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Hochtemperatur-Brennstoffzellen

Solid oxide fuel cells

Due to their potential for power generation in stationary and transport applications, fuel cells are attracting great interest. Solid Oxide Fuel Cells (SOFCs) contain a dense oxygen-ion conducting ceramic as electrolyte. The electrolyte is embedded between a porous anode layer composed of a ceramic-metal composite at the fuel side of the cell and a nanoporous oxygen-ion and electronic conducting ceramic cathode layer at the oxidant side of the cell. SOFC operate at temperatures in the range of 700-1000 °C and are expected to achieve net electrical efficiencies up to 65% at reduced pollutant emission for electrical power generation in the 1 kW to 10 MW range.

Working Principle:

 

In a fuel cell the chemical redox reaction of any fuel (hydrogen, gas) with air is separated into two partial reactions by a gas-tight, O2--conducting electrolyte as depicted in the figure. The dissociation of oxygen molecules and the reduction of oxygen atoms take place in the porous cathode while the fuel is oxidized in the porous anode as. Applying an electrical load, oxygen ions propagate through the O2--conducting electrolyte ceramic from the cathode to the anode. Due to the difference in chemical potentials between the cathode and anode a cell voltage in the order of 1 V is generated. To realize a useful power output, a large number of relatively small single cells are connected in parallel and in series using ceramic or metallic interconnects.

The decisive factors for SOFC systems are the efficiency of single cells and the lifetime of the components. The research at LEM in the field of SOFC materials focuses on both, the chemical and microstructural characterization of new materials as well as investigation of degradation processes of commonly used materials. The research includes all parts of the SOFC: cathode, electrolyte and anode.

1) Cathode

§    Nanocrystalline mixed ionic electronic conducting thin film cathodes

2) Electrolyte

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3) Anode
§     Ni model anodes

§     Ni cermet anodes