Electrochemical oxidation of sour natural gas over La0.4Ce0.6O1.8-La0.4Sr0.6TiO3 +/-delta anode in SOFC: A mechanism study of H2S effects

摘要

For solid oxide fuel cell with La0.4Ce0.6O1.8-La0.4Sr0.6TiO3 +/-delta (LDC-L4ST) impregnated anodes, the electrochemical oxidation rates of H-2 and CH4 were significantly improved when H2S (0.5%) was present in the feeds as evidenced by the substantially decreased polarization resistance and the improved power density of the cell although H2S did not predominantly function as a fuel. Conductivity measurements of various anode component materials implied that the addition of H2S into the feeds increased their conductivities. More importantly, from the mass spectroscopic analysis of the anode gas effluents and the thermodynamic calculations, direct evidences of H2S caused SOFC performance improvement have been confirmed, three distinct regions for the electrochemical oxidation pathways of 0.5% H2S-CH4 vs. over-potential (eta) were proposed to explain the effect. The chemisorbed S species, together with LDC-L4ST, behaved as an effective catalyst promoting CH4 oxidations via COS and CS2 intermediates. The addition of LDC in the anode enhanced this synergic effect and further increased CH4 electrochemical conversion as well as coking resistance in comparison of the L4ST anode. (C) 2015 Elsevier B.V. All rights reserved.