Fuel Cell & Hydrogen Technologies JP
SP2: Catalyst and Electrodes
Borovetz, Bulgaria
June 2nd and 3rd 2014
Intermediate temperature and pressure
electrochemical reactors
EERA FCH2-SP2 WORKSHOP in frame of EIA10
Bridging experimental and numerical research:
development and optimization of advanced characterization tools – Electrochemical Impedance Spectroscopy
Christodoulos Chatzichristodoulou
Technical University of Denmark, Department of Energy Conversion and Storage
Outline
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Motivation
Electrolytes
Cell concept
Electrochemical testing equipment
H2O electrolysis
Summary
Outlook
EERA FCH2 SP2 Workshop
7/9/2014
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Motivation - Sustainability
• Increasing need for large scale, efficient and affordable
storage of intermittent renewable energy
• Need for sustainable production of fuels for transportation
• Need for sustainable production of chemicals
• Oxygenates (MetOH, EtOH, DME) offer high energy density
and ease of storage (as liquids)
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Motivation – Process conditions
Advantages of operating at T ~ 100-300 C, P ~ 10-100 atm:
1. Incorporation of electrolysis and fuel synthesis in a single component.
(System simplicity, reduction of capital cost, intelligent heat management)
2. Improved electrode performance. No need for expensive electrocatalysts.
(Reduction of capital and operating cost)
3. Production of pressurized fuel (and O2). No need for compressor.
(Reduction of capital cost)
4. Use of aqueous electrolytes with gas diffusion electrodes.
(Improved mass transport. Reversible operation)
5. Increased electrolyte conductivity.
(Reduced ohmic losses)
6. Reduced thermal strain, inter-diffusion and catalyst coarsening as
compared to SOEC.
(Durability and lifetime improvement. Easier integration with RE sources)
EERA FCH2 SP2 Workshop
7/9/2014
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Motivation – Some facts
• Many HxCyOz are thermodynamically stable up to about 300
C and very few are stable at much higher temperature
• CH4 may be synthesised using a Ni catalyst (CO + 3 H2 
CH4 + H2O) between 200 – 450 C at 30 bar
• (CH3)2O synthesis on Cu/ZnO/Al2O3 catalyst (2 CO + 4 H2 
(CH3)2O + H2O) between 200 - 300 C at ca. 50 bar, very
similar for synthesis of CH3OH
• Electrochemistry under pressure of 30 - 50 bar and
temperatures of 200 – 300 C  intimate thermal integration
of electrochemistry and catalysis is possible
EERA FCH2 SP2 Workshop
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Electrolytes – The Norby gap
T. Norby, Solid State Ionics, 125 (1999) 1
EERA FCH2 SP2 Workshop
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Electrolytes – Possibilities
• 45 wt% KOH immobilized in ca. 50 % porous ceramics: 0.84 S cm-1
at 200 C and 25 bar
F. Allebrod, C. Chatzichristodoulou, P.L. Mollerup, M.B. Mogensen, Internat. J. Hydrogen Energy, 37 (2012)
16505, and Proc. of 4th EFCF, paper A0705
• 15 wt% K2CO3(aq.): 0.57 S cm-1 at 200 C measured, ca. 0.3 S cm-1
expected for immobilized electrolyte
P.L. Mollerup, A.S. Christiansen, N. Bonanos, M.B. Mogensen, submitted for publication 2013
• Solid acid, CsH2PO4: ca. 10-2 S cm-1 at 240 C (“the limit”).
S.M. Haile, C.R.I. Chisholm, K. Sasaki, D.A. Boysen, T. Uda, Solid acid proton conductors: from laboratory
curiosities to fuel cell electrolytes, Faraday Discussions, 134 (2007) 17
• Acceptor doped metal phosphorous oxides such as Ce(PO3)4 and
CeP2O7 - high initial conductivity – not stable over time > 100 h
C. Chatzichristodoulou, J. Hallinder, A. Lapina, P. Holtappels, M. Mogensen, J. Electrochem. Soc., 160
(2013) F1
• BaCexZryYzO3-δ might be possible at 300 C if its grain boundary
resistance could be reduced – it can by adding ceria, which makes
the material degrade fast in CO2
EERA FCH2 SP2 Workshop
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Electrolytes – Immobilized KOH (aq.)
F. Allebrod et al., Internat. J. Hydrogen Energy, 37 (2012) 16505
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Cell concept
• Aq. electrolyte immobilized in
mesoporous ceramic matrix
Alkaline (KOH) electrolyte (water electrolysis):
• Gas diffusion electrodes
e-
O2
e-
H2O
OH-
O2
H2
Proton conducting
(solid acid) electrolyte:
Aqueous KOH/K2CO3 electrolyte (co-electrolysis):
Ceramic powder, e.g.
