Investigating viability of low temperature co-sintering to produce Ni-YSZ supported solid oxide electrolysis cells with a Ni-GDC active layer

Solid oxide cells (SOC) are attractive for large scale electrolysis because of their unmatched efficiency. The current performance limitation for fuel electrode supported cells, is the Ni-YSZ fuel electrode, which suffers critical degradation at high current density. This limits their hydrogen production capacity. Aiming to overcome said limitation, this work demonstrates the integration of Ni-GDC (Ce0.9Gd0.1O1.95) fuel electrodes into co-sintered thin electrolyte cells. Ni-GDC is widely used in electrolyte supported cells without signs of similar degradation. The novelty of the manufacturing approach adopted was to reduce the co-sintering temperature to 1250 ∘C to limit detrimental interdiffusion between GDC and the zirconia-based electrolyte. It was possible to make testable and gas-tight cells at 1250 ∘C, and the temperature reduction was effective at reducing interdiffusion. However, microstructural characterization of the realized cells documented poor contact between GDC in the fuel electrode and the ScYSZ electrolyte (Sc2O3-Y2O3 stabilized ZrO2). This was the main cause for an approximate 50 pct drop in electrochemical performance compared to cells with Ni-YSZ electrodes. Despite the poor performance, the long-term stability was found to be improved relative to Ni-YSZ fuel electrode cells. One test operating between −1 and −1.75 A/cm2 for more than 500 h showed no Ni migration. Moreover, it was found that this cell layout did not suffer mechanical failure despite large chemical expansions of GDC. If future work can solve the electrode-electrolyte contact issue, the reported cell concept has the potential to enable a significant increase in the area specific hydrogen production capacity of SOCs.