A novel concept for H permeable membrane proposed here was the use of oxide composites consisting of proton and electron conducting oxides. Composites with the overall composition of (1−y)(SrZrO3)−y(SrFeO3) were chosen as a model membrane to investigate the electrical and the H permeation properties. In this system, it was expected that Fe-doped SrZrO3 phase and SrFeO3-based phase individually form the pathways of protons and electrons, respectively. As expected, considerable H permeation was observed across the oxide composites for y = 0.05, 0.1 and 0.2 using Pt as a surface catalyst. The H permeation fluxes were well described by assuming the ambipolar-diffusion-like kinetics for y = 0.1 and 0.2 at 1173K. However, the observed H fluxes became smaller than the estimated ones as temperature and/or the content of SrFeO3-based phase decreased, suggesting the remarkable contribution of surface reaction to the kinetics of H permeation.

Hydrogen Permeability and Electrical Properties in Oxide Composites. A.Unemoto, A.Kaimai, K.Sato, K.Yashiro, H.Matsumoto, J.Mizusaki, K.Amezawa, T.Kawada: Solid State Ionics, 2008, 178[31-32], 1663-7