Nano Material Applications
in Fuel Cell
Dept. of Chemical Eng. Yonsei Univ.
Prof. Y.G. Shul, H.S. Kim
Nano Materials in Fuel Cell
• Hydrogen
Release Catalyst
• Novel Anode Catalyst
• Organic-Inorganic
Membrane
Fuel Cell Applications
• Heteropolyacid(HPA)-SiO2 nanoparticles for high
temperature operation of a direct methanol fuel
cell
• Preparation and characterization of new carbon
for fuel cell application
• Pulse Electrodeposition for Preparing PEM Fuel
Cell Electrode
• Investigation of alloy catalyst for accelerating
hydrogen release from NaBH4
In this study
• Preparation nanohybride particle (HPA/SiO2)
By micro emulsion technique
SiO2
.
.. ... ....... ... .. .. .
. .......... . .
.
.. . .
.. ... ............... .......... . . .
. . .... ...... . . .
.
.
.
. . .
.. ... .. ............. ............ .. .. .
. .. . .... ... .... . . .
Nano scale
Heteropoly acid
• Characterization :
TEM, Solid state NMR, TMP adsorption, N2 adsorption, FT-IR
Heteropolyacid-SiO2 nanoparticles
100 nm
TEM image of heteropolyacid-SiO2 nanoparticle
(R=2, X=30%, 12hr)
R= [H2O]/[AOT]
X=[Heteropolyacid]
100nm
TEM image of heteropolyacid-SiO2 nanoparticle
(R=2, HPA 30%, 24hr)
31P
MAS NMR
H3PW12O40•6H2O
Dehydration of heteropolyacid
-15.6ppm
Heteropolyacid < nanoparticle < Bulk powder
Dehydration
Trapping of acidic proton to OH group
Heteropolyacid
-15.3ppm
100nm
-15.1ppm
[ PW12O40 ]3−
500nm
-15.0ppm
H+
OH
H+
OH
H+
OH
Si
Si
Si
Bulk
-10
-12
-14
-16
-18
-20
Chemical shift (δ, ppm)
Fig. 31P MAS NMR spectra of heteropolyacid and HPA/SiO2
Referenced from
- M.Misono et al., J.Phys.Chem.B., 104 (2000) 8108
- F.Lefebvre et al., J.Chem.Soc.Chem.Commun, (1992) 756
13C
CP MAS NMR
27.9 ppm
(a)
18.2 ppm
11.4 ppm
54.0 ppm
(b)
60
50
40
30
20
10
0
Chemical shift (δ, ppm)
13C
CP MAS NMR spectra
(a) thiol- and (b) sulfonic-functionalized heteropolyacid-SiO2 nanoparticle.
Preparation of inorganic particles
in microemulsion
Aerosol-OT
O
O
O
H2O
HPA
+
SO3 Na
O
Sol-gel process
Si(OR)4 + 4H2O → Si(OH)4 + 4ROH
Si-OH + HO-Si → Si-O-Si + H2O
Cyclohexane
TEOS
Surface area vs. nano HPA/SiO2
0.05
600
0.9
0.04
400
DV/DR (cm3/g)
2
BET Surface area (m /g)
500
Pore fraction
0.8
300
200
0
Pore ratio
R < 1nm
0.6
0.5
0.4
0.3
R > 3nm
0.2
0.03
0.1
1
100nm HPA/SiO2
500nm HPA/SiO2
Bulk HPA/SiO2
0.02
Surface area
Bulk
2
3
500nm 100nm
Pore size distribution
0.01
100
0.7
0.00
1
HPA
2
Bulk
3
500nm
4
100nm
0
20
40
Pore size (A)
60
80
Application to DMFC
Pressure gauge
Cell
Fuel pump
flowmeter
2way
valve
Needle
valve
6 way
valve
Methanol
2M solution.
O2
Tank
Fuel heater
G.C
• Heteropolyacid
→ Proton conductivity
• Silica particle
→ Methanol blocker
Polysulfone/nanoparticle composite
membrane
100
(a)
1.4 ×10-3 S/cm
18
6.5×10-5 S/cm
(b)
16
80
Heteropolyacid-SiO2 nanoparticle
40
20
Methanol crossover rate
(µmol / cm2 min)
14
60
Z''(ohm)
Sulfonated polysulfone membrane
Composite membrane
Heteropolyacid-SiO2 nanoparticle
12
10
8
6
4
2
0
45
50
55
60
65
70
75
80
Z'(ohm)
85
90
95
100 105 110
0
20
40
60
80
100
120
Cell temperature (oC)
Complex impedance response(a) and methanol crossover rate(b) of the sulfonated polysulfone
and sulfonated polysulfone / heteropolyacid – SiO2 nanoparticle composite membrane.