SrTiO3, forming a
mesoporous matrix
CO2, O2, CO
H2O2
e-
e-
CO2, H2O
H2O
e-
e-
CO2
H+
CO32-
CO2, O2, CO
H2O2
HCO3
-
O2, H2O
CH3OH, CO2, H2O, …
CH3OH, H2O, CO2, …
EERA FCH2 SP2 Workshop
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Electrochemical testing equipment – Intermediate temperature
and pressure rigs
Ventilation
270° valve
On/off valve
P1=70-100 bara
NC
CO2
V01A
MV-01
NC
V-01B
P-01
MFC-01
V02A
MV-02 V-02B
P-02
MFC-02
C-01A
NC
O2
MV-03A NV03B
P-03
Flow controller
C-03
~2 bara
air supply
V-13
liquid transfer line
transfer line
1/8”
P-04
MFC-04 C-04A
150 °C transfer line
PRV-11
1/16”
V-04D 1/16”
MFC-05
6
MS
R12
C-05
1/8”
7 3
5 1
C-14
PS-12
7/8”
0
1/8”
P-12
CB-01
203.2 mm
Wall panel
Outside 252
Inside GHC
G-03 O2
CB-14
PCV-14
ET-13
1/8”
H2, CO,
CO2(g),
N2, O2,
H2O(g), NH3,
CH4
Pressure controlling valve
Pressure sensor
Electropneumatic transducer
Gas detector
Catalytic burner
3-way valve
Sample holder
Autoclave
20-300°C
1-100 bara
Pressure reduction valve
NC
FL-14A
Ø63.5 mm
MS
MV-14
H2O(l),
CxHyOz(l)
C. Chatzichristodoulou et al., Rev. Sci. Instrum. 84 (2013) 054101-12.
EERA FCH2 SP2 Workshop
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Pressure relief valve
Exhaust outside 252
V-04B
Check valve
50 °C sf transfer line
1/8”
MV-04A V-04A
Magnetic valve, NC/NO
G-02 CO
C-01B
NC
H2
C-02A
VC-02B
02C
MFC-03
V04C
V03A
Needle valve
NC
G-01 H2
V-01C
V03C
N2
1bara
1-100 bara
Mass Spectrometer
Manometer
Electric signal
FL-14B
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H2O electrolysis - Performance
Current density [A•cm-2]
240 °C
40bar
1.5 V
1.75 V
Ag-Ni-foam /
Inconel-foam
0.9
2.00
Ni-foam /
Inconel-foam
0.68
1.58
2xAg-Ni-foam /
2xInconel-foam
0.52
1.38
2xNi-foam /
2xInconel-foam
0.46
1.1
H2 electrode: Inconnel foam based
Electrolyte: KOH (aq.)
O2 electrode: Ni foam based
F. Allebrod et al., J. Power Sources 229 (2013) 22-31
EERA FCH2 SP2 Workshop
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H2O electrolysis - Performance
H2 electrode:
Mo-activated Inconnel foam
Electrolyte:
45 wt% KOH (aq.)
immobilized in mesoporous
SrTiO3
O2 electrode:
Co-activated Ni foam
F. Allebrod et al., J. Power Sources 255 (2014) 394-403
C. Chatzichristodoulou et al., Rev. Sci. Instrum. 84 (2013) 054101-12.
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H2O electrolysis - Degradation
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H2O electrolysis - Upscaling
50 mm
• Continuous production of mesoporous
YSZ layer has been achieved by tape
casting
• Layer thickness 300 μm
full cell height can be < 1mm
• A 5x5 cm2 cell corresponds to ~100 W
at ηel = 85 %
H2 production of > 25 L/h
EERA FCH2 SP2 Workshop
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Summary
• Electrochemical reactors operating at ca. 100-300 °C
and 10-100 bar appear very promising
• Immobilized liquid electrolytes can fill the Norby gap
(0.84 S/cm at 200 °C)
• Encouraging results achieved with H2O electrolysis (2.3
A/cm2 at 1.75 V)
• Efforts to upscale production have begun
• Potential for synthesis of HxCyOz with similar type
electrochemical reactors
EERA FCH2 SP2 Workshop
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Outlook
• Use of oxide based electrocatalysts for the O2-electrode
(DFT + advanced characterization)
• Model assisted electrode development work
• Advanced characterization of GDE functionality
• Corrosion resistant materials for interconnects, current
collectors, stack housing
• Up-scaling fabrication
• Testing of cells, single repeating units and small stacks
• Stack design and testing
• System design
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Acknowledgements
This work was supported financially by:
• The Programme Commission on Sustainable Energy and
Environment, The Danish Council for Strategic Research, via the
Strategic Electrochemistry Research Center (SERC) (www.serc.dk),
contract no. 2104-06-0011. (2006-2012)
• The Catalysis for Sustainable Energy (CASE) initiative funded by
the Danish Ministry of Science, Technology and Innovation.
• The 2nd generation alkaline electrolysis project, EUDP 63011-0200
• The Department of Energy Conversion and Storage, DTU
Thank you for your attention!
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