1. Electrophoretic Deposition of Cobalt
Ferrite Nanoparticles into 3D Felt
Nicole Shellhammer Pacheco
M.S. Thesis Defense
Chemical Engineering
Committee Members:
Professor Jan B. Talbot, Chair
Professor Joanna M. McKittrick
Professor Justin P. Opatkiewicz
1

2. • Motivation and Objectives
• Background
• Experiments
– Electrophoretic Deposition (EPD)
– Adhesion Tests
– EPD Penetration
– Electrochemical Study
• Results & Discussion
• Conclusions
Outline
Image Source: http://www.aliexpress.com/item/Graphite-felt-custom-made-for-vacuum-
furnace-Insulation-protection/32398127261.html 2

3. Hydrogen as a fuel
• Uses of hydrogen
– Burning hydrogen
– Hydrogen fuel cells
• Advantages of hydrogen as a fuel
– Safe
– Environmentally-friendly
– Can replace fossil fuels used in
transportation systems
• Challenge: 86 % of hydrogen is
produced from burning fossil fuels1
Motivation and Objectives
1Steinfeld, A. International Journal of Hydrogen Energy 2002, 27, 611–619.
Image source: http://www.zmescience.com/science/hydrogen-car-fuel-04042013/ 3

4. Objective
• Produce hydrogen from clean
and sustainable method
– Solar sulfur-ammonia (SA)
thermochemical cycle
Goals
• Penetrate and coat nanoparticles
into 3D felt with EPD
• Improve kinetically slow anodic
reaction for SA cycle with EPD
deposits of electrocatalysts
– Determine EPD conditions and
suspension properties
Motivation and Objectives
Image source: http://www.baseofengineering.com/index.php/2015/06/12/engineers-develop-
state-by-state-plan-to-convert-us-to-100-clean-renewable-energy-by-2050/ 4

5. Background
• Solar sulfur-ammonia (SA) thermochemical cycle
– Oxygen producing thermochemical cycle
– Hydrogen producing electrochemical cycle
Image source: Taylor, R.; Davenport, R.; Talbot, J.; Herz, R.; Luc, W.; Genders, D.; Symons, P.;
Brown, L. Energy Procedia 2014, 49, 2047–2058.
5

6. Hydrogen producing electrochemical cycle:
• Kinetically slow anodic reaction in electrolytic reactor
– Oxidation of ammonium sulfite to ammonium sulfate
Background Electrochemistry
Tanakit, R.; Luc, W.; Talbot, ECS Transactions, 58 (42) 1-9 (2014).
6

7. • Advantages of EPD:
– Simple apparatus
– Short deposition time
– Allows various substrate shapes
Background Electrophoretic Deposition
Image source: Siracuse et al. J. Electrochem. Soc., 137 (1990)
Hamaker equation:
m
Et
Electrophoretic mobility:
7
• Bath properties:
• Dielectric constant of liquid ( ), and
viscosity of liquid ( )
• Surface charge of the particle: zeta
potential ( ) measured
• C is concentration and A is
area of EPD deposit

8. • Filling pores
– Silica nanoparticles into porous
anodic aluminum oxide film
• Penetrate and coat 3D material
– EPD deposited nickel oxide film
into 3D porous nickel foam
Background EPD of 3D Substrates
Fori, B.; Taberna, P.; Arurault, L.; Bonino, J. Journal of Colloid and Interface Science 2014, 413, 31–36.
Gonzalez, Z.; Ferrari, B.; Sanchez-Herencia, A.; Caballero, A.; Morales, J.; Hernan, L. In
Electrophoretic Deposition: Fundamentals and Applications V, Oct. 2015.
8

9. • Penetration equation:
– EPD of 10 nm ceramic dielectric particles
between carbon nanotubes on stainless steel
electrode (50 nm diameter, 20 µm length)
– Ratio of Peclet number to Damköhler number
(electrophoretic velocity (v) to local
deposition rate (k))
Background Penetration by EPD
>1000
Bakhoum, E.; Cheng, M. Journal of Applied Physics 2009, 105, 1–6. 9
a = average pore radius, D = diffusion coefficient, gamma = experimental coefficient

10. Objective: Penetrate and coat 3D felt
and enhance anodic reaction rate for
hydrogen subcycle for SA
thermochemical cycle
– Electrophoretic Deposition (EPD)
– Adhesion Tests
– EPD Penetration
– Electrochemical Study
Experiments
10