140
Nafion/nanoparticle composite membrane
100
10
Crossover rate (µmol/cm2*min)
2
conductivity x10 (S/cm)
8
6
Nafion membrane
Composite membrane
(b)
(a)
A little decrease of proton conductivity
4
2
80
60
40
Reduction of methanol crossover
20
0
0
0
5
10
15
Content of nanoparticles (%)
20
25
0
20
40
60
80
100
120
140
Temperature (oC)
Proton conductivity(a) and methanol crossover rate(b) of the sulfonated polysulfone
and sulfonated polysulfone / heteropolyacid – SiO2 nanoparticle composite membrane.
160
Nafion-HPA/SiO2 composite membrane
(Nafion / sulfonated heteropolyacid-SiO2 nanoparticle composite membrane)
H2O
H3O+
80 oC
160 oC
200 oC
50
Cell voltage (V)
Sulfonated heteropolyacid - SiO2 nanoparticle
60
40
2
0.6
Heteropolyacid - SiO2 nanoparticle
40
30
0.4
20
0.2
20
0
4000
10
0
0.0
3500
3000
2500
2000
1500
1000
-1
Wavenumber (cm )
FT-IR spectra of sulfonated heteropolyacid-SiO2 nanoparticle
Power density (mW/cm )
80
Transmittance (%)
60
0.8
100
0
50
100
150
200
250
Current density (mA/cm2)
DMFC performance of composite membrane
Improvement of DMFC performance by increasing the cell temperature
300
Research of carbon material application
Caron
structure
FC
application
Performance
remark
Reference
Pt/CNT
PEMFC
0.7V,
0.7 mA/cm2
(50oC)
high electrocatalytic activity for oxygen reduction
3.6±0.3nm
J.of power
sources
139(2005) 73
Pt/mesopor
ous carbon
(SBA-15)
DMFC
0.4V,
135 mA/cm2 (65oC)
Great potentiality for DMFC support
Johnson Mattheyat
0.4V, 135 mA/cm2 (80oC)
J.Of power
sources
130 (2005)
PtSn/
MWNT
DEFC
0.4V,
100 mA/cm2
Improvement in liquid mass transfer for catalyst3nm
PtSn/XC-72
0.4V, 80 mA/cm2
Carbon 42
(2004)
Carbon
fiber
Mg-H2O2
Semi-fuel
cell
1.5V,
300mA/cm2
Similar reference with Pt-Ir on carbon paper
Mg: anode
Microfiber carbon :cathode
cathode side: 0.20M H2O2
J.Of power
sources 96
(2001) 240
Carbon
nanocoil
DMFC
0.4V ,
170mA/cm2
(60oC)
Great potentiality for DMFC support material
Angew. Chem
2003,115,
4488
Carbon
nanohorn
DMFC
0.4V ,
130mA/cm2
NEC
I-V curve for electrodes with commercial
Pt/C and Pt/C+ Pt/ACF (900℃)
1.1
1.0
Commercial Pt/C
Commertial Pt/C (70%)+ Pt/ACF(30%.400oC)
Commertial Pt/C (70%)+ Pt/ACF(30%.900oC)
0.9
Voltage ( V )
0.8
0.7
0.6
0.5
0.4
Performance increasing
0.3
0.2
0.1
0.0
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
Current density ( A/cm2 )
Current density ( mA/cm2 )
Commercial Pt/C
Pt/C+Pt/ACF (400℃)
Pt/C+Pt/ACF (900℃)
710
807
960
Cell Temp. : 80℃, Humidify condition : RH% 100 anode and cathode, Flow rate: Stoichiometry 1.5(Anode):2.0(Cathode)
Impedance for the electrodes manufactured
with Pt/C, Pt/ACF(900℃) catalysts
0.10
0.30
o
Pt/ACF ( 400 C )
Pt/ACF ( 900oC )
0.08
Pt/ACF ( 400oC )
Pt/ACF ( 900oC )
0.25
-Z'' / O hm
-Z'' / O hm
0.20
0.06
0.04
0.15
0.10
0.02
0.05
0.00
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
0.22
Z' / Ohm
Impedance spectra at 0.7V
0.24
0.26
0.00
0.0
0.1
0.2
0.3
0.4
Z' / Ohm
Impedance spectra at 0.8V
0.5
Specific surface area and average pore
