Deck 6: Eis Other Physical Phenomena

Question 1

For a simple electron transfer reaction, the coupling of mass transfer and kinetics at the electrode surface is described by

A) relating the species flux and the current
B) equating the species concentration with the bulk concentration
C) Fick's second law
D) none of the above

Answer 1

A

Question 2

In case of a rotating disc electrode (RDE), as per Levich equation, the diffusion layer thickness depends on kinematic viscosity ( $\nu$ ) as

A) $$v ^ { 1 / 2 }$$
B) $$v ^ { 1 / 3 }$$
C) $$v ^ { 1 / 6 }$$
D) $$v ^ { 2 }$$

Answer 2

$$v ^ { 1 / 6 }$$

Question 3

In the derivation of the Warburg impedance equation, it is assumed that the following effects can be neglected

A) diffusion
B) convection
C) electromigration
D) none of the above

Answer 3

B,C

Question 4

Consider the following reaction $$A \underset { k _ { 2 } } { \stackrel { k _ { 1} } { \rightleftarrows } }B + e ^ { - }$$


. The concentration of A and B in bulk solution are equal. When a positive dc bias is applied (vs. OCP), under steady-state conditions, on the surface,

A) C_A > C_B
B) C_A < C_B
C) C_A = C_B
D) it could be any of the above depending on kinetic parameter values.

Question 5

For a simple electron transfer reaction, with finite diffusion layer thickness (bounded Warburg impedance) the charge transfer resistance

A) increases with dc bias is increased from OCP
B) increases when dc bias is decreased from OCP
C) decreases when dc bias is increased from OCP
D) decreases when dc bias is decreased from OCP

Question 6

The equation that describes Bounded Warburg impedance is

A) $$\frac { \left( \left( \frac { k _ { 1 ak } } { \sqrt { j \omega D _ { A } } } \right) + \left( \frac { k _ { - 1 \dot { ak } } } { \sqrt { j \omega D _ { B } } } \right) \right) } { F \left( \left. b _ { 1 } k _ { 1 \dot { ak } } C _ { A } \right| _ { x =0} - \left. b _ { - 1 } k _ { - 1 \dot { } } C _ { B } \right| _ { x = 0 } \right) }$$
B) $$\frac { \left( k _ { 1 \dot { ak } } \frac { \tanh \left( \left( \sqrt { \frac { j \omega } { D _ { A } } } \right) \delta \right) } { \sqrt { \frac { j \omega } { D _ { A } } } } + k _ { - 1 \dot { ak } } \frac { \tanh \left( \left( \sqrt { \frac { j \omega } { D _ { B } } } \right) \delta \right) } { \sqrt { \frac { j \omega } { D _ { B } } } } \right) } { \left\{ F \left( \left. b _ { 1 } k _ { 1 \dot { ak } } C _ { A } \right| _ { x = 0 } - \left. b _ { - 1 } k _ { - 1 \dot { ak } } C _ { B } \right| _ { x - 0 } \right) \right\} }$$
C) $$\frac { R T } { F ^ { 2 } C _ { A -bulk } \sqrt { j \omega D _ { A } } } + \frac { R T } { F ^ { 2 } C _ { B - bulk} \sqrt { j \omega D _ { B } } }$$
D) none of the above

Question 7

Under semi-infinite boundary conditions, for a simple electron transfer reaction, the concentration oscillations and current oscillations have a phase offset (in radians) of

A) $$\pm \pi$$
B) 0
C) $$\frac { \pm \pi } { 2 }$$
D) $$\frac { \pm \pi } { 4 }$$

Question 8

CPE behavior may be expected when the electrode has

A) 2D heterogeneity only
B) 3D heterogeneity only
C) both 2D and 3D heterogeneity
D) none of the above

Question 9

If CPE exponent is -1, the element is

A) inductor,
B) capacitor,
C) resistance
D) Warburg impedance

Question 10

Consider a porous electrode. E_dc = 0 V vs. OCP, and there is no reaction. When an ac potential is applied, at the pore end (x = l),

A) potential gradient is zero
B) potential amplitude is zero
C) potential amplitude is Eac0
D) none of the above

Question 11

Consider a system which exhibits CPE behavior. Given R_sol = 100 $\Omega$ cm², R_t = R_p = 200 $\Omega$ cm², and CPE parameters Y₀ = 5×10^-5 (rad s^-1)^1-n, n =0.8 , the equivalent capacitance as per Brug's formula is __________ $\mu$ F cm² and as per Hsu & Mansfeld formula is _________ $\mu$ F cm²

Question 12

According to empirical studies, when the CPE parameter Y₀ increases, the value of n

A) increases
B) decreases
C) does not change
D) can either increase or decrease but will not remain the same.

