The document describes using solid oxide electrochemistry to produce synthetic hydrocarbon fuels from water and carbon dioxide. It discusses using solid oxide electrolysis cells to electrolyze water and carbon dioxide into hydrogen, carbon monoxide, and oxygen. The gases can then undergo further electrochemical and catalytic reactions to produce synthetic fuels like diesel. Configurations are proposed involving porous electrodes, solid electrolytes, and downstream catalysts to facilitate these reactions in a single system. Thermochemical and electrochemical processes are compared for producing hydrogen and synthesis gas as intermediates for fuel synthesis.

1. Electrochemistry and Synthetic Hydrocarbons
from Water and Carbon Dioxide
Glenn Rambach
Third Orbit Power Systems, Inc.
Sept. 2009

2. Basics
High-temperature solid oxide electrochemistry for:
1) Fuel cells
2) Electrolysis
Electrochemistry and Synthetic Hydrocarbons
from Water and Carbon Dioxide
Electrochemistry and Synthetic Hydrocarbons
from Water and Carbon Dioxide
Water + CO2 to Fuels Like Diesel Fuel

3. O2 + 4e
_
2O2
_
Porous
metal/ceramic cathodeDense, Solid
Electrolyte
(usually yttrium stabilized zirconia, YSZ)
Porous
metal/ceramic anode
H2O
and/or
CO2
H2 and/or CO
e-
External
Load
O2
Basic solid oxide fuel cell (SOFC) mechanism
and/or
Fuel
side
Air
side
Temperature:
600 - 1000C
H2 + O2
_
H2O + 2e
_
CO + O2
_
CO2 + 2e
_
O2
_
O2
_
O2
_
O2
_
All reactions are
reversible to permit
water and CO2
electrolysis from an
applied voltage.

4. e-
Applied voltage
2O2
_
O2 + 4e
_
Porous
metal/ceramic cathodeDense, Solid
Electrolyte
(usually yttrium stabilized zirconia, YSZ)
Porous
metal/ceramic anode
H2O
and/or
CO2
H2 and/or CO
O2
Basic solid oxide electrolysis cell (SOEC) mechanism
and/or
Fuel
side
Oxygen
side
Temperature:
600 - 1000C
H2O + 2e
_
H2 + O2
_
CO2 + 2e
_
CO + O2
_
O2
_
O2
_
O2
_
O2
_

5. How do the reactants and products transport?
Where do reactions take place?

6. Electrochemical removal of oxygen and selective catalyst choices can favor
efficient use of electrolyzed hydrogen in production of synthetic fuel.
Electrochemically selective removal of half the oxygen from CO2 reduces the
consumption of hydrogen by 33%, compared to the use of reverse water gas
shift reaction, in the production of synthetic hydrocarbon fuel.

7. Porous cathode
Dense electrolyte
Porous anodeThermo-catalyst/Electro-catalyst
Gaseous flow channel
Electrolysis
electrode-electrolyte assembly
Electrochemical removal of oxygen and selective catalyst choices can favor
efficient use of electrolyzed hydrogen in production of synthetic fuel.
Gaseous flow

8. e-
O2
_
O2
_
O2
_ O2
_
O2
_ O2
_
O2
_
O2
_
e
_
e
_
e
_
e
_
e
_
e
_
e
_
e
_
CO2
H2O CO
CO2 + 2e
_
 CO + O2-
H2O + 2e
_
 H2 + O2-
H2
2O2-  O2 + 4e
_ O2
H2
CO
To conventional
Fisher-Tropsch
liquid fuel production
2H2 + CO  CH2 + H2O
Lost hydrogen
Electrochemically removed oxygen
Electrochemical removal of oxygen and selective catalyst choices can favor
efficient use of electrolyzed hydrogen in production of synthetic fuel.

9. Electrochemically selective removal of all oxygen from CO2 reduces the
consumption of hydrogen by 66%, compared to the use of reverse water gas
shift reaction and Fisher-Tropsch reaction 1, in the production of synfuel.
Electrochemical removal of oxygen and selective catalyst choices can favor
efficient use of electrolyzed hydrogen in production of synthetic fuel.
Electrochemical removal of oxygen and selective catalyst choices can favor
efficient use of electrolyzed hydrogen in production of synthetic fuel.