diameter of the CNF treated by KOH
CNF
5H
Activation condition
Surf. area
(m2 /g)
Avg. Pore diameter
(Å )
No activation
107.60
62.21
750-1h
444.18
46.07
800-1h
509.95
48.80
900-1h
645.53
48.0
900-2h
460.10
44.33
Modified method
375.52
54.41
900-3h
341.87
62.37
950-1h
303.54
58.01
SEM - CNFs named 5H
pristine
800-1h
900-2h
MDF(900-2h)
TEM - 60wt% Pt-Ru/CNF
A/(900-2h)
(a)
B/(900-2h)
(b)
50 nm
B/MDF(900-2h)
(c)
50 nm
50 nm
Growth of nanofiber on ACF
micropores
Surface and Pores of
Activated Carbon Fiber
H2
C2H4
Impregnation of metal salt solution
a
c
b
a, b
Reduction in He/H2
Synthesis from C2H4/H2
inactive
Preparation of various carbon substrates
• CNF/ACF
Fig. SEM images of carbon nano fibers grown on ACF
Preparation of platinum on ACF-CNFs
TEM Image of Pt/ACF-CNFs
Fig. TEM images of Platinum oncarbon nanofibers grown on ACF
Preparation of platinum on ACF-CNFs
XRD patterns of Pt/ACF-CNFs
Pt(1 1 1)
P t/A C F -C N F s
P t/C ( C o m m e r c ia l)
Pt(2 0 0)
Intensity(a.u.)
Pt(2 2 0)
30
40
50
60
2 th e ta
Fig. XRD pattern of Pt/ACF-CNFs
70
80
Single cell performance
1.0
Pt/ACF-CNFs 30%
Pt/C
Pt/ACF-CNFs 20%
Pt/ACF-CNFs 100%
0.9
Voltage(V)
0.8
0.7
0.6
0.5
0.4
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Current density(A/cm 2 )
Fig. The performance of Pt/ACF-CNFs used in anode catalyst
Cell Temp. : 80℃, Humidify condition : RH% 100 anode and cathode, Stoichiometry anode: cathode = 1.5: 2.0
Membrane : nafion 112:, anode : 20%Pt/C, cathode : 20%Pt/C and 20%Pt/ACF-CNFs+20%Pt/C, Back pressure : 1bar
Pulse Electrodeposition for Preparing PEM
Fuel Cell Electrode
• Objectives
– Reducing cost of electrode by decreasing Pt loading
– Decreasing particle size
– localizing Pt on the surface of electrode in contact with
membrane and increasing efficiency of Pt
• Advantages of pulse electrodeposition
– Low cost
– Easy of control
– Versatility
Schematic Diagram of The Electrode
Prepared by Pulse Electrodeposition
Catalyst particle
Reactant gas
Ion exchange
membrane
Carbon clothe
Hydrophobic
carbon layer
Hydrophilic
carbon layer
Back-Scattered Electron Image and Pt Line
Scan of The Cross Section of MEA using
EPMA
membrane
PC layer
E-TEK Pt/C layer
E-TEK GDL
200.0
GDL
Pt
membrane ETEK layer GDL
100.0
PC deposition Pt/C layer
0.0
0.0
Distance
Microne(µm)
161.0
ESEM Image and Pt Concentration Profile of
the Cross Section of MEA Using EDX Spot
Analysis
80
E-TEK electrode
60
Membrane
Pt wt%
PC deposition electrode
40
E-TEK electrode
PC deposition electrode
20
0
0
2
4
6
8
10
Distance from membrane (µm)
12
14
Comparison of MEA performance between
pulse electrodeposited electrode and TKK
1.0
2
TKK (0.4mg/cm )
2
PC (0.32mg/cm )
0.9
Potential (V)
0.8
0.7
0.6
0.5
0.4
0.3
0.0
0.3
0.6
0.9
1.2
1.5
1.8
2
Current density (A/cm )
2.1
2.4
2.7
High Throughput Screening (HTS) test
• Hydrogen release rate of metal catalysts can be
measured without catalyst synthesis procedure
• To apply metal alloy catalyst, amounts of precursor
solutions can be mixed to accurate ratios.