11. • Baths: 2 g/L cobalt ferrite
nanoparticles in
– 100 % ethanol (E)
– 100 % acetylacetone with 0.2 wt. %
polyethylenimine (AA-PEI)
– 90/10 % water/isopropanol (IPA)
with 0.05 mM or 1 mM CTAB
(hexadecyltrimethlyammonium
bromide)
Experiments Electrophoretic Deposition (EPD)
11
Desired: Positive zeta
potential > 25 mV
Image: Zi et al., Journal of Magnetism and Magnetic Materials, 321(2009)1251–1255

12. • Substrates:
– 3.14 cm2 of aluminum foil and
graphite paper
– 1 cm2 of 3 mm carbon, 6 mm
graphite felt
• E bath EPD conditions:
– 20 V - 63 V for 1 or 2 min
• AA-PEI bath EPD conditions:
– 60 V - 128 V for 1-13 min
Experiments Electrophoretic Deposition (EPD)
12

13. • Dry adhesion
– Important for removing and drying deposit from
bath
– Tape test: place on film and remove scotch tape
• Wet adhesion
– Important for electrochemical tests of deposits
– Soak test: 24 hour soak of deposits in de-ionized
water
Experiments Adhesion Tests
13
Adhesion of EPD deposits from ethanol bath on
aluminum foil (weight of sample before & after test)

14. • Penetration calculation into porous carbon
– Ratio values based on EPD conditions and suspension properties
– Ratio > 1000 means deep penetration can occur into felt
• Phillips XL30 ESEM scanning electron microscope
(SEM) imaging of EPD deposits (Neil Verma)
– Image analysis of top and middle of the 3D felt deposits
Experiments EPD Penetration
Image source: http://sirius.mtm.kuleuven.be/Research/Equipment/fiches/xl30-esem-feg.html
14

15. • Linear sweep voltammetry of EPD deposits
– Oxidation of 2 M ammonium sulfite to ammonium sulfate
– Deposits soaked in 2 M ammonium sulfite before (24 or 72 hr)
– Princeton Applied Research VersaSTAT 3 potentiostat
• Scanned from 0.0 to 1.0 V vs. standard calomel electrode (SCE)
• Sweep rate of 50 mV/s
• Standard three-compartment electrode cell
Experiments Electrochemical Study
15
Image source: http://electronicstructure.wikidot.com/oxygen-reduction-reaction-
on-platinum-using-dft
8 cm2 graphite cloth
1 cm2 deposit on 3 mm or 6 mm felt
Standard calomel
electrode (SCE)

16. • Calculation of monolayer deposit density: 10.2 μg/cm2
– Assume hexagonal close packing (91 % area filled)
– 20 nm cobalt ferrite particles into 4.91 cm2 area
• EPD from ethanol bath: 5 V for 55 s on aluminum foil
Results Electrophoretic Deposition (EPD)
0
2.5
5
7.5
10
12.5
15
0 10 20 30 40 50 60
DepositDensity(µg/cm2)
Time (s)
1 monolayer
16
500 nm

17. • Dry adhesion test (Tape test)
– 0 to 25 % of the particles were removed
– Error: ± 0.01 mg
• Wet adhesion test (24 hour soak test)
– No particles were removed
Results Adhesion Tests
17

18. • EPD on graphite paper (GP) follows Hamaker equation
• 3 mm and 6 mm felt may have adsorption of nanoparticles
with no electric field (not verified experimentally)
• Deposit density greater for 6mm > 3mm > GP
Results EPD from Ethanol bath
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
0 10 20 30 40 50 60 70
DepsoitDensity(mg/cm2)
Voltage*Time (V*min)
GP
3 mm felt
6 mm felt
Slope ratios:
3 mm to GP: 1.3
6 mm to GP: 1.7
6 mm to 3 mm: 1.4
18

19. EPD follows Hamaker equation
Deposit density greater for Al, GP > 6mm > 3mm
Results EPD from AA-PEI bath
Slope ratios:
Al to 3 mm: 5.6
GP to 3 mm: 5.6
Al to 6 mm: 2.2
GP to 6 mm: 2.2
6 mm to 3 mm: 2.6
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0 500 1000 1500 2000
Depsoitdensity(mg/cm2)
Voltage*Time (V*min)
Al
GP
3 mm felt
6 mm felt
19