10. e-
O2
_
O2
_
O2
_ O2
_
O2
_ O2
_
O2
_
O2
_
e
_
e
_
e
_
e
_
e
_
e
_
e
_
e
_
CO2
H2O
CO2 + 2e
_
 CO + O2-
CO* + ½H2 + 2e
_
 CH + O2-
CH + ½H2  –CH2–
H2O + 2e
_
 H2 + O2-
2O2-  O2 + 4e
_ O2
[CH2]n
No lost
hydrogen
Electrochemically removed oxygen
Electrochemical removal of oxygen and selective catalyst choices can favor
efficient use of electrolyzed hydrogen in production of synthetic fuel.
COH2

11. e-
O2
_
O2
_
O2
_ O2
_
O2
_ O2
_
O2
_
O2
_
e
_
e
_
e
_
e
_
e
_
e
_
e
_
e
_
These and similar reactions may take place far
downstream, at lower temperature and with different catalyst.
CO2
H2O
CO2 + 2e
_
 CO + O2-
CO* + ½H2 + 2e
_
 CH + O2-
CH + ½H2  –CH2–
H2O + 2e
_
 H2 + O2-
2O2-  O2 + 4e
_ O2
[CH2]n
No lost
hydrogen
Electrochemical removal of oxygen and selective catalyst choices can favor
efficient use of electrolyzed hydrogen in production of synthetic fuel.
COH2

12. How do the flow channels, electrochemical
surface and down stream catalysts look in
a typical configuration?

13. Synfuel from CO2 and H2O using electrochemistry

14. Synfuel from CO2 and H2O using electrochemistry
Porous
Cathode Porous
Anode
Solid YSZ
Electrolyte
e-
H2O
and
CO2

15. Synfuel from CO2 and H2O using electrochemistry
Porous
Cathode Porous
Anode
Solid YSZ
Electrolyte
e-
H2O
and
CO2
Catalyst

16. Synfuel from CO2 and H2O using electrochemistry
Porous
Cathode Porous
Anode
Solid YSZ
Electrolyte
e-
H2O
and
CO2
H2O
CO2
Catalyst

17. Synfuel from CO2 and H2O using electrochemistry
Porous
Cathode Porous
Anode
Solid YSZ
Electrolyte
e-
H2O
and
CO2
H2O
CO2
Catalyst
O2
_
O2
_
O2
_
O2
_
O2
_

18. O2
Synfuel from CO2 and H2O using electrochemistry
Porous
Cathode Porous
Anode
Solid YSZ
Electrolyte
e-
H2O
and
CO2
H2O
CO2
Catalyst
O2
_
O2
_
O2
_
O2
_
O2
_
2O2
_
O2 + 2e
_

19. O2
Synfuel from CO2 and H2O using electrochemistry
Porous
Cathode Porous
Anode
Solid YSZ
Electrolyte
e-
H2O
and
CO2
H2O
CO2
Catalyst
CO
O2
_
O2
_
O2
_
O2
_
O2
_
H2
2O2
_
O2 + 2e
_

20. O2
CnH2n+2
(Synfuel)
Synfuel from CO2 and H2O using electrochemistry
Porous
Cathode Porous
Anode
Solid YSZ
Electrolyte
O2
_
O2
_
O2
_
O2
_
O2
_
e-
H2O
and
CO2
H2O
CO2
Catalyst
2O2
_
O2 + 2e
_
H2
CO

21. Synfuel from CO2 and H2O using electrochemistry
O2
CnH2n+2
(Synfuel)
Porous
Cathode Porous
Anode
Solid YSZ
Electrolyte
O2
_
O2
_
O2
_
O2
_
O2
_
e-
H2O
and
CO2
H2O
CO2
Catalyst
2O2
_
O2 + 2e
_
H2
CO
Triple
Region
H
O=
e-
e-O
H
H
Electrocatalyst
Cathode
H O=

