Sulfur Tolerance of La0.3M0.7Fe0.7Cr0.3O3 -δ (M= Sr, Ca) Solid Oxide Fuel Cell Anodes
Previous and current studies in our group employing La0.3M0.7Fe0.7Cr0.3O3-δ (M= Sr, Ca) perovskite oxides as both the anode and cathode electrode material, screen printed onto both sides of a YSZ electrolyte with a Gd0.9Ce0.1O2-δ (GDC) buffer layer separating the electrodes and the YSZ, showed very good electrochemical performance in both H2 and CO/CO2 atmospheres in the absence of H2S [5-6]. Therefore, in this work, extensive electrochemical studies, focusing on the performance of La0.3M0.7Fe0.7Cr0.3O3-δ (M= Sr, Ca) in a symmetrical SOFC configuration and operating on H2 and/or CO/CO2 fuels containing varying concentrations of H2S (5- 30 ppm), were carried out at 500 - 800 oC. Also, the effect of the dc bias on the sulfur tolerance of these materials has been examined.
Our preliminary results have shown that La0.3Sr0.7Fe0.7Cr0.3O3-δ (LSFCr) electrodes, operated as an anode in humidified H2 plus up to 9 ppm H2S (balance in H2) at 800 oC showed no H2S poisoning. The polarization resistance (Rp) observed for the cell in 30% humidified H2 was 1.20 Ω.cm2 at 800 oC and, with the addition of 9 ppm H2S, there was no observed change in Rp. However, in dry CO/CO2, the addition of H2S showed a ca. 3% increase in Rp, but without any further degradation after longer term exposures to H2S. Importantly, when the H2S was removed from this gas mixture, the performance recovered fully.
Acknowledgements – We are very grateful to the SOFC Canada NSERC Strategic Research Network, as well as Carbon Management Canada, for the support of this work.
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