Supported Meso-Porous Ceria Membranes

Supported meso-porous ceria membranes are made by dip or film coating of ceria precursor dispersions on porous supports.  The precursor dispersions are prepared by sono-chemical precipitation of aqueous ammonium-cerium nitrate at low p_H, followed by chemical precipitation with TMAOH, further sonification and stabilization with bicene.  Excess salt is removed by dialysis.  Thus-treated dispersions consist of primary particles with a narrow size distribution around 5 nm.  A Gd substitution is introduced by adding gadolinium nitrate to the solution before sonification.  To promote layer formation either PVA or PVP is added to the precursor dispersions.  The final membrane structure can be formed on either polymer or ceramic supports by conventional or rapid thermal processing.  Depending on the deposition and thermal processing conditions, dense or meso-porous layers are formed.  For the latter, pore sizes as small as 3 nm have been found.  The membranes are used as scaffolds for micro-porous and dense membrane modifications, intermediate layers, fuel cell electrolytes, and nano-filtration.  The fuel function has been demonstrated for <100 nm thick dense Ce_0.9Gd_0.1O_1.95 electrolytes.  Dilute aqueous salt rejection of meso-porous ceria membranes was found to be better than that of state of the art titania membranes.