Alternative Energy Technologies:
Fuel Cells
Allan J. Jacobson
Center for Materials Chemistry
University of Houston
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Future Fuels and Electricity
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Now:
– Fossil fuels: natural gas, oil, coal
– Gas, steam turbines, combined cycle
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Intermediate:
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Hydrogen from fossil fuels
Fuel cells and new processes
Distributed systems
Superconducting transmission lines
Future
– Nuclear
– Solar
– Hydrogen from water
• Electrolysis
• Thermal from HT nuclear reactors
• Photo-electrolysis
– Renewables
– ‘Supergrid’
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Key Drivers
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Sources of Hydrogen
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What is a Fuel Cell?
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Fuel Cell Operation
500 – 1000 °C
porous cathode
electrolyte/membrane
Cathode, an anode, and an electrolyte
sandwiched between the two.
Oxygen from the air flows through the cathode
A fuel gas containing hydrogen, such as methane, flows past the anode.
Oxygen ions migrate through the electrolyte and react with the hydrogen to form water
Water reacts with the methane fuel to form carbon dioxide and hydrogen.
Electrons from the electrochemical reaction flow from anode to cathode through an external load
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Advantages of Fuel Cells
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High efficiency
Modular
Quiet
Non Polluting - no NOx
Distributed
Combined heat and power
Load flexible
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Fuel Cell History
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Fuel Cell History
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Fuel Cell Types I
Alkaline (AFC) developed for the
Apollo program
Polymer membrane (PEMC) leading
candidate for transportation
Phosphoric acid (PAFC) 200kW units
commercially available for combined
heat and power (CHP)
Molten carbonate (MCFC) and solid
oxide (SOFC) can work directly with
hydrocarbon fuels – 200+kW
demonstration units
Taken from B. C. H. Steele & A. Heinzel, Nature, 414 (2001) 345
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Fuel Cell Types II
Taken from B. C. H. Steele & A. Heinzel, Nature, 414 (2001) 345
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PEMFC
• Electrodes (anode and the cathode) separated by a polymer membrane electrolyte.
• Each of the electrodes is coated on one side with a thin platinum catalyst layer.
• The electrodes, catalyst and membrane form the membrane electrode assembly.
• Hydrogen and air are supplied on either side through channels formed in the flow field plates
Ballard® fuel cell
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Advanced Fuel Cell Electrodes-PEM
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% Anode = 0.35 mg/cm2 Pt Loading
% Anode = 0.72 mg/cm2 catalyst loading
140
1.0
120
0.8
100
80
0.6
60
0.4
40
0.2
20
0.0
0
50
100
150
200
250
300
350
400
450
500
550
Current Density (mA/cm2)
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0
600
Power Density, (mW/cm2)
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A current DOE target is to develop alternative
electrodes to replace the Pt and Pt-Ru electrodes that
are used as cathode and anode electrocatalysts in PEM
fuel cells.
Ideally the anode catalyst would be tolerant to CO and
S present in the hydrogen fuel.
The figure shows a new class of non-Pt electrocatalysts
that have activity comparable to Pt as shown by the
performance of cell with the new catalyst as the anode.
Voltage (V)
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SOFC
Cathode
Interconnection
Electrolyte
Anode
(La,Sr)MnO3
(La,Sr)CrO3
8%Y2O3-ZrO2
Ni/ 8%Y2O3-ZrO2
1.5 m extruded tubular (2.2 mm) porous cathode
plasma spraying (85 m)
thick-film (30–40 m)
porous layer (100 m) by a slurry-spray process
Siemens Westinghouse fuel cell
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Future Applications
Application
Size (kW)
Fuel cell
Power systems
for portable
electronic devices
0.001–0.05
PEMFC
DMFC
SOFC
hydrogen
methanol
methanol
Micro-Combined Heat
and Power
1–10
PEMFC
SOFC
LPG
Natural gas, LPG
Auxiliary power units
1–10
SOFC
LPG
Distributed Combined Heat 50–250
and Power
PEMFC
MCFC
SOFC
natural gas
natural gas
natural gas
City buses
200
PEMFC
hydrogen
Large power units
1000–10,000
SOFC/GT
natural gas
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Fuel
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Technical Challenges
Many Challenges in Materials and Materials Processing
– CO tolerant electrocatalysts
– Better membranes for PEMFC and DMFC
– Intermediate temperature high performance
electrodes
– Low cost fabrication processes for SOFC
– New materials!
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Core Technology Program Participants:
Gas Technology Institute – Des Plaines, IL
Georgia Tech Research – Atlanta, GA
Montana State University – Bozeman, MT
NexTech Materials, Ltd – Worthington, OH
Northwestern University – Evanston, IL
Southwest Research Institute – San Antonio, TX
Texas A&M University – College Station, TX
University of Florida – Gainesville, FL
University of Illinois – Chicago, IL
University of Houston – Houston, TX
University of Missouri – Rolla, MO
University of Pittsburgh – Pittsburgh, PA
University of Utah – Salt Lake City, UT
University of Washington – Seattle, WA
Virginia Tech – Blacksburg, VA
Current Industrial Teams
Argonne National Laboratory
Lawrence Berkeley National Laboratory
Los Alamos National Laboratory
National Energy Technology Laboratory
Oak Ridge National Laboratory
Pacific Northwest National Laboratory
Sandia National Laboratories
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Water Electrolysis
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Sources of Hydrogen
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Hydrogen Production
CO2
Sequestration
Membrane reactor
CO2 +H2
Water Gas
Shift Reactor
CO2
Hydrogen
Separation
Device
(PSA, HTM)
CO +H2
H2
Fuel Cells
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