22. Synfuel from CO2 and H2O using electrochemistry
CnH2n+2
(Synfuel)
Catalyst
O2
CnH2n+2
(Synfuel)
Porous
Cathode Porous
Anode
Solid YSZ
Electrolyte
O2
_
O2
_
O2
_
O2
_
O2
_
e-
H2O
and
CO2
H2O
CO2
Catalyst
2O2
_
O2 + 2e
_
H2
CO
n[CO2 + 2e
_
CO + O2
_
]
n[H2O + 2e
_
H2 + O2
_
]
Triple
Region
H
O=
e-
e-O
H
H
Electrocatalyst
Cathode
H O=

23. Synfuel from CO2 and H2O using electrochemistry
Temperature: 600 - 1000C
(Riso uses 650C for
2H2O + CO2  CH4 + 2O2)
CnH2n+2
(Synfuel)
Catalyst
O2
CnH2n+2
(Synfuel)
Porous
Cathode Porous
Anode
Solid YSZ
Electrolyte
O2
_
O2
_
O2
_
O2
_
O2
_
e-
H2O
and
CO2
H2O
CO2
Catalyst
2O2
_
O2 + 2e
_
H2
CO
n[CO2 + 2e
_
CO + O2
_
]
n[H2O + 2e
_
H2 + O2
_
]
Triple
Region
H
O=
e-
e-O
H
H
Electrocatalyst
Cathode
H O=

24. What configurations with high-temperature
power sources are possible?
How would they compare with synthetic
hydrocarbon production using high-temperature
thermochemical H2 from water, and reverse
WGS CO from CO2?

25. 3(H2O)
S-I
Thermochemical
CO2
Reverse
WGS
Fischer-Tropsch 1
-CH2-
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
25H2 + 8CO2  C8H18 + 16H2O
1.2 GJ of H2 to produce 1.0 GJ synfuel
S-I to Hydrogen, WGS to CO,
F-T to Synfuel
Heat
1
CO
and
H2
6 H atoms
2 H atoms

26. 3(H2O)
S-I
Thermochemical
Heat
CO2
Reverse
WGS
Fischer-Tropsch 1
-CH2-
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
25H2 + 8CO2  C8H18 + 16H2O
1.2 GJ of H2 to produce 1.0 GJ synfuel
Fischer-Tropsch 1
-CH2-
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
17H2 + 8CO2  C8H18 + 8H2O
0.82 GJ of H2 to produce 1.0 GJ synfuel
2(H2O) CO2
Elec
Electrolysis of
H2O and CO2
S-I to Hydrogen, WGS to CO,
F-T to Synfuel
Electrolysis to Hydrogen and CO,
F-T to Synfuel
Heat
1 2
CO
and
H2
CO
and
H2
6 H atoms 4 H atoms 2 H atoms
2 H atoms2 H atoms

27. 3(H2O)
S-I
Thermochemical
Heat
CO2
Reverse
WGS
Fischer-Tropsch 1
-CH2-
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
25H2 + 8CO2  C8H18 + 16H2O
1.2 GJ of H2 to produce 1.0 GJ synfuel
Fischer-Tropsch 1
-CH2-
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
17H2 + 8CO2  C8H18 + 8H2O
0.82 GJ of H2 to produce 1.0 GJ synfuel
2(H2O) CO2
Elec
Electrolysis of
H2O and CO2
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
9H2 + 8CO2  C8H18
0.43 GJ of H2 to produce 1.0 GJ synfuel
Elec
S-I to Hydrogen, WGS to CO,
F-T to Synfuel
Electrolysis to Hydrogen and CO,
F-T to Synfuel
Electrolysis to Hydrogen and CO,
F-T Polymerization to Synfuel
Heat Heat
1 2 3
CO
and
H2
CO
and
H2
Electrolysis of
H2O, CO2
and electro-
thermo-catalysis
of CO
6 H atoms 4 H atoms 2 H atoms
2 H atoms2 H atoms
2 H atoms -CH2-
H2O CO2

