Materials Issues in Alkaline Fuel Cells Analytic Energy ...
Transcript of Materials Issues in Alkaline Fuel Cells Analytic Energy ...
![Page 1: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/1.jpg)
© ChevronTexaco 2002 Business UnitDOC ID
Materials Issues in
Alkaline Fuel Cells Analytic Energy Systems, LLC
D.Bloomfield
4/23/03
![Page 2: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/2.jpg)
2Business UnitDOC ID
Introduction
•Performance•Carbonates•Concentration Polarization•Circulating Electrolyte•Material Degradation•Monopolar Cells•Conclusions •Recommendations
![Page 3: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/3.jpg)
3Business UnitDOC ID
AFC (5cell) Substack Performance (circa 1969)Precious Metal 20 mg/cm2 Cathode 10 mg/cm2 Anode
![Page 4: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/4.jpg)
4Business UnitDOC ID
Companies that Left AFCGulzow, Journal of Power Sources, 61 (1996) 99-104
Allis Chalmers 1959
UTC – Apollo, LEM, Commercial PC10, Military PC3, Shuttle – Left 1970’s
Terminated - Siemens, Varta (1993), GH (1994),
ISET (1994), DLR (1994), ELENCO(1995),
Hoechst, Zetek (2002)
Examine Old Conclusions in Light of New TechnologyWhere is the New Technology?
![Page 5: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/5.jpg)
5Business UnitDOC ID
Relative Fuel Cells PerformanceVarying Operating Conditions
Comparative PerformanceSOFC, PEM, AlkFC
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
10 100 1000 10000
Current Density amp/cm2
Cel
l vol
ts
Delphi CFCLGlobalTESOFCoAnalyticAFC3GMP&WKordeschAFC 2
![Page 6: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/6.jpg)
6Business UnitDOC ID
AlkFC ChemistryMolten Alkali (300C) & Aqueous Alkali (120C)
![Page 7: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/7.jpg)
7Business UnitDOC ID
Trapped vs Circulating electrolyteCirculating Electrolyte
Problems• Thick Films Offsets High Ionic Conductivity
• Pressure Drop Along Cell Matrix Contributes to Flooding
• Electrolyte Flow Maldistribution
— Contributes to Carbonate Problems— Concentration Polarization
Advantage• Permits draining electrolyte to limit corrosion
• Electrolyte Serves as Coolant
![Page 8: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/8.jpg)
8Business UnitDOC ID
Effect of Carbon Dioxide
![Page 9: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/9.jpg)
9Business UnitDOC ID
Controlling Electrolyte Distribution Within Trapped Matrix
Deviations from the optimum fill volume leads to significant performance losses
Carbonate alters Density and saturation Properties
![Page 10: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/10.jpg)
10Business UnitDOC ID
Concentration PolarizationBigger Effect Than Resistance Pourbaix
![Page 11: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/11.jpg)
11Business UnitDOC ID
Circulating Electrolyte Modeling Flow Maldistribution and Concentration Gradients
Flow Distribution Concentration Distribution
![Page 12: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/12.jpg)
12Business UnitDOC ID
Material Degradation
Carbon Corrosion
Catalyzed by precious metal
Catalyst Corrosion
Nickel Powder, Raney Ni /Particulate/Cu 9
Plastic Decomposition
Teflon
Cell Frame Materials
Ceramics (electrolyte matrix)
![Page 13: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/13.jpg)
13Business UnitDOC ID
Effect of KOH on Supported Pt CatalystTomantschger, Findlay, Hanson, Kordesch, Srinivasan.-Journal of Power Sources, 29 (1990) 443 - 450
•KOH exposure to platinum supported carbon catalyst drastically affects noble metal.
•Platinum particles Agglomeration starts with exposure to KOH
• Agglomerates size increased logarithmically over 48 h.
•Particle size increased from <50 to over 200 microns
Has Anyone Tried Non-Carbonaceous Support ?– Carbides– Borides
![Page 14: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/14.jpg)
14Business UnitDOC ID
Carbon CorrosionTomantschger, Findlay, Hanson, Kordesch, Srinivasan.-Journal of Power
Sources, 29 (1990) 443 - 450
•Pt (1 mg/g carbon) increases corrosion rate in first 50 h
•Corrosion levels off in first 200 h (outer surface is wetted).
•Rapid increase in the corrosion rate after 500 h•Electrolyte penetrates and corrodes inside of the
carbon agglomerates
Observations confirm noble metal acts as a carbon corrosion catalyst.
