αr2 = 0.3, αo3 = 0.4, Γ = 10−9 mol cm−2, f = 38.9 V−1,F = 96485 C mol−1.
2.1. VOLMER-HEYROVSKY (V-H) CORROSION REACTION 13
2.1.4 Faradaic impedance
Faradaic impedance
Zf(s) = Rct + ZH(s) + Zs(s)
Zf(s) =(Kr2 + Kr1)(Kr2 + Kr1 + s)
fFΓKr2(αr1Kr1(2(Ko3 + Kr2) + s) + 4αo3Ko3(Kr2 + Kr1 + s) + αr2Kr1(−2Ko3 + 2Kr1 + s))
Charge transfer resistance
Rct =1
f F Γ (αr2 θH Kr2 + (4 αo3 Ko3 + αr1 Kr1) θs)=
Kr2 + Kr1
f F Γ Kr2 (4αo3 Ko3 + (αr1 + αr2)Kr1)
Polarization resistance
Rp =(Kr2 + Kr1)2
2 f F Γ Kr2 (2 αo3 Ko3(Kr2 + Kr1) + Kr1 (αr1 (Ko3 + Kr2) + αr2(Kr1 − Ko3)))
No simple relation between Rp and icorr.
Relation between Rct and icorr
Rct(Ecorr) =1
f F Γ (αr2 θH(Ecorr)Kr2(Ecorr) + (4 αo3 Ko3(Ecorr) + αr1 Kr1(Ecorr)) θs(Ecorr))
⇒ icorr =1
(2αo3 + (αr1 + αr2)/2) f Rct(Ecorr)
14 CHAPTER 2. REACTIONS INVOLVING ONE ADSORBATE
0 0.5 1 RctRp
0
0.5
Re Z Rp
-Im
ZR
p
E = Ecorr
Zf
Z
0 0.5 1RctRp
0
0.5
Re Z Rp
-Im
ZR
p
EV = Ecorr-0.04Zf
Z
-2 0 2 4
-1
0
logHΩHradsLL
logÈ
ZR
pÈ
E = Ecorr
Zf
Z
0 5
-0.2
0
logHΩHradsLL
logÈ
ZR
pÈ
EV = Ecorr-0.04Zf
Z
Figure 2.2: Two typical Nyquist impedance and Bode diagrams for the Volmer-Heyrovsky (V-H) corrosion reaction (Thick lines: Faradaic impedance, thin lines:electrode impedance). Parameters value as in Fig. 2.1 and Cdl = 10−5 F.
2.2. (V-H) CORROSION REACTION WITH MASS TRANSPORT LIMITATION15
2.2 Volmer-Heyrovsky (V-H) corrosion reactionwith mass transport limitation
2.2.1 Mechanism
H+ + s + e− Kr1−→ H,s
H+ + H,s + e− Kr2−→ H2 + s
M,s Ko3−→ M2+ + s + 2 e−
2.2.2 Kinetic equations
Butler-Volmer kinetic, Langmuir isotherm, with mass transfer limitation,M, s ≡ s.
Kr1 = kr1 exp (−αr1 f E) , Kr2 = kr2 exp (−αr2 f E) ,
Ko3 = ko3 exp(αo3 2 f E), f = F/(R T )
Mass balance equations
Flux of soluble species
JH+(0, t) = −v1(t) − v2(t)
Rate of production of adsorbed species
dθs(t)dt
=−v1(t) + v2(t)
Γ,dθH(t)
dt=
v1(t) − v2(t)Γ
Current density vs. step rates
if(t) = −F (v1(t) + v2(t) − 2 v3(t))
Step rates
v1(t) = Kr1(t)H+(0, t) Γ θs(t), v2(t) = Kr2(t)H+(0, t) Γ θH(t), v3(t) = Ko3(t) Γ θs(t)
2.2.3 Steady-state conditions
Steady-state equations
Soluble speciesJH+(0) = −mH+(H+∗ − H+(0))
mH+ = DH+/δH+ , δH+ = 1, 611D1/3
H+ ν1/6 Ω−1/2, mH+ = 0, 620 D2/3
H+ ν−1/6 Ω1/2
Adsorbed speciesdθs/dt = 0, θH + θs = 1
16 CHAPTER 2. REACTIONS INVOLVING ONE ADSORBATE
Steady-state solutions
Soluble species
H+(0) =H+* (Kr1 + Kr2) mH+
2ΓKr1Kr2 + (Kr1 + Kr2)mH+,
Adsorbed species
θs =Kr2
Kr1 + Kr2, θH =
Kr1
Kr1 + Kr2
Current density
if =2FΓKr2
(mH+ (Kr1 + Kr2)
(Ko3 − H+*Kr1
)+ 2ΓKo3Kr1Kr2
)(Kr1 + Kr2) (mH+ (Kr1 + Kr2) + 2ΓKr1Kr2)
(2.2)
0 0.1 0.2 0.3-0.04
0
0.04
EV
i fHA
cm-
2L
Figure 2.3: if vs. E curve calculated with Eq. (2.2) for kr1 = 107 mol−1 cm3 s−1,kr2 = 107 mol−1 cm3 s−1, ko3 = 10−2 s−1, αr1 = 0.8, αr2 = 0.3, αo3 = 0.5, DH+ = 10−6
cm2 s−1, ν = 10−2 cm2 s−1, Ω = 100 rpm, Γ = 10−9 mol cm−2, f = 38.9 V−1,F = 96485 C mol−1.
