Enhanced Hydrogen Permeation in Nanocrystalline Proton Conducting Ceramics of the Form SrCeO3

Implementing this technology to create dense, nanocrystalline ceramics or thin films on porous supported substrates would result in enhanced hydrogen permeation membranes.

Because electron conductivity has been demonstrated to be the limiting factor for hydrogen permeation, any increase in this value results in enhanced permeation:

• In oxide structures exposed to a reducing hydrogen atmosphere, oxygen is removed from the SrCeO3 lattice due to solid/vapor equilibrium.

• The resulting positively-charged oxygen vacancy is intrinsically compensated by an electron from the lattice (Ce+4 to Ce+3 reductions) to maintain a balance of charge.

• It follows that the concentration of electrons and level of electronic conductivity is proportional to the oxygen non-stoichiometry. Smaller particles of SrCeO3 derived from solution synthesis routes lose more oxygen than larger particles, thus having higher levels of electronic conductivity.

This invention provides a novel way to modify materials’ conductivity without changing the ratio of chemical constituents or adding secondary conductive phases by altering the materials’ microstructure. This concept has been proven on the bench test level by synthesizing SrCeO3 powders of various sizes and examining their physical structure and weight loss characteristics at elevated temperature under hydrogen-containing environments. The principle of electron compensation for oxygen vacancies indicates that nano-crystalline powders have enhanced electronic conductivity as compared to larger bulk counterparts.