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Reliability and durability are two major problems restricting for Solid oxide fuel cells (SOFCs) industrial applications. To ensure the long-term stability, understood the internal operation mechanism of SOFC was necessary. The polarization curve combined with the distribution of relaxation times (DRT) method to analyze the electrochemical impedance spectroscopy (EIS) was used to identify the SOFCs modulation and degradation effect through the excitation frequency. Dynamic evolution of carbon deposition process and specific time constants were determined employing EIS and DRT. Special attention was paid to the dependency between the complex reaction processes that occur during the different operation of SOFC. The corresponding frequencies of concentration and activation polarization resistances in EIS were investigated under various gas compositions. The high concentration polarization resistance caused by the addition of nitrogen and hydrogen starvation was the key limiting factor for high cell power density. The total polarization resistance increased from 1.50 Ω/cm2 to 5.26 Ω/cm2 when the H 2 :N 2 ratio decreased from 1:0 to 1:5. The anode did not deteriorate due to the poisoning of Ni particles in a short-term tested under 0.5 A/cm2 current density when the fuel was methane. • Modulation and degradation evaluation for SOFCs. • Detailed electrochemical investigation of anode-supported button SOFCs. • The addition of nitrogen significant increase the concentration polarization resistance. • The influence of fuel composition on the electrical performance of SOFCs. • Dynamic evolution of carbon deposition was observed by means of EIS and DRT. [ABSTRACT FROM AUTHOR]

• Tubular PCFC with effective area of 2.3 cm2 is fabricated by dip-coating technique. • It shows high performance at reduced temperature, giving 465 mW cm−2 at 600 °C. • The cell outputs 118 mW cm−2 at 450 °C and reveals detectable power at 200 °C, 3 mW. • Cell stability is tested for 30 h, at a constant voltage of 0.7 V under 600 °C. • Performance declines first and then tend to be stable during stability test. An anode-supported tubular protonic ceramic fuel cell with BaCe 0.7 Zr 0.1 Y 0.2 O 3-δ electrolyte is fabricated using dip-coating technique. Electrochemical performances of the cell are tested at temperatures from 600 to 200 °C, utilizing humidified H 2 (3 vol% H 2 O) as fuel and ambient air as oxidant. With an effective area of 2.3 cm2, the cell yields a peak power density of 465 mW cm−2 at 600 °C and 118 mW cm−2 at 450 °C. Even when the temperature is as low as 200 °C, there is still an output power of 3 mW. Stability of the cell under 600 °C is tested by operating the cell at a constant voltage of 0.7 V. The test lasts for 30 h during which the operating power density decreases rapidly in the first 10 h, then tend to be stable at 300 mW cm−2. [ABSTRACT FROM AUTHOR]