2.2.4 Faradaic impedance
Faradaic impedance
Zf(s) = Rct + ZH+(s) + Zθ(s), Zθ(s) = Zs(s) + ZH+(s)
Zf(s) =af1 + saf2 + af3MH+(s) + saf4MH+(s)bf1 + sbf2 + bf3MH+(s) + sbf4MH+(s)
af1 = (Kr1 + Kr2) H+(0), af2 = 1, af3 = 2ΓKr1Kr2H+(0), af4 = Γ (Kr2θH + Kr1θs )
bf1 = 2fFΓH+(0)(θH Kr2αr2
(Kr1H
+(0) − Ko3
)+ θs
(Kr1αr1
(Kr2H
+(0) + Ko3
)+ 2Ko3αo3 (Kr1 + Kr2)
))bf2 = fFΓ
(θH Kr2αr2H
+(0) + Kr1αr1θs H+(0) + 4Ko3αo3θs
)bf3 = 4fFΓ2Ko3Kr1Kr2θs H+(0) (θH (αr1 − αr2) + 2αo3) , bf4 = 4fFΓ2Ko3αo3θs (θH Kr2 + Kr1θs )
2.2. (V-H) CORROSION REACTION WITH MASS TRANSPORT LIMITATION17
Charge transfer resistance
Rct =1
fFΓ (θH Kr2αr2H+(0) + Kr1αr1θs H+(0) + 4Ko3αo3θs )
Polarization resistance
Rp = (mH+ (Kr1 + Kr2) + 2ΓKr1Kr2) /(2fFΓ
(mH+
(θH Kr2αr2
(Kr1H
+(0) − Ko3
)+ θs
(Kr1αr1
(Kr2H
+(0) + Ko3
)+2Ko3αo3 (Kr1 + Kr2))) + 2ΓKo3Kr1Kr2θs (θH (αr1 − αr2) + 2αo3)))
No simple relation between Rp and icorr.
Relation between Rct and icorr
Rct(Ecorr) =1
fFΓ (θH (Ecorr)Kr2(Ecorr)αr2H+(0, Ecorr) + Kr1(Ecorr)αr1θs (Ecorr)H+(0, Ecorr) + 4Ko3(Ecorr)αo3θs (Ecorr))
⇒ icorr =1
(2αo3 + (αr1 + αr2)/2) f Rct(Ecorr)
18 CHAPTER 2. REACTIONS INVOLVING ONE ADSORBATE
0 0.5 1
0
0.5
Re Z Rp
-Im
ZR
p
E = Ecorr
Zf
Z
0 0.5 1
0
0.5
Re Z Rp
-Im
ZR
p
EV = Ecorr-0.06Zf
Z
0 5
-0.2
0
logHΩHradsLL
logÈ
ZR
pÈ
E = Ecorr
Zf
Z
0 5
-0.2
0
logHΩHradsLL
logÈ
ZR
pÈ
EV = Ecorr-0.06Zf
Z
Figure 2.4: Two typical Nyquist impedance and Bode diagrams for the Volmer-Heyrovsky (V-H) corrosion reaction with mass transport limitation (Thick lines:Faradaic impedance, thin lines: electrode impedance). Parameters value as in Fig. 2.3and Cdl = 5 × 10−5 F.
2.3. VOLMER-TAFEL (V-T) CORROSION REACTION 19
2.3 Volmer-Tafel (V-T) corrosion reaction
2.3.1 Mechanism
H+ + s + e− Kr1−→ H,s
2 H,s kd2−→ H2 + 2 s
M,s Ko3−→ M2+ + s + 2 e−
2.3.2 Kinetic equations
No mass transport limitations, Langmuir isotherm, H+(0, t) ≈ H+∗, M, s ≡ s,Kr1 = kr1 exp (−αr1 f E) , kr1 = k′
r1 H+∗ Ko3 = ko3 exp (2αo3 f E) , ko1 =0, kr3 = 0.
