Single Cell Testing

Understanding of reactions and mechanisms that influence the performance, durability and degradation behavior of solid oxide fuel cells, SOFC’s, are of high importance for the development of the SOFC technology.

FCH Test Center offers single cell testing of SOFC’s following a wide range of protocols, including one or more of the following modules: performance test, degradation test, accelerated test as well as post mortem characterization. When detailed electrochemical testing is combined with analysis and microscopy it can show:

• The general performance level of  the cell
• The long-term degradation behavior / durability
• The part of the cell that has the greatest internal loss
• The part of the cell that causes the greatest degradation
• The integrity of the cell - identification of its weakest point

Performance Test

A “finger print” reveals the performance of the cell. The finger print combines testing of a SOFC single cell (Table 1) at a number of temperatures with several gas compositions. The finger print is performed at the beginning and at the end to allow for comparison.Nyquist Plot

Figure: Nyquist plot of electrochemical impedance spectroscopy, EIS, at different temperatures.

Above figure shows an example of how the impedance response can change when one test parameter is changed, in this case  temperature. Changing the conditions can reveal how much the different parts of a SOFC contribute to the total cell resistance (internal losses).

Durability / Degradation Tests

Durability and degradation tests can be performed in numerous ways, for example A: Long-term testing (+1000’s of hours, constant/variable conditions), B: Accelerated testing (harsh conditions such as: high load, high temperature, redox stability, thermal cycling ), C: Sensitivity towards gaseous impurities (e.g. addition of H2S to the inlet gas)
Below figure shows how we can monitor the long term degradation of a cell. Detailed EIS measurements can complement such a long term test [2].

Endurance plot

Figure: Left: Development of the cell voltage versus time for an SOFC measured at 750 °C and constant current for 1500 h. Right: Impedance measurements.

References

[1] T. Ramos, IMCC VI, 213th ECS Meeting, 2008
[2]A. Hagen, Y.L. Liu, R. Barfod, P.V. Hendriksen, J. Electrochem. Soc. 155(10) (2008) B1047-B1052.

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 Single Cell Testing brochure
Monitored parameters
Temperatures Center, corner & outlet
Gas flows Mass-flow controllers for each gas
Partial pressures pO2 (inlet), pO2 (outlet)
Cell coltage, current and in-plane voltage at both electrodes
Operating parameters
Temperature 650 - 1000 °C
Gas options H2, O2, CO, CO2, CH4, N2, Ar, H2S, H2O
Electrical Loads Up to 40 A (potentiostatic and galvanostatic testing)
Impedance At OCV or under current
Gas cleaning Removal of trace impurities from inlet gas (optional)
Influence of impurities Sensitivity towards sulphur and other
Table 1: Test conditions
http://www.fch.dk/services/single-cell-testing
20 JANUARY 2019