Hydrogen flux in La0.87Sr0.13CrO3–δ

Acceptor doped LaCrO3 is a promising material for dense, ceramic hydrogen permeable membranes, displaying hydrogen flux in the order of 10−4 ml min−1 cm−1 in a 10% H2+2.5% H2O/dry Ar gradient at 1000 °C. In this work we have characterized the ambipolar proton electron hole conductivity in La0.87Sr0.13CrO3–δ by means of hydrogen flux measurements. Proton transport parameters were extracted, yielding a pre-exponential factor of 3 cm2 K V−1 s−1 and an enthalpy of mobility of 65 kJ mol−1. Hydrogen flux measurements showed that applying a layer of Pt on both feed and sweep side surfaces significantly altered the temperature dependency and increased the hydrogen flux in a 550 μm thick membrane. This indicates that surface kinetics will limit the hydrogen flux in uncoated membranes. From hydrogen surface exchange measurements, a surface exchange coefficient ranging from 10−10 to 10−8 mol cm−2 s−1 at 325–600 °C was obtained.