Mass balance equations
Rate of production of adsorbed species
dθs(t)dt
=−v1(t) + 2 v2(t)
Γ,dθH(t)
dt=
v1(t) − 2 v2(t)Γ
Current density vs. step rates
if(t) = −F (v1(t) − 2 v3(t))
Step rates
v1(t) = Kr1(t) Γ θs(t), v2(t) = kd2 (Γ θH(t))2, v3(t) = Ko3(t) Γ θs(t)
2.3.3 Steady-state conditions
Steady-state equations
Adsorbed speciesdθs/dt = 0, θH + θs = 1
Steady-state solutions
Adsorbed species
θs =4Γkd2 + Kr1 −
√Kr1
√8Γkd2 + Kr1
4Γkd2, θs + θH = 1
Current density
if =4FΓ2kd2 (2Ko3 − Kr1)
4Γkd2 + Kr1 +√
Kr1
√8Γkd2 + Kr1
(2.3)
if = 0 ⇒ E = Ecorr =1
f (2αo3 + αr1)log
(kr1
2ko3
)
20 CHAPTER 2. REACTIONS INVOLVING ONE ADSORBATE
icorr =23−exp2FΓ2kd2ko3
(ko3kr1
)− exp2
2exp1kr1
(ko3kr1
)exp1 + 4Γkd2 +
√2exp1
(ko3kr1
)exp1kr1
√2exp1kr1
(ko3kr1
)exp1 + 8Γkd2
withexp1 =
αr1
2αo3 + αr1, exp2 =
2αo3
2αo3 + αr1
-0.4 -0.2 Ecorr
0
0.05
EV
i fHm
Acm-
2L
Figure 2.5: if vs. E curve calculated with Eq. (2.3) for kr1H+∗ = 10−3 s−1, kd2 = 108
mol−1 cm2 s−1, ko3 = 10−1 s−1, αr1 = 0.7, αo3 = 0.4, n3 = 1, Γ = 10−9 mol cm−2,f = 38.9 V−1, F = 96485 C mol−1.
2.3.4 Faradaic impedance
Transfer resistance
Rct =1
fFΓ (4Ko3αo3 + Kr1αr1) θs
Concentration impedance
Zs(s) =Kr1 (Kr1 − 2Ko3)Rctαr1
2Ko3Kr1αr1 + Kr1 (s + 4Γkd2θH) αr1 + 4Ko3αo3 (s + Kr1 + 4Γkd2θH)
Faradaic impedance
Zf(s) = Rct + Zs(s)
Zf(s) = Rct
(1 +
Kr1 (Kr1 − 2Ko3)αr1
2Ko3Kr1αr1 + Kr1 (s + 4Γkd2θH) αr1 + 4Ko3αo3 (s + Kr1 + 4Γkd2θH)
)Polarization resistance
Rp = Rct
(1 +
Kr1 (Kr1 − 2Ko3)Rctαr1
2Ko3Kr1 (2αo3 + αr1) + 4Γkd2 (4Ko3αo3 + Kr1αr1) θH
)No simple relation between Rp(Ecorr) and icorr.
Relation between Rct(Ecorr) and icorr
icorr =1
f (2αo3 + αr1) Rct(Ecorr)
2.3. VOLMER-TAFEL (V-T) CORROSION REACTION 21
Equivalent circuit
Zs =Rs
1 + Rs Cs s, Cs =
4Ko3αo3 + Kr1αr1
Kr1 (Kr1 − 2Ko3) Rctαr1
Rs =Kr1 (Kr1 − 2Ko3)Rctαr1
2Ko3Kr1 (2αo3 + αr1) + 4Γkd2 (4Ko3αo3 + Kr1αr1) θA
0 0.5 1
0
0.45
Re Z Rp
-Im
ZR
p
E = Ecorr
Zf
Z
0 0.5 1
0
0.45
Re Z Rp
-Im
ZR
p
EV = Ecorr+0.04
Zf
Z
-2 0 2
-1
0
logHΩHradsLL
logÈ
ZR
pÈ
E = Ecorr
Zf
Z
-2 0 2
-0.5
0
logHΩHradsLL
logÈ
ZR
pÈ
EV = Ecorr+0.04
Zf
Z
Figure 2.6: Two typical Nyquist impedance and Bode diagrams for the Volmer-Tafel (V-T) corrosion reaction (Thick lines: Faradaic impedance, thin lines: electrodeimpedance). Parameters value as in Fig. 2.5 and Cdl = 1 × 10−5 F.
22 CHAPTER 2. REACTIONS INVOLVING ONE ADSORBATE
Rct
Cdl
Cs
Rs
Figure 2.7: Equivalent circuit for the impedance of (V-T) corrosion reaction.
Bibliography
[1] Diard, J.-P., B. Le Gorrec, and Montella, C. Hand-book of electrochemical impedance spectroscopy. Diffusion Impedances.www.bio-logic.info/potentiostat/notes.html (2012).
[2] Macdonald, J. R. Impedance spectroscopy: old problems and new devel-opments. Electrochim. Acta 35 (1990), 1483–1492.
[3] Montella, C., Diard, J.-P., and B. Le Gorrec. Exercices de cinetiqueelectrochimique. II. Methode d’impedance. Hermann, Paris, 2005.
[4] Orazem, M. E., and Tribollet, B. Electrochemical impedance spec-troscopy. John Wiley & Sons, Hoboken, 2008.
[5] Stern, M., and Geary, A. J. Electrochemical polarization. I. A theo-retical analysis of the shape of polarization curves. J. Electrochem. Soc 104(1957), 56–63.
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