Fuel Cell Applications. • Heteropolyacid(HPA)-SiO. 2 nanoparticles for high
temperature operation of a direct methanol fuel cell. • Preparation and ...
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
