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Fuel Cell Technology Status, Challenges, and Opportunities. Meilin Liu School of Materials Science &Engineering Georgia Institute of Technology Atlanta, GA 30332-0245 Presented to Electrical Energy Systems and Sustainability Workshop Georgia Tech November 29 – December 1, 2000. Outline.
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Fuel Cell TechnologyStatus, Challenges, and Opportunities • Meilin Liu • School of Materials Science &Engineering • Georgia Institute of Technology • Atlanta, GA 30332-0245 • Presented to • Electrical Energy Systems and • Sustainability Workshop • Georgia Tech • November 29 – December 1, 2000 Georgia Tech - SSI&EC
Outline • Introduction • Polymer Electrolyte Membrane Fuel Cells • Current technology • Applications: Portable/vehicle • Challenges/opportunities • Solid Oxide Fuel Cells (SOFCs) • Current technology • Applications:Stationary/distributed/EV • Challenges/opportunities • Concluding Remarks Georgia Tech - SSI&EC
Schematic of an individual fuel cell Load e’ Fuel in Oxidant in O2 H2 H+ H2 H2O Anion O2 H2O conductor Electrolyte (Ionic conductor) Depleted oxidant Depleted fuel Anode Cathode Georgia Tech - SSI&EC
Advantages of Fuel CellsOver conventional Technologies • High efficiency Internal combustion engine: <30% Fuel cell: 50% electrical, 85% overall (SOFC) • Environmental friendly Emits H2O or CO2 without pollutants Emits as much as 60% less CO2 than coal plant • Noise-free and no site restriction No mechanical friction or moving parts Georgia Tech - SSI&EC
PEMFCs: Challenges & Opportunities Efficient catalysts insensitive to impurities in the fuel such as CO; Efficient catalysts that promote a high rate of oxygen reduction; Alternative catalysts less expensive than Pt to reduce the cost. Georgia Tech - SSI&EC
End Plate Anode Electrolyte Cathode Bipolar Separator Repeating unit Anode A Planar Solid Oxide Fuel Cell Georgia Tech - SSI&EC
A Tubular Solid Oxide Fuel Cell Georgia Tech - SSI&EC
b 1m 4m Characteristics of GDC Powder by GNP Large surface area Compositional homogeneity Easy to densify 92% at 1250oC/5 hrs 95% at 1350oC/5 hrs Loose agglomerates Foam-like structure Fill density 0.059 g/cm3 120th of theoretical value Georgia Tech - SSI&EC
10m cathode GDC film electrolyte anode Substrate 30m ~8 m ~15 m Microstructures of Dry-Pressed Films Georgia Tech - SSI&EC
Porous SSC and 10 v%SDC Cathode A single cell cathode electrolyte 2m anode 30m Dense SDC Porous Ni-SDC Anode 2m 2m SOFCs Fabricated by Screen-Printing Georgia Tech - SSI&EC Changrong Xia, Fanglin Chen and Meilin Liu, Electrochemical and Solid State letters, 4(5) A52-A54 (2001).
Single cell performance of SDC-electrolyte SOFC Georgia Tech - SSI&EC
Significance of Interfacial Resistances Georgia Tech - SSI&EC
SOFCs: Challenges & Opportunities • New electrolytes with high ionic conductivities at low temperaturesinexpensive materials,longer life; • Nonstructural electrodes and interfaces to enhance performance, especially anodes for alternative fuels; • Cost-effective fabrication processes to dramatically reduce the cost; $4,000$400/KW; • Efficient catalysts insensitive to impurities in the fuel such as H2S. Georgia Tech - SSI&EC
Mesoporous Materials Meso-porous materials---porous inorganic solids with pore size 2-50nm Preparation -- surfactant templating mechanism Surfactant Inorganic precursor Remarkable properties: Narrow pore size distribution Pore size tunable (from 2nm to 50 nm) Large surface area (~1000 m2/g) Applications: Catalysis, selective separations, absorption medium, sensors, Electrodes for lithium batteries, fuel cells, and gas sensors. Georgia Tech - SSI&EC
Formation of Mesoporous SnO2 Tin chloride Cetyltrimethylammonium bromide Electrostatic interaction Aging Micelle formation S+I- interaction Calcining TEM image of SnO2 Georgia Tech - SSI&EC
Preparation of Mesoporous YSZ-NiO ( P E O ) ( P P O ) ( P E O ) m n m (Surfactant) Z r O C l + + N i C l YCl 2 2 3 (Inorganic species) -PEO -PPO Cl Cl R O H H O Y Cl Y 3 R Cl + R O YCl H Cl 2 H O 2 H O YCl + H O R 2 Georgia Tech - SSI&EC
TG-DSC, XRD of Mesoporous YSZ-NiO x o—YSZ x—NiO x x o o x o o o o Georgia Tech - SSI&EC
TEM and BET of Mesoporous YSZ-NiO 108 m2/g 4.5 nm TEM BET Georgia Tech - SSI&EC
500 nm Polystyrene Spheres Sr0.5Sm0.5CoO3 500 nm Micrographs of PS & Sr0.5Sm0.5CoO3 Georgia Tech - SSI&EC
Concluding Remarks • Fuel Cells are the most efficient/cleanest technology for conversion of chemical to electrical energy; • PEMFC and SOFC are the most versatile system for various applications; • Cost reduction is the key to successful commercialization of fuel cells; • Fuel cells will significantly influence our everyday life in the years to come. Georgia Tech - SSI&EC