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Solid oxide electrolysis cells (SOECs) are highlighted as promising power-to-gas (P2G) devices that can provide a reliable supply of hydrogen gas to store renewable energy. Despite the potential of SOECs, there are many challenges facing their commercialization. In this work, the influence of process parameters and fuel electrode optimization on initial SOEC performance (500 hours) is investigated. Electrolysis experiments were performed with both GDC (gadolinia doped ceria)-infiltrated and uninfiltrated Ni-YSZ (yttria stabilized zirconia) fuel electrodes under various hydrogen flow rates with different ratios of H2-H2O and current densities. All cells marginally improve in performance initially, then undergo a brief period of rapid performance degradation followed by stabilization. The observed three stages of cell performance, in terms of length of time and rate of change, are found to be dependent on the type of fuel electrode and experimental process parameters used.

The performance of composite rare-earth nickelate-rare-earth doped ceria composite oxygen electrodes, with a high concentration of rare-earth doping in ceria to stabilize the nickelate phases are reported. Additionally, the stability of these compositions is reported at both the sintering (1240°C) and operating temperatures (800°C). Specifically, a lanthanum nickelate La2NiO4+δ (LNO) -45 mol% lanthanum doped ceria (LDC45) oxygen electrode has been tested in both solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC) modes. The performance of this cell has been compared with a composite oxygen electrode comprising 20 mol% strontium doped lanthanum manganite (LSM)-10 mol% scandia 1 mol% ceria stabilized zirconia (SSZ) electrode. The LNO–LDC45 composite oxygen electrode shows a 65% increase in current density at 0.8 V, and a 260% increase in current density at 1.2 V compared to LSM-SSZ oxygen electrodes in SOFC and SOEC mode respectively. Additionally, long term performance data shows that this superior performance can be maintained for long operating times at 1.2 V in SOEC mode at 800°C. Supplemental cell tests also show comparable performance for a composite neodymium nickelate Nd2NiO4+δ (NNO)- 50 mol% neodymium doped ceria (NDC50) and a composite LNO- 50 mol% lanthanum doped ceria (LDC50) electrode.