Development of Mixed-Conducting Membranes for Hydrogen Separation
The membrane consists of a Ni-BZCYYb dense layer supported by a porous Ni-BZCYYb. The first part of the work identifies the optimal hydrogen flux through variation of the nickel content in an asymmetric dense Ni-BZCYYb pellet. The determination of the transference number for the ceramic phase allows us to optimize the electrical conductivity brought on by the nickel. The hydrogen flux through the Ni-BZCYYb was determined as a function of membrane thickness and hydrogen partial pressure. The hydrogen flux was determined by using a mass spectrometer, which correlates the measured hydrogen partial pressure to amount of hydrogen present in a known sweeping gas atmosphere. Results have shown a hydrogen flux of 0.714 ml/cm2min under 100% hydrogen at 750˚C.
The microstructure also plays an important role in the performance of an asymmetric permeation membrane. For dense ceramic membranes, the ohmic permeation resistance from the proton conduction is inversely proportional to the thickness of the membrane. By using a tape-cast method, the thickness of the dense layer can be tailored down to about 10 microns. The results demonstrate an optimized membrane in terms of nickel content and thickness of asymmetric dense/porous layers. This demonstrates the ability to fabricate a cermet hydrogen permeation membrane using a large-scale, industry method.
Further, various catalysts that may enhance hydrogen adsorption, dissociation, and oxidation on the surface of the hydrogen separation membranes are also explored and will discussed in the presentation.