Electrical, thermal, and H2O and CO2 poisoning behaviors of PrNi0.5Co0.5O3-δ electrode for intermediate temperature protonic ceramic electrochemical cells

Abstract

PrNi0.5Co0.5O3-δ (PNC) exhibits adequate total electrical conductivity (∼300 S/cm at 400–600 °C) and moisture has no significant effect on it. The thermal expansion coefficient of PNC is 17.6 × 10−6/K by dilatometry and 18.43 × 10−6/K by in situ XRD. PNC also demonstrates chemical stability against H2O and CO2. However, PNC symmetrical cell over proton-conducting BaZr0.4Ce0.4Y0.1Yb0.1O3-δ (BZCYYb4411) electrolyte shows significant H2O and CO2 poisoning when those are introduced into O2–N2 mixture. In comparison, symmetrical cells with PNC electrode over the oxygen ion conducting Ce0.9Gd0.1O2-δ (GDC) electrolyte show no H2O and CO2 poisoning under similar conditions. It is hypothesized that poisoning from H2O and CO2 of the PNC proton conducting symmetrical cell is caused by their adsorption on the BZCYYb4411 electrolyte instead of PNC electrode. Such a hypothesis is supported by the H2O and CO2 adsorption behaviors on PNC and BZCYYb4411 powder surfaces, as measured by temperature programmed desorption (TPD).