Mixed
Precursor
Solution
RuCl3
Co(NO3)2
FeCl2
..
H2
NaBH4
Reduction
H2
Coolant
Hydrolysis
Schematic diagram of simplified HTS test microreactors
Coolant
-1 -1 )
(Lmin g
ation Rate
er
en
G
n
Hydroge
Ru:Co:Fe = 60:20:20
(wt%)
30
30
25
25
Rate
Generation
Hydrogen
-1 -1 )
(Lmin g
Hydrogen release test (Ternary alloy)
20
15
10
5
0
20
15
10
5
0
Ru
Ru
Co
Ni
Co
Fe
Hydrogen release rate of (a) Ru-Co-Ni, (b) Ru-Co-Fe
from 10 wt% NaBH4 solution with 4 wt% NaOH
(Temperature fixed to 25°C)
XRD Patterns
• Co and Fe were not
reduced completely
when NaBH4 only was
used for reduction.
• After the additional
reduction by using
hydrogen, CoFe alloy
were shown
CoFe2O4
RuCoFe
Intensity
(c)
(b)
(a)
30
40
50
60
70
2 theta
XRD Patterns of (a) Ru/ACF; (b) NaBH4-reduced
Ru0.6Co0.2Fe0.2/ACF; (c) NaBH4 and H2-reduced
Ru0.6Co0.2Fe0.2/ACF catalyst
RuCoFe/ACF nanocatalyst
100
(e)
80
3.0
(d)
(c)
60
2.5
ln k
H2 Release Rate / L min-1gRu-1
3.5
(b)
40
(e)
2.0
(d)
(a)
(c)
1.5
20
(b)
1.0
(a)
0
10
15
20
25
30
35
40
3.20
3.25
3.30
T / oC
3.35
3.40
3.45
3.50
1000 / T
hydrogen release rate
at 25 °C (Lmin-1gRu-1)
Activation Energy
(kJmol-1)
H2
14.21
59.23
16 wt% Ru0.6Co0.2Fe0.2/ACF
H2
22.63
47.91
16 wt% Ru0.6Co0.2Fe0.2/ACF
NaBH4
34.37
50.54
13 wt% Ru0.75Co0.25/ACF
NaBH4 + H2
37.12
45.44
16 wt% Ru0.6Co0.2Fe0.2/ACF
NaBH4 + H2
41.73
44.01
catalyst
Reduction
Agent
(a
)
(b
)
(c)
10 wt% Ru/ACF
(d
)
(e
)
Conclusions
Nano materials may lead to drastic improvement in fuel cell
application
1)Nanohybride electrolyte (HPA-SiO2+Nafion®) was
effective for the high temperature operating of DMFC
2)New nano carbons are promising to enhance the catalytic
activity in fuel cell
3) Nano alloy will be effective to release control of the H2
from chemical hydride (NaBH4, NH3BH3)
4) Electrodeposition is effective to reduce the amount of Pt
loading
Acknowledgement
Backup slides
Impedance spectra
0.10
Pt/ACF-CNFs 30%
Pt/C
Pt/ACF-CNFs 20%
Pt/ACF-CNFs 100%
-Z''/Ohm
0.08
Membrane resistance
0.063Ω
Interfacial resistance
(Mixture ratio 20%Pt/C:20%Pt/ACF-CNFs)
0.06
0.04
0.02
0.00
0.05
0.10
0.15
0.20
Z'/Ohm
Fig. Impedance spectra of single cell
0.25
Only 20% Pt/C
0.069Ω
Only 20% Pt/ACF-CNFs
0.175Ω
2:8
0.096Ω
3:7
0.065Ω
Cyclic voltammogram
0 .4
0 .2
0 .0
i/A
-0 .2
-0 .4
-0 .6
P t/C
P t/A C F -C N T s 3 0 %
-0 .8
-1 .0
-0 .2
0 .0
0 .2
0 .4
0 .6
0 .8
1 .0
1 .2
E /V
Fig. Cyclic voltammograms of Pt/ACF-CNFs used oxygen
Technical Barriers of Electrodes for PEM
Fuel Cells
¾ Electrode performance
• 400 mA/cm2 at 0.8V with H2/Air and 1atm
• Novel method of pulse electrodeposition
• Pt-X alloy
¾ Material Cost
• 0.2 g (Pt loading)/peak kW
• Non-precious catalyst (Pt-free)
¾ Durability
• 40,000 hours operation with <10% performance degradation
in stationary applications.
