1. MOLTEN CARBONATE FUEL CELLS ANSALDO FUEL CELLS: Experience & Experimental results
Filippo Parodi /Paolo Capobianco
(Ansaldo Fuel Cells S.p.A.)
Roma, 14th & 29th March 2007

2. MOLTEN CARBONATE FUEL CELLS ANSALDO FUEL CELLS EXPERIENCE
General Content
Working principles of Fuel Cells
MCFC technology
Key components and materials
Technological development
LAB level tests
Paolo Capobianco (Ansaldo Fuel Cells S.p.A.)
Roma, 29th March 2007

3. What is a Fuel Cell? How a Fuel Cell work? Fuel Cells
It is an electrochemical device that converts energy of a chemical reaction into electricity without any kind of combustion and with high conversion capability.
How a Fuel Cell work?
It operates like a Battery but it can continuously generate electricity as long as fuel (typically H2) and oxidant (Air) are fed to its electrodes.

4. Battery Fuel Cell Fuel Cells
A generic Battery operation is based on spontaneous Oxidation-Reduction chemical reaction (G 0), between two materials (f. e. Zn and Cu++)
Fuel Cell
Fuel cell is a specific kind of Battery based on spontaneous Oxidation-Reduction chemical reaction between two gases

5. Zn + Cu++  Zn++ + Cu + Heat
Fuel Cells
How a Battery works
Zn Cu++  Zn Cu + Heat e
The reaction transfers directly 2 electrons
from the Zn atom to the Cu ++ ion.
To exploit the “natural tendency” of the Zn atom to deliver
2 electrons to the Cu++ ion so to produce electrical energy,
it is necessary to force the 2 electrons to reach the Cu++
through the external circuit (no direct contact of Zn and Cu++.) e
Zn Cu++  Zn Cu + Heat

6. Fuel Cells
Key feature of any electrochemical generator is its suitability to provide the spontaneous oxidation-reduction reaction, but by maintaining separate the two reagents ( Zn and Cu++ in this example).
Electrons current (I) flows from Zn to Cu++ through an external circuit
When DG=0 => I=0 (you have to recharge Battery with an external generator)

7. Daniell Battery Fuel Cells Anodic Semireaction Zn  Zn++ + 2eEc
Anode - Zn
Cathode + Cu
Porous Septum
Electrolyte
Electrolyte e e
Zn  Zn++
Cu++  Cu
Zn++SO4---
Cu++SO4---
Anodic Semireaction
Zn  Zn++ + 2e
Cathodic Semireaction
Cu  Cu++ + 2e
Total reaction
Zn + Cu++  Zn Cu

8. How a Fuel Cell works H2 + 1/2O2  H2O + Heat H2 + 1/2O2  H2O + Heat
Fuel Cells
How a Fuel Cell works
H /2O2  H2O + Heat
The reaction transfers directly 2 electrons from H2 to O2. e
To exploit the “natural tendency” of the H2 atom to deliver
2 electrons to the O2 atom so to produce electrical energy, it is necessary to force the 2 electrons to reach O2 through the external circuit.
H /2O2  H2O + Heat e H2 O2

9. Fuel Cells
Key feature of Fuel Cell is its suitability to provide the spontaneous oxidation-reduction reaction, but by maintaining separate the two reagents ( usually H2 and O2).
Electrons current (I) flows from H2 to O2 through an external circuit
In Fuel Cell you can continuously fed gases (DG  0 => I  0)

10. Fuel Cells
The direct conversion of the chemical energy of the Fuel (H2) into electrical energy permits conversion efficiencies significantly higher than by using the conventional processes combustion based
Moreover, no combustion means low environmental emissions

11. Molten Carbonate Fuel Cell (MCFC)
H2+ ½ O2  H2O + heat + electrical current
ELECTROCHEMICAL REACTION
Anodic H2+ CO3-- CO2+ H2O + 2e-
Cathodic CO2 + ½ O2 + 2e-  CO3--
Operation Temperature T=650 °C

12. Key components and materials (MCFC)
(Electrolyte)
ACTIVE POROUS COMPONENTS

13. Key materials and components (MCFC)
Anode
Anode material is not directly involved in gas reaction: It is the catalyst of H2 oxidation reaction
Other requirements for Anode material are chemical (gas and electrolyte) and morphological (high surface area) stability and high electrical conductivity