20. • Electrophoretic velocity to local deposition rate into 6 mm
felt:
– EPD conditions: E, 40 V, 1 min (41 mA, 1.17 mg)
– EPD conditions: AA-PEI, 127 V, 4 min (6 mA, 0.79 mg)
Results EPD Penetration
20Bakhoum, E.; Cheng, M. Journal of Applied Physics 2009, 105, 1–6.
= 8 x 104 >1000
Deep penetration of 3D felt up to 6 mm thick should occur
= 5 x 106 >1000
>1000

21. Blanks
3 mm carbon felt 6 mm graphite felt
Results EPD Penetration
21

22. 3 mm carbon felt
EPD deposit conditions: E, 40 V, 1 min, (42 mA, 0.68 mg)
Top of the deposit Middle of the deposit
Results EPD Penetration
22

23. 6 mm graphite felt
EPD deposit conditions: E, 40 V, 1 min (41 mA, 1.17 mg)
Top of the deposit Middle of the deposit
Results EPD Penetration
23

24. • Deposit weight and number of monolayers
– E and AA-PEI bath
• Maximum monolayers: 27 on graphite paper, 1 on 3 mm felt
• Maximum surface coverage of 6 mm felt: ~31 %
Results Comparison of EPD baths
24

25. • Linear sweep voltammetry (LSV) from 0 to 1.0 V vs. SCE
with scan rate of 50 mV/s in 2 M ammonium sulfite
– As reaction increases, i proportional exp(V)
– Deposit from ethanol bath into 6 mm graphite felt
– EPD conditions: 40 V, 1 min, (41 mA, 1.17 mg)
Results Electrochemical Study
25
i
iblank

26. • Extrapolated current density of platinum electrode at 0.8 V
vs. NHE for 50 mV/s in 2 M ammonium sulfite solution1
imax = 190 mA/cm2
Results Electrochemical Study
261Skavas, E.; Hemmingsen, T. Electrochimica Acta 2007, 52, 3510–3517.
• EPD conditions into 6 mm felt with highest electrochemical activity
• AA-PEI bath: 127 V for 4 min
• E bath: 40 V for 1 min

27. EPD Deposits from Ethanol bath
• Ratio current density of deposit compared to blank
substrate vs. deposit density
– i/iblank for graphite paper and 6 mm felt is ~1.6
– i/iblank for 3 mm felt ranges between 4-8
Results Electrochemical
0
1
2
3
4
5
6
7
8
9
0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40
i/iblank
Deposit Density (mg/cm2)
GP
3 mm felt
6 mm felt
27

28. EPD deposits from AA-PEI bath
• Ratio current density of deposit compared to blank
substrate vs. deposit density
– i/iblank for aluminum foil, graphite paper and 6 mm felt is ~1.9
– i/iblank for 3 mm felt ranges between 9-14
Results Electrochemical
28
0
2
4
6
8
10
12
14
16
0.0 1.0 2.0 3.0 4.0 5.0
i/iblank
Deposit density (mg/cm2)
Al
GP
3 mm felt
6 mm felt

29. • Full penetration and coating of 3 mm and 6 mm felt
• Maximum number of monolayers deposited
– Graphite paper: 27
– 3 mm carbon felt: 1
– 6 mm graphite felt: < 1
• Current density of EPD deposit into 6 mm felt compared to
platinum electrode
– 32 % imax from AA-PEI bath (127 V for 4 min)
– 20 % imax from ethanol bath (40 V for 1 min)
• Ratio of current density of deposit to blank substrate
– Highest magnitude for 3 mm carbon felt
Conclusions
29

30. • Wet adhesion on graphite paper, 3 mm, and 6 mm felt
• Determine EPD conditions for 1 monolayer of
particles into 6 mm graphite felt
• Determine how number of monolayers affect
electrochemical activity of EPD deposits (Neil Verma
M.S. thesis)
Future work
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31. • Professor Jan B. Talbot (UCSD)
• Neil Verma for SEM image analysis (UCSD)
• Dr. Richard Herz (UCSD)
• Dr. Dave Genders and Dr. Peter Symons
(Electrosynthesis Inc.)
• Dr. Lloyd Brown (Thermochemical Solutions LLC.)
• Roger Davenport and Robin Taylor (Leidos)
This work was funded by the Department of Energy,
Grant DE-FG36-07GO17002.
Acknowledgements
31

32. Thank you!
Committee Members:
Professor Jan B. Talbot, Chair
Professor Joanna M. McKittrick
Professor Justin P. Opatkiewicz
32