PNNL

Abstract

The best solution to address the critical durability issue of solid oxide electrolytic cells (SOECs) for high-efficiency and high-rate H2 production is to lower the operating temperature without sacrificing the performance. Developing high performance oxygen electrodes (OEs) is a key to capitalizing this solution. Here we report on a highly active OE for intermediate temperature ZrO2-based SOECs without a CeO2 barrier layer. The new barrier-layer-free (BLF) OE is a composite of two materials, (Bi0.75Y0.25)0.93Ce0.07O1.5±d (BYC) that exhibits high oxide-ion conductivity and La0.8Sr0.2MnO3 (LSM) that possesses a high electronic conductivity to enable fast oxygen reduction/evolution reactions (ORR/OER). Featuring a microscale porous BYC scaffold decorated with high surface area LSM nanoparticles (NPs), the new BLF-OE exhibited a low area specific resistance (ASR) of 0.10 O cm2 at 650 °C in air. With 50%H2-50%H2O as a feed to hydrogen electrode (HE) and air to OE, the single cell performance achieved 588 mA cm-2 at 0.80 V in the fuel cell mode and 688 mA cm-2 at 1.30 V in the electrolytic mode at 650 °C. Our in-house testing showed that this level of performance was ~3.5? higher than the cell with the benchmark La0.6Sr0.4Co0.2Fe0.8O3-d-Ce0.9Gd0.1O2-d OE. The long-term durability testing under alternating fuel cell and electrolytic modes showed a low degradation rate of 0.10 mA cm-2 h-1 over 550 hours. These encouraging results showed the great promise of the newly developed BYC-LSM to be an excellent OE candidate for intermediate temperature SOECs.