Stable solid oxide electrolysis cells with SSF-based symmetrical electrode for direct high-temperature steam electrolysis

Abstract

In order to solve the oxidation problem of the Ni-based solid oxide electrolysis cells (SOECs), SOECs with symmetrical electrode Sm0.5Sr0.5FeO3-δ- Gd0.1Ce0.9O2-δ (SSF-GDC) were systematically investigated, including the steam partial pressure, the working temperature, the electrolysis voltage. The reversible symmetrical cells with SSF-GDC electrode under humidified hydrogen presented good reversibility, and the maximum electrolysis current density was 1025 mA cm−2 at 800 °C with the applied voltage of 2V. In the case of direct N2 with 20% steam partial pressure as fuel, the symmetrical cells generated the maximum electrolysis current density increased from 267 to 1560 mA cm−2 at 650–800 °C. The influence of the steam partial pressure on the steam electrolysis showed that the maximum electrolysis current densities increased with the increase of the steam partial pressure from 3% to 20%, and the steam electrolysis with 3% steam partial pressure showed obvious concentration polarization due to insufficient steam partial pressure at high electrolysis current density. Finally, the short-term stability at different electrolysis voltages and long-term stability at the electrolysis voltage of 1.5V showed that there was no attenuation after 25 h operation, indicating that SSF-based symmetrical electrodes cab be an alternative to Ni-based fuel electrode materials for high-temperature steam electrolysis.