The direct use of methane eliminates the need for pre-reformers, thus reducing the complexity, size, and cost of the overall SOFC system. In addition to pure hydrogen, SOFCs can theoretically be operated with hydrocarbon fuels such as methane (the main component of natural gas). Solid oxide fuel cells (SOFCs) are highly efficient energy conversion devices with the characteristics of fuel flexibility and low pollutant emissions. Therefore, the incorporation of cerium in the anode structure could improve the cell lifetime by reducing carbon formation. Carbon deposits were detected mostly on the surface of Ni particles but not near the anode/electrolyte interface or the cerium surface. The low degradation in performance was mainly caused by the increase in charge transfer resistance, which can be attributed to carbon deposition on the anode causing a reduction in the number of active centers. The cell was operated for more than 900 h in CH 4 and 806 h under load demand, with a low degradation rate of ~0.2 mV Impedance spectra of the cell showed that at least three processes govern the direct electrochemical oxidation of methane on the Ni-CYSZ anode and these are related to charge transfer at high frequency, the adsorption/desorption of charged species at medium frequency and the non-charge transfer processes at low frequency. Similar cell performance was observed with wet (3% H 2O) and dry CH 4, and this indicates that the presence of water is not relevant under the applied load demand. Material analysis was carried out by SEM-EDS after operation was complete. cm –2 in wet CH 4 for 236 h and dry CH 4 for 526 h at 850 ☌ in order to assess the cell stability. Long-term tests were subsequently conducted under 180 mA Initially, the electrochemical behavior was investigated under several load demands in wet (3% H 2O) CH 4 at 850 ☌ during 144 h using I-V curves, impedance spectra, and potentiostatic measurements.
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