![Page 15: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/15.jpg)
15Business UnitDOC ID
Nickel Alternatives - Cathode Catalyst CorrosionSinger & Fielder Journal of Power Sources, 29 (1990) 443 - 450
Corrosion test screening of alkaline fuel cell oxygen reduction electrode candidates
Pyrochlore (Pb2Ru206.5 )
Short Term Stability
Long Term Stability Questions
Spinel NiCo204
Unstable
Comparisons made with long term performance tests
Catalysts Should be tested for Peroxide Decomposition
![Page 16: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/16.jpg)
16Business UnitDOC ID
Anode Instability& CorrosionE. Gulzow, M. Schulze, G. Steinhilber Journal of Power Sources 4656 (2002) 1–10
Nickel/TFE/Copper Variations Tried
Anode Problems Due More To TFE Instability
Than Catalyst Activity
– Resistance & Concentration Polarization (Carbonation)
– Loss of Hydrophobicity (TFE instability)
– Capillary Structure (carbonation )
– Flooding (Teflon instability)
![Page 17: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/17.jpg)
17Business UnitDOC ID
Peroxide Mechanism & Cathode Reaction
Pt is Good Peroxide Decomposition Catalyst
Pt Catalyzes the Oxidation of Carbon Support
Ni is Not a Good Decomposition Catalyst
Cathode Mechanism
Chantenet et al JES 150 (3) D47-D55 (2003)
![Page 18: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/18.jpg)
18Business UnitDOC ID
Peroxide ConcentrationPourbaix
Peroxide Ion [HO2- ] vs Potential & PO2
@pH 14
1.E-07
1.E-05
1.E-03
1.E-01
1.E+01
1.E+03
1.E+05
1.E+07
-1.00 -0.80 -0.60 -0.40 -0.20 0.00 0.20
Potential - volts
Pero
xide
Ion
[atm
]
1.E-051.E-061.E-071.E-08
![Page 19: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/19.jpg)
19Business UnitDOC ID
PTFE Physical & Chemical StabilityTomantschger, Findlay, Hanson, Kordesch, Srinivasan.-Journal of Power Sources, 29 (1990) 443 - 450
•KOH exposure alters surface properties of PTFE— Decreased contact angle— Surface energy
•PTFE SEM Surface Examination — Roughening Caused by KOH Electrolyte.— Function of PTFE Types and Particle Sizes
•PTFE Changes Under Fuel Cell Operating Conditions Contributes to Electrode Degradation,
•PTFE Chemical Degradation — Caused by Electrolyte Access — Accelerated by Peroxide Presence
![Page 20: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/20.jpg)
20Business UnitDOC ID
Materials Properties Variation Summary
Physical Properties WettabilitySurface TensionViscosityConductivityWater Saturation Properties
Chemical ReactivityCarbonate formation
ReactantsCell materials (Frames)
How many problems are Peroxide Related?
![Page 21: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/21.jpg)
21Business UnitDOC ID
Monopolar vs Bipolar Design
Monpolar Design
•Resistivity ΦΩ (resistance loss)=f(x2) x=conduction path
•Poor catalyst utilization•Cell Stiffness Tenting & Structure•Follow up Systems•High Part Count
![Page 22: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/22.jpg)
22Business UnitDOC ID
DesignMonopolar vs Bipolar
![Page 23: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/23.jpg)
23Business UnitDOC ID
Monopolar Current Collection Effect of Resistance in Electrode Plane
![Page 24: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/24.jpg)
24Business UnitDOC ID
Conclusions
Alkaline Fuel Cell ChallengeMany Symptoms Linked to Peroxide Effects
Good Peroxide Decomposition Catalysts are
Poor Reduction Catalyst or Corrosion Catalysts
Circulating Electrolyte is used because
Catalyst Corrodes in Presence of Electrolyte
Carbonate Formation
Monpolar Design is bulky and has poor catalyst utilization
![Page 25: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/25.jpg)
25Business UnitDOC ID
Directions for Alkaline Fuel CellMaterial Development
Performance/LifeRun Full Cells for Performance & Durability
Half Cells don’t have the Same Problems
Materials Degradation Forced Design CompromisePTFE Electrocatalysts
Carbon Cell Frame
Matrix Electrolyte
DesignBipolar Cells Trapped Electrolyte
![Page 26: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/26.jpg)
26Business UnitDOC ID
Competition From SOFC
![Page 27: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/27.jpg)
27Business UnitDOC ID
Competition from PEM
![Page 28: Materials Issues in Alkaline Fuel Cells Analytic Energy ...](https://reader036.fdocuments.net/reader036/viewer/2022081505/62a3426e6282bd22e2096f8d/html5/thumbnails/28.jpg)
28Business UnitDOC ID
Internal Combustion Engines Run on H2
Honda Scooter & ECD Hydride Storage