| Mixed ionic and electronic conducting La1-xSrxMn 1-yCryO3+delta (LSMC) oxides, both single phase and GDC or YSZ composites were studied as anodes in humidified fuels at 700 and 800°C. Their electronic conductivity, oxygen non-stoichiometry, redox stability, and chemical stability in H2, with and without 10 and 30 ppm H2S, were determined. The catalytic activity of single phase LSMC oxides towards the H2 oxidation reaction was examined as a function of Sr and Cr content. In humidified H2, La0.9Sr 0.1Mn0.6Cr0.4O3+delta anodes showed the best electrochemical performance. The benefits of not doping with Sr were confirmed for single phase and GDC composite LaMn0.5Cr0.5 O3+delta anodes. These composites exhibited non-coking behaviour in 60:40 CH4:CO2 under polarization. In 10 and 30 ppm H2S, La0.9Sr0.1Mn0.6Cr 0.4O3+delta- and La0.8Sr0.2Mn 0.4Cr0.6O3+delta-YSZ composites showed no change in resistance at open-circuit, but lost performance (4-16%) at 0.6 V. No evidence of surface sulphur species was observed, consistent with rapid and complete recovery of composite anodes from sulphur poisoning. |