14. Key materials and components (MCFC)
Cathode
Cathode material is not directly involved in gas reaction: It is the catalyst of O2 reduction reaction
Other requirements for Cathode material are chemical (gas and electrolyte) and morphological (high surface area) stability and high electrical conductivity

15. Key materials and components (MCFC)
Electrolyte
Electrolyte material is directly involved in gas reaction
Other requirements for Electrolyte material is low ionic resistance and high electronic resistance
MCFC electrolyte material is liquid
A porous layer (Matrix) is filled by Electrolyte
Matrix material must have high chemical stability (gas and Electrolyte)
Matrix filled by Electrolyte must avoid direct reaction between H2 and O2

16. Key materials and components (MCFC)
Anode: Nickel (Ni-Cr/Al)
Nickel is catalyst for H2 oxidation (no Platinum request: low cost, CO use)
Nickel has high chemical stability in MCFC Anode working condition
Nickel has high electrical conductivity
Nickel is suitable to produce high porosity/high surface area anode
Anode section SEM analysis. Pores size is suitable for gas diffusion and electrolyte storage

17. Key materials and components (MCFC)
Cathode: LixNi(1-x)O
Nickel Oxide is catalyst for O2 reduction
Nickel Oxide has good (no total) chemical stability in MCFC working condition
Litiated Nickel Oxide has “high” electrical conductivity
Nickel Oxide is suitable to produce high porosity/high surface area cathode (typical catalyst bimodal structure)
Cathode section SEM analysis. It is possible to see the bimodal structure: larger size pores for gas diffusion , lower size pores for electrolyte storage

18. Key materials and components (MCFC)
Electrolyte:Li2CO3/K2CO3
Liquid Li/K-Na carbonate is an electrolyte solution of Li+, K+ (or Na+), CO3--
Liquid Li/K-Na carbonate has low ionic resistance
Liquid Li/K-Na carbonate has high electronic resistance
Matrix layer is made by LiAlO2
Chemical stability of LiAlO2 is very high
Electronic resistance of LiAlO2 is very high
Matrix section OM analysis. It is possible to see very low size pores (sub-micron size) for electrolyte storage. Matrix must be totally filled by electrolyte to avoid direct reaction between H2 and O2)

19. Key materials and components (MCFC)
METALLIC COMPONENTS

20. Key materials and components (MCFC)
Current collector
Current collectors have to permit a good gas distribution in the electrodes (anode, cathode)
Main requirements for current collector material are chemical stability (gas and electrolyte), good electrical conductivity, good mechanical properties

21. Key materials and components (MCFC)
Separator plate
Separator plate have to separate each single cells of a stack
Main requirements for separator plate material are chemical stability (gas and electrolyte), good electrical conductivity in active area, good mechanical properties

22. Key materials and components (MCFC)
NO ACTIVE AREA
ACTIVE AREA
(cells current flow through)

23. Key materials and components (MCFC)
Anode current collector: Ni/AISI310S/Ni
Nickel has high chemical stability in MCFC anodic working condition
Nickel has low electrical resistivity
Mechanical properties of Nickel in MCFC working condition (650 °C) are very poor
Trilayer Ni/AISI310S/Ni is used to have good chemical stability and adeguate mechanical properties Ni
AISI310S Ni
ACC section OM analysis. It is possible to see AISI310S layer between Ni layers

24. Key materials and components (MCFC)
Separator plate AISI310S (Active area)
AISI310S has good chemical stability in MCFC anodic and cathodic working condition (no direct contact with electrolyte)
AISI310S has low electrical resistivity
AISI310S corrosion layer has low electrical resistivity
AISI310S
Sep.plate section OM analysis (active area). It is possible to see very thin corrosion layers

25. Key materials and components (MCFC)
Separator plate AISI310S (No active area)
AISI310S is protected by Al coating (direct contact with electrolyte)
In stack operation Al coating forms Allumina layers very stable in working conditions (gas and electrolyte)
AISI310S AI
Sep.plate section OM analysis.(no active area) It is possible Al coating layer

26. Key materials and components (MCFC)
End first session