High performance solid oxide electrolysis cells using Pr0.8Sr1.2(Co,Fe)0.8Nb0.2O4+δ-Co-Fe alloy hydrogen electrodes

A novel ceramic hydrogen electrode material consisting of K2NiF4-type structured Pr0.8Sr1.2(Co,Fe)0.8Nb0.2O4+δ (K-PSCFN) matrix with homogenously dispersed nano-sized Co-Fe alloy (CFA) has been demonstrated by annealing perovskite Pr0.4Sr0.6Co0.2Fe0.7Nb0.1O3−δ (P-PSCFN) in H2 at 900 °C. Impedance spectra and voltage-current density curves of the La0.8Sr0.2Ga0.83Mg0.17O3−δ (LSGM) electrolyte supported solid oxide electrolysis cell (SOEC) with a configuration of K-PSCFN-CFA/LSGM/Ba0.9Co0.7Fe0.2Nb0.1O3−δ (BCFN) have been evaluated as a function of the operating temperature and feeding gas absolute humidity (AH) to characterize the cell performance. Cell polarization resistances (Rp) were as low as 0.77 and 0.31 Ω cm2 under open circuit voltage (OCV) and 60% absolute humidity (AH) at 800 and 900 °C, respectively. The cell has demonstrated good stability for high temperature stream electrolysis, and a hydrogen production rate of 707 ml/cm2 h calculated from the Faraday's law has been achieved under an electrolysis voltage of 1.3 V and 60 vol.% AH at 900 °C. The cell performance results indicate that K-PSCFN-CFA is a promising hydrogen electrode for high temperature solid oxide electrolysis cells.