Question 13

If a porous insulating film is present on an electrode surface, the film component may be modeled with a

A) capacitor in parallel with a resistor
B) simple resistor
C) capacitor in parallel with a series combination of resistor and Warburg impedance
D) a simple capacitor

Question 14

In a film, two types of defects that are considered in point defect model are ________ (one word) and interstitial

Question 15

As per PDM, cation interstitials are consumed at

A) metal-film interface
B) film-solution interface
C) both of the above
D) none of the above

Question 16

During anion vacancy creation, the film thickness remains constant

Question 17

PDM employs the following equation to describe mass transfer in the film

A) Fick's second law in one dimension
B) Fick's second law in two dimensions
C) Nernst Planck equation
D) Fromhold-Cook equation

Question 18

CPE can arise from the following distribution of time constants

A) normal
B) logarithmic
C) random
D) normal distribution of logarithmic

Question 19

If CPE exponent is 0, then the element is

A) inductor,
B) capacitor,
C) resistor
D) Warburg

Question 20

A Temkin isotherm model will reduce to Langmuir isotherm when parameter "g" is _____

Question 21

Levich equation can be used to estimate

A) diffusion layer thickness in an RDE
B) fluid boundary layer thickness in RDE
C) temperature boundary layer thickness in RDE
D) diffusivity of a reacting species

Question 22

For a simple electron transfer reaction, with finite diffusion layer thickness (bounded Warburg impedance) the polarization resistance

A) increases with dc bias is increased from OCP
B) increases when dc bias is decreased from OCP
C) decreases when dc bias is increased from OCP
D) decreases when dc bias is decreased from OCP

Question 23

A simple electron transfer reaction, is conducted on a RDE.
-Given that D_A = D_B, and C_A-bulk = C_B-bulk = 50 mM, if the concentration of A on the surface, C_A-s = 20 mM at a given dc potential, then C_B-s = _______ mM

Question 24

A simple electron transfer reaction, is conducted on a RDE.
-In the above equation, if k_1dc = 10^-2 cm/s and k_-1dc = 10^-5 cm/s, then the net faradaic current is ______________ mA/cm² . Remember that 1 M = 1 mol/lit = 10^-3 mol/ cm³.

Question 25

A simple electron transfer reaction with semi-infinite boundary conditions is analyzed using EIS. The polarization resistance of this system is

A) zero
B) infinity
C) finite positive value
D) finite negative value

Question 26

The complex plane plot of a simple electron transfer reaction acquired at multiple dc bias values is given below.
The low-frequency data shows the signature of

A) kinetic limited regime
B) semi-infinite Warburg
C) Bounded Warburg
D) constant phase element

Question 27

Under semi-infinite boundary conditions, for a simple electron transfer reaction, the concentration oscillations and potential oscillations have a phase offset (in radians) of

A) $$\frac { \pi } { 2 }$$
B) $$\frac { - \pi } { 2 }$$
C) 0
D) $$\frac { \pm \pi } { 4 }$$

Question 28

Consider the following reaction $$A \underset { k _ { 2 } } { \stackrel { k _ { 1 } } { \rightleftarrows } } B + e ^ { - }$$
. The concentration of A and B in bulk solution are equal. When a negative dc bias is applied (vs. OCP), under steady-state conditions, on the surface,

A) C_A > C_B,
B) C_A < C_B
C) C_A = C_B
D) it could be any of the above depending on kinetic parameter values.

Question 29

A perfectly insulating film on an electrode surface is best modeled as a ________ (one word)

Question 30

In the usual notation, the expression $$Z = \frac { \rho } { \pi r ^ { 2 } } \frac { \operatorname { coth } ( m \ell ) } { m }$$
is used to calculate

A) semi-infinite Warburg impedance
B) Bounded Warburg impedance
C) CPE impedance
D) porous electrode impedance

Question 31

PDM describes various processes that can occur in a film on the electrode surface. As per PDM, anion vacancies are produced at

A) metal-film interface
B) film-solution interface
C) both of the above
D) none of the above

Question 32

As per PDM, the potential drop across metal-film interface depends on

A) film thickness
B) solution pH
C) both of the above
D) none of the above

Question 33

PDM employs the following assumption to describe mass transfer within the film.

A) the film is a continuous medium
B) film is a lattice
C) film is porous
D) film has an accumulation of ions near interfaces.

Question 34

When a film is present on an electrode surface, sometimes, an inductive loop at mid frequencies is seen in the complex plane plot of EIS data. This can be described using

A) PDM
B) SCA
C) AIC
D) all of the above