Electrochemical performance and stability of PrO1.833 as an oxygen electrode for solid oxide electrolysis cells.

Significant efforts have recently been undertaken to develop highly efficient solid oxide cells for high-temperature steam electrolysis (SOEC). Implementing new materials and microstructures that would improve the performance and durability of this technology remains a major issue. For this purpose, a nano-structured PrO 1.833 material coated by the electrostatic spray deposition (ESD) technique was studied as a promising active oxygen electrode for SOEC application. The study was performed considering the PrO x as the functional layer and strontium-doped lanthanum manganite (LSM) as the current collecting layer on a standard half-cell supported by a typical Ni-YSZ cermet, a YSZ electrolyte, and a gadolinium-doped ceria (GDC) barrier layer. The electrochemical characterizations showed promising initial performance at 700 °C in SOEC mode (− 1 A cm−2 at 1.4 V with H 2 O/H 2 = 90 vol%/10 vol%). In addition, a reasonable degradation rate of ∼5.8% kh−1 was obtained at 700 °C within 1000 h of SOEC operation. The structural and elemental evolutions were analyzed with micrometer size resolution all along the functional layer thickness using synchrotron μ-X-ray diffraction and fluorescence. The electrode degradation was primarily attributed to the phase transitions of PrO 1.833. In particular, the structural analyses of the sample aged under applied current revealed a small quantity of PrO 1.5≤x≤1.7 phase at the GDC/AFL (active functional layer) interface which is expected to be less conductive than PrO 1.833 , along with PrO 1.714 and GDC phases. Finally, additional structural characterizations were performed on samples annealed at different temperatures and dwell times: 700 °C for 1000 h and 800 °C for 700 h, respectively. The results are discussed to provide a better understanding of the stability of the praseodymium oxide. • SOEC long-term test of a nanostructured PrO x electrode. • No significant interdiffusion of the chemical elements detected by SEM-EDX. • Phase decomposition characterized by synchrotron μ-XRD and μ-XRF. • Only ∼5.8% kh−1 degradation rate obtained at 700 °C for 1000 h of SOEC operation. • A better understanding of the aging of nanostructured PrO x for electrolysis. [ABSTRACT FROM AUTHOR]