Intermediate temperature and pressure electrochemical reactors

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

Fuel Cell & Hydrogen Technologies JP

SP2: Catalyst and Electrodes

Borovetz, Bulgaria

June 2nd and 3rd 2014

Christodoulos Chatzichristodoulou Technical University of Denmark, Department of Energy Conversion and Storage

EERA FCH2 SP2 Workshop

Outline

7/9/2014

• Motivation

• Electrolytes

• Cell concept

• Electrochemical testing equipment

• H2O electrolysis

• Summary

• Outlook


Motivation - Sustainability

7/9/2014

• 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)


Motivation – Process conditions

7/9/2014

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)


Motivation – Some facts

7/9/2014

• 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


Electrolytes – The Norby gap

7/9/2014

T. Norby, Solid State Ionics, 125 (1999) 1


Electrolytes – Possibilities

7/9/2014

• 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


Electrolytes – Immobilized KOH (aq.)

7/9/2014

F. Allebrod et al., Internat. J. Hydrogen Energy, 37 (2012) 16505


Cell concept

7/9/2014

Alkaline (KOH) electrolyte (water electrolysis):

OH-

e- e-

O2

O2

H2O

H2

Alkaline (KOH) electrolyte (water electrolysis):

OH-

e- e-

O2

O2

H2O

H2

OH-

e- e-

O2

O2

H2O

H2

• Aq. electrolyte immobilized in mesoporous ceramic matrix

• Gas diffusion electrodes

Aqueous KOH/K2CO3 electrolyte (co-electrolysis):

e- e-

CO2, H2O

HCO3-CO3

2-

CH3OH, CO2, H2O, …

CO2, O2, H2O

CO2, O2, H2O

Aqueous KOH/K2CO3 electrolyte (co-electrolysis):

e- e-

CO2, H2O

HCO3-CO3

2-


CO2, O2, H2O

CO2, O2, H2O

e- e-

CO2, H2O

HCO3-CO3

2-


CO2, O2, H2O

CO2, O2, H2O

e- e-

CO2, H2O

HCO3-CO3

2-


CO2, O2, H2O

CO2, O2, H2O

CO2

CO2

Ceramic powder, e.g.

SrTiO3, forming a

mesoporous matrix

H+

e- e-

H2O

O2, H2O

CO2

CH3OH, H2O, CO2, …

Proton conducting (solid acid) electrolyte:

H+

e- e-

H2O

O2, H2O

CO2


H+

e- e-

H2O

O2, H2O

CO2


Proton conducting (solid acid) electrolyte:


Electrochemical testing equipment – Intermediate temperature and pressure rigs

7/9/2014

C. Chatzichristodoulou et al., Rev. Sci. Instrum. 84 (2013) 054101-12.

On/off valve

Flow controller

Check valve

Magnetic valve, NC/NO

Gas detector

Pressure controlling valve

Pressure relief valve

50 °C sf transfer line

liquid transfer line

Catalytic burner

transfer line

3-way valve

270° valve

Pressure sensor

Electropneumatic transducer

Sample holder

Pressure reduction valve

MS Mass Spectrometer

150 °C transfer line

Manometer

NC

Needle valve

Electric signal

FL-14B

N2

O2

H2

CO2

Autoclave

20-300°C

1-100 bara

1-100 bara

20

3.2

mm

Ø63.5 mm

P1=70-100 bara 1bara

0

Ex

hau

st outsid

e 252

H2, CO,

CO2(g),

N2, O2,

H2O(g), NH3,

CH4

H2O(l),

CxHyOz(l)

MV-01

MV-02

MV-03A

MFC-01

MFC-02

MFC-03

MFC-04

C-03

C-04A

CB-01

G-01

G-02

G-03

PCV-14

FL-14A

MV-14

V-01C

C-02B

V-

01A

V-

02A

V-

03A

V-04A MV-04A

NC

Ou

tsid

e 2

52

Wall p

an

el

Inside GHC

~2 bara

air supply

PS-12

ET-13

H2

O2

CO

MS

P-01

P-02

P-03

P-04

V-01B

V-02B

NV-

03B

V-04B

NC

NC

NC

NC

V-

02C

R12

V-04D

V-

04

C

Ventilation

V-

03

C

MFC-05

C-01B

C-02A

C-01A

C-05

P-12

PRV-11

7/8”

1/8”

1/16”

1/8”

1/16”

1/8”

1/8”

1/8”

V-13

1 6 7 3 5

C-14

CB-14


H2O electrolysis - Performance

7/9/2014

Current density [A•cm-2]

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

240 °C

40bar

F. Allebrod et al., J. Power Sources 229 (2013) 22-31

H2 electrode: Inconnel foam based

Electrolyte: KOH (aq.)

O2 electrode: Ni foam based


H2O electrolysis - Performance

7/9/2014

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.


H2O electrolysis - Degradation

7/9/2014


H2O electrolysis - Upscaling

7/9/2014

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


Summary

7/9/2014

• 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


Outlook

7/9/2014

• 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


Acknowledgements

7/9/2014

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!

Intermediate temperature and pressure electrochemical reactors

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