Preparation And Performance Of Perovskite Sulfur Tolerant Anode For Solid Oxide Fuel Cells

The application of solid oxide fuel cell is limited due to higher operating temperatures, carbon deposition, sulfur poisoning and so on. As a result, it is important to develop the novel sulfur-resistant anode. Based on doping elements and fabricating composite electrodes, the perovskite-type anode was made. The electrochemical performance and sulfur tolerance were evaluated.In our work, the Y0.9Sr0.1Cr0.5Mn0.5O3-δ (YSCM) material was synthesized by the EDTA-citric method. In addition, the sulfur-resistance and electrochemical performance were also tested. The prepared powders were calcined at 1000℃,1100℃,1200℃ and 1300℃, respectively. The single perovskite strcture can be observed after calcining at 1200℃ for 4 h by analysing X-ray diffraction(XRD). YSCM anode had similar coefficient of thermal expansion (CTE) value with yttria-stabilized zirconia (YSZ) electrolyte by calculating the CTE curve. The fourier transform infrared absorption spectra (FT-IR) demonstrates that the YSCM material shows excellent stability under a 1000 ppm H2S atmosphere. The voltage and maximum power density of YSCM/YSZ/Ag cell were 1.05 V and 145 mW·cm-2 at 800℃ by ananlysis of the curves of voltage-current (V-I) and power-current (P-I).Scanning electron microscope (SEM) was used to observe the YSCM-SDC/YSZ/Ag cell structure. The result showed that the Y0.9Sr0.1Cr0.5Mn0.5O3-δ-Sm0.2Ce0.8O1.9 (YSCM-SDC) anode was well adhered to the YSZ electrolyte. The electrochemical performance of YSCM-SDC anode was superior to that of the La0.75Sr0.25Cr0.5Mn0.5O3-δ (LSCM) anode under equal conditions by the analysis of the I-V and I-P curves. Sr depletion in the YSCM structure and the formation of SrSO4 were found in a 3000 ppm H2S atmosphere by energy dispersive x-ray (EDX) and XRD. The cell experienced a reversible and irreversible performance degradation process during the constant current test. Especially, the voltage decreased at a rate of 31 mV/h and stabilized at 0.49 V under a 3000 ppm H2S atmosphere.To evaluate the effect of hydrogen sulfide on the performance of Ni-Ce0.8Sm0.2O1.9 (Ni-SDC), LSCM and Sr2CoMoO6-δ (SCMO) anodes, a pulse injecting and online gas chromatography technology were utilized. Through comparison of the potential fluctuation under constant current condition for the three anodes, the less potential changes were observed for the LSCM and SCMO anodes. Mass balance of sulfur revealed that a majority of sulfur deposited on the Ni-SDC anode layer after pulse of H2S. Moreover, the generated sulfur-containing compound was extremely stable. The test of electrochemical performance shows that the sulfur poisoning is irreversible after long time pulse of H2S.