Thesis for degree: Licentiate of Engineering

(2.1)
(2.2)
(2.3)
(2.4)
(2.5)
Equation (2.1) is the reduction of oxygen in the cathode. Equations (2.2) and (2.3) are the
electrochemical reactions at the anodic three phase boundary (TPB). TPB is the region where
the ionic, electronic and gas phases meet close to the electrolyte and the electrode interface.
Equation (2.4) is the steam reforming of methane, which needs to be carried out prior to the
electrochemical reactions, and is usually called catalytic steam reforming reaction. Carbon
monoxide can be oxidized as in equation (2.3) or react with water as in equation (2.5).
Equation (2.5) is often called water-gas shift reaction. Note that methane is not participating
in the electrochemical reactions at the anodic TPB. It is catalytically converted, within the
anode, into carbon monoxide and hydrogen, which are used as fuel in the electrochemical
reactions [5-7]. These reactions can be viewed in the schematic illustration of an SOFC in
Figure 2.1.
Figure 2.1: Schematic SOFC structure.
The configuration of an SOFC can be formed in different ways; electrolyte or electrode
supported cells, shaped in a planar or tubular manner, co or counter directional flow. An
electrolyte supported SOFC has thin anodes and cathodes (~50 m), and the thickness of the
electrolyte is more than 100 m. An electrolyte supported SOFC works preferably at
temperatures around 1000 °C. In an electrode-supported SOFC, either the anode or the
cathode is thick enough to serve as the supporting substrate for cell fabrication, normally
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