28. 2 H atoms3(H2O)
S-I
Thermochemical
Heat
CO2
Reverse
WGS
Fischer-Tropsch 1
-CH2-
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
25H2 + 8CO2  C8H18 + 16H2O
1.2 GJ of H2 to produce 1.0 GJ synfuel
Fischer-Tropsch 1
-CH2-
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
17H2 + 8CO2  C8H18 + 8H2O
0.82 GJ of H2 to produce 1.0 GJ synfuel
2(H2O) CO2
Elec
Electrolysis of
H2O and CO2
S-I to Hydrogen, WGS to CO,
F-T to Synfuel
Electrolysis to Hydrogen and CO,
F-T to Synfuel
Electrolysis to Hydrogen and CO,
F-T Polymerization to Synfuel
Heat
1 2 3
CO
and
H2
CO
and
H2
6 H atoms 4 H atoms
2 H atoms2 H atoms
3(H2O)
S-I
Thermochemical
CO2
Reverse
WGS
Fischer-Tropsch 1
-CH2-
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
25H2 + 8CO2  C8H18 + 16H2O
1.2 GJ of H2 to produce 1.0 GJ synfuel
Heat
CO
and
H2
6 H atoms
2 H atoms
3(H2O)
S-I
Thermochemical
H2
CO2
Reverse
WGS
CO
Fischer-Tropsch 1
-CH2-
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
25H2 + 8CO2  C8H18 + 16H2O
1.2 GJ of H2 to produce 1.0 GJ synfuel
O2
3
2
H2O
H2O
Heat
2H2
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
9H2 + 8CO2  C8H18
0.43 GJ of H2 to produce 1.0 GJ synfuel
Elec
Heat
Electrolysis of
H2O, CO2
and electro-
thermo-catalysis
of CO
-CH2-
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
9H2 + 8CO2  C8H18
0.43 GJ of H2 to produce 1.0 GJ synfuel
-CH2-
H2O CO2
2 H atoms

29. 2 H atoms3(H2O)
S-I
Thermochemical
Heat
CO2
Reverse
WGS
Fischer-Tropsch 1
-CH2-
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
25H2 + 8CO2  C8H18 + 16H2O
1.2 GJ of H2 to produce 1.0 GJ synfuel
Fischer-Tropsch 1
-CH2-
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
17H2 + 8CO2  C8H18 + 8H2O
0.82 GJ of H2 to produce 1.0 GJ synfuel
2(H2O) CO2
Elec
Electrolysis of
H2O and CO2
S-I to Hydrogen, WGS to CO,
F-T to Synfuel
Electrolysis to Hydrogen and CO,
F-T to Synfuel
Electrolysis to Hydrogen and CO,
F-T Polymerization to Synfuel
Heat
1 2 3
CO
and
H2
CO
and
H2
6 H atoms 4 H atoms
2 H atoms2 H atoms
3(H2O)
S-I
Thermochemical
CO2
Reverse
WGS
Fischer-Tropsch 1
-CH2-
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
25H2 + 8CO2  C8H18 + 16H2O
1.2 GJ of H2 to produce 1.0 GJ synfuel
Heat
CO
and
H2
6 H atoms
2 H atoms
3(H2O)
S-I
Thermochemical
H2
CO2
Reverse
WGS
CO
Fischer-Tropsch 1
-CH2-
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
25H2 + 8CO2  C8H18 + 16H2O
1.2 GJ of H2 to produce 1.0 GJ synfuel
O2
3
2
H2O
H2O
Heat
2H2
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
9H2 + 8CO2  C8H18
0.43 GJ of H2 to produce 1.0 GJ synfuel
Elec
Heat
Electrolysis of
H2O, CO2
and electro-
thermo-catalysis
of CO
-CH2-
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
9H2 + 8CO2  C8H18
0.43 GJ of H2 to produce 1.0 GJ synfuel
-CH2-
H2O CO2
2 H atoms
Heat
Fischer-Tropsch 1
-CH2-
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
17H2 + 8CO2  C8H18 + 8H2O
0.82 GJ of H2 to produce 1.0 GJ synfuel
2(H2O) CO2
Elec
Electrolysis of
H2O and CO2
CO
and
H2
4 H atoms
2 H atoms
Heat
Fischer-Tropsch 1
-CH2-
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
17H2 + 8CO2  C8H18 + 8H2O
0.82 GJ of H2 to produce 1.0 GJ synfuel
2O O
2(H2O) CO2
COH2
Elec
Electrolysis
membranes
2H2 CO
O2
3
2
H2O

