Hydrogen flux in La0.87Sr0.13CrO3–δ

Abstract

Acceptor doped LaCrO3 is a promising material for dense, ceramic hydrogen permeable membranes, displaying hydrogen flux in the order of 10−4mlmin−1cm−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 3cm2KV−1s−1 and an enthalpy of mobility of 65kJmol−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 550μm 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 10−8molcm−2s−1 at 325–600°C was obtained.