Why Pulse Electrodeposition
(Dependence of Nucleation Rate on
Overpotential)
Rate of 2D-nucleation * Tafel expression for overpotential
η = α + β log i
 −bsε 2 
J = K1 exp 

 zekTη 
•
•
•
•
•
Pulse electrodeposition
•Off time
•Concentration of electrolyte is recovered
•Electrodeposition at high current density
Current
density
θ
θ2
θ1
ip
ia
time
t1
t2
t3
t4
t5
•
•
•
•
•
•
•
•
•
•
K1 - rate constant
S - surface area occupied by one
atom on the surface of the nucleus
e - the charge of the electron
z - the electronic charge of the ion
k - the Boltzmann constant
T - the temperature
b=P2/4S, where P is the perimeter and
S is the surface area
i – current applied
α, β – Tafel constants
η – Overpotential
θ1: on time
θ2: off time
Ip: peak current density
Ia: average current density
Duty cycle: θ1/ θ
Comparison of the Limiting Current Density
between Pulse and Direct Electrodeposition
diffusion model by H. Y. Cheh,
θ1
= 0.2
θ
(i )
p l
(idc )l
0.4
0.6
0.8
1.0
(i )
p l
( idc )l
=
aθ
aθ
1
exp ( 2 j − 1) aθ  − 1)
(
8
1


1−
⋅
∑
π
( 2 j − 1) ( exp ( 2 j − 1) aθ  − 1)
2
∞
2
j =1
2
2
2
a = π 2 D / 4δ 2
(sec −1 )
TEM and SEM image of Pt electrodeposited
electrodes
Pulse
DC
Polarization Curves of MEAs Prepared by
Direct Current and Pulse Electrodeposition
1.0
0.9
2
50mA/cm DC
200mA/cm2 PC
0.8
Potential (V)
0.7
0.6
0.5
0.4
Nafion 112
Cell Temperature: 75 oC
H2/O2 (flow rate: 1.5/2 stoichiometric)
Pressure: 1atm
0.3
0.2
0.0
0.3
0.6
0.9
1.2
1.5
1.8
2.1
2.4
2
Current density (A/cm )
The conditions of pulse electrodeposition: 200mA/cm2 of peak current density,
5.2ms on time and 70ms off time. Total charge is fixed at 6C/cm2 on both cases.
SEM Images of Pt Electrodeposited
Electrodes by D.C or P.C mode. (Total
charge is fixed at 6C/cm2 on both cases)
50mA/cm2 of D.C. electrodeposition
200mA/cm2 of peak current density,
5.2ms on time and 70ms off time
Effect of the peak current density of pulse
electrodeposition on the performance of the
PEM fuel cell
1.0
10 mA/cm2 DC
30 mA/cm2 PC
100 mA/cm2 PC
200 mA/cm2 PC
400 mA/cm2 PC
2
600 mA/cm PC
0.9
0.8
Potential (V)
0.7
0.6
0.5
0.4
0.3
0.2
0.0
0.3
0.6
0.9
1.2
1.5
1.8
Current density (A/cm2)
2.1
2.4
2.7
Cyclic Voltammograms of the Electrodes
Prepared at Different Peak Current
Densities in Pulse Electrodeposition
1.0
2
Current density (mA/cm )
0.5
0.0
600mA/cm2
-0.5
30mA/cm2
400mA/cm2
200mA/cm2
-1.0
100mA/cm2
-1.5
-0.8
-0.6
-0.4
-0.2
0.0
0.2
Potential (V. Hg/Hg2SO4)
0.4
0.6
0.8
Effect of Charge Density on the
Performance of PEM Fuel Cell
1.0
2
6C/cm
2
8C/cm
2
13C/cm
16C/cm2
0.9
0.8
Potential (V)
0.7
0.6
0.5
0.4
0.3
0.2
0.0
0.3
0.6
0.9
1.2
1.5
1.8
2.1
2
Current density (A/cm )
2.4
2.7
3.0
Comparison of Pt line scan image in the
cross section of the MEA
(A) 8C/cm2 and (B) 20C/cm2
Cps
Cps
300
300
(A)
(B)
0
0
40
0
Microns (μm)
40
0
Microns (μm)