One of the impediments to the implementation of SOFCs is their degradation in the presence of impurities in the fuel. Phosphine (PH3) is present in coal syngas at ppm levels, and a number of experiments have shown that the nickel anode is damaged by long term exposure to ppm levels of phosphine in various fuels. Because phosphine is exposed to high temperatures (~800�C) and varying amounts of water and oxygen in fuels, the exact nature of the phosphorus species reaching the anode is unknown. Thermodynamic calculations vary in the predicted species at equilibrium, some of which are HPO (mass 48), HPO2 (mass 64), HPO3 (mass 80), and P4O10 (mass 288). We report mass spectroscopic analyses of exhaust gases from SOFC test systems, with and without Ni/YSZ anodes in the path of the gas flow. The mass spectrometer, a MKS Cirrus system, has a mass range of 1 � 100 amu and a detection limit of ~0.001 torr. In dry hydrogen (<1 torr H2O), phosphine survives exposure to 800�C, but reacts at lower temperatures. In wet hydrogen (10 torr H2O), or in the presence of Ni/YSZ, the phosphine signal disappears. No new mass signals appear in all conditions, suggesting that phosphine reaction products have a mass outside the 100 amu range of the mass spectrometer.

Mass spectroscopic analysis of anode exhaust gases from a SOFC

247th National Meeting (2014)

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