Coking Study in Anode Materials for SOFCs: Physicochemical Properties and Behavior of Mo-Containing Perovskites in CO and CH4 Fuels

Recent research trend on Solid Oxide Fuel Cells is aimed at utilizing non-hydrogen fuels [1-4]. When SOFC is running on syngas, methane and/or other hydrocarbons, on the typical Ni-YSZ anode carbon deposition occurs, which consequently significantly decreases SOFC cell performance, due to a decrease of the triple phase boundary catalytic sites, which are blocked by coking [1, 2]. Among candidate anode material for usage with such fuels, A₂MMoO_6-δ(A: Sr, Ba; M: 3d metals) ordered perovskites seem to be particularly interesting [3, 4]. However, the coking mechanism in such compounds is still under intensive research, due to a fact that carbon deposition process is affected with many factors, such as operation temperature, water content, etc. [1, 2].

In this study, B-site modified double perovskites with Sr₂Fe_1.5-xMn_xMo_0.5O₆ formula were investigated as candidate anode materials for SOFCs operating with syngas and/or methane, in terms of their crystal structure, oxygen nonstoichiometry, chemical stability, their electrochemical properties, and carbon deposition tolerance in CO and/or CH₄ gases. The coking effect on the electrical conductivity and SOFC performance was studied at different temperatures. Deposited carbon morphology, as well as degradation of microstructure of the materials were investigated by SEM. It was found that carbon deposition is significantly dependent on the operation temperature and annealing time. Elucidation of the coking mechanism on Sr₂Fe_1.5-xMn_xMo_0.5O₆-based anodes is given.

 

Acknowledgments

The project was funded by the National Science Centre Poland (NCN) on the basis of the decision number DEC-2011/03/N/ST5/04785.

One of the authors (K. Zheng) acknowledges financial support from the National Science Centre Poland (NCN) under the ETIUDA doctoral scholarship on the basis of the decision number DEC-2013/08/T/ST5/00100.

References

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4. K. Zheng, K. Świerczek, W. Zając, A. Klimkowicz, Solid State Ionics 257 (2014) 9-16.