30. 2 H atoms3(H2O)
S-I
Thermochemical
Heat
CO2
Reverse
WGS
Fischer-Tropsch 1
-CH2-
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
25H2 + 8CO2  C8H18 + 16H2O
1.2 GJ of H2 to produce 1.0 GJ synfuel
Fischer-Tropsch 1
-CH2-
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
17H2 + 8CO2  C8H18 + 8H2O
0.82 GJ of H2 to produce 1.0 GJ synfuel
2(H2O) CO2
Elec
Electrolysis of
H2O and CO2
S-I to Hydrogen, WGS to CO,
F-T to Synfuel
Electrolysis to Hydrogen and CO,
F-T to Synfuel
Electrolysis to Hydrogen and CO,
F-T Polymerization to Synfuel
Heat
1 2 3
CO
and
H2
CO
and
H2
6 H atoms 4 H atoms
2 H atoms2 H atoms
Heat
Fischer-Tropsch 1
-CH2-
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
17H2 + 8CO2  C8H18 + 8H2O
0.82 GJ of H2 to produce 1.0 GJ synfuel
2(H2O) CO2
Elec
Electrolysis of
H2O and CO2
CO
and
H2
4 H atoms
2 H atoms
Heat
Fischer-Tropsch 1
-CH2-
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
17H2 + 8CO2  C8H18 + 8H2O
0.82 GJ of H2 to produce 1.0 GJ synfuel
2O O
2(H2O) CO2
COH2
Elec
Electrolysis
membranes
2H2 CO
O2
3
2
H2O
3(H2O)
S-I
Thermochemical
CO2
Reverse
WGS
Fischer-Tropsch 1
-CH2-
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
25H2 + 8CO2  C8H18 + 16H2O
1.2 GJ of H2 to produce 1.0 GJ synfuel
Heat
CO
and
H2
6 H atoms
2 H atoms
3(H2O)
S-I
Thermochemical
H2
CO2
Reverse
WGS
CO
Fischer-Tropsch 1
-CH2-
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
25H2 + 8CO2  C8H18 + 16H2O
1.2 GJ of H2 to produce 1.0 GJ synfuel
O2
3
2
H2O
H2O
Heat
2H2
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
9H2 + 8CO2  C8H18
0.43 GJ of H2 to produce 1.0 GJ synfuel
Elec
Heat
Electrolysis of
H2O, CO2
and electro-
thermo-catalysis
of CO
-CH2-
Fischer-Tropsch 2
CH2 + CH2 + . . . + CH2 + H2
CnH2n+2 (synfuel)
For Octane:
9H2 + 8CO2  C8H18
0.43 GJ of H2 to produce 1.0 GJ synfuel
-CH2-
H2O CO2
2 H atoms
O2
3
2
O
H2
O
CO
O
CH
CH2
Electrolysis
membrane

31. What do the electrolysis an electrocatalytic reactions
look like?
What are the possible steric effects that may help
define the specific catalytic formulations that can
permit reduction of CO in the presence of hydrogen?

32. O2
_Solid oxide
electrolyte
O2
_
O2
_O2
_
O2
_
O-C-O
C-O
O
H H H-C-H
Cathode
Catalyst
Out
C-H
e-
Porous cathode
Gas in
O-C-O*
C-O*
C-H
Cathode
Catalyste
_
e
_
e
_
O2
_
A-B* = metastable state of A-B
CO2 + 2e-  CO + O2- +2e- + nXHm  CHn.m +nX + 2O2-
Cathode Cathode
Electrocatalysis
e- e-
H2O + + 2e-  2H + O2-
Cathode
e-
O2
X = C or O or H
Possible electro-catalytic and thermo-catalytic sterics, metastable states and reaction
schemes. This is where the research lies for electrochemical replacement of both
reverse water gas shift and the Fisher-Tropsch reactions thermochemistry.

33. Solid Oxide Fuel Cell Examples

34. Ceramatec solid oxide fuel cell/electrolyser
Planar cells

35. 120 kWe tubular solid oxide fuel cell. The system design can essentially be the same for a synthetic
hydrocarbon production system reversing the electrochemical process.
Courtesy: Siemens Westinghouse