Fabrication of Porous Supported MIEC Dense Thin Coating for Hydrogen Separation

Decomposition of steam under a chemical driving force at moderate temperatures offers a simple and economical way to generate hydrogen. Significant amounts of hydrogen can be separated by splitting steam and removing the oxygen using Gd0.2Ce0.8O1.9-Gd0.08Sr0.88Ti0.95Al0.05O3{plus minus}δ mixed ionic and electronic conductors. Hydrogen generation experiments for the self-standing thick membranes and porous supported thin membranes have been conducted at different oxygen pressure gradients across the membranes and steam contents on the steam side. Experimental results indicate that the hydrogen generation process is controlled by the bulk diffusion for the thick membranes, while the permeation process for the thin membranes is mixed controlled, i.e. the process is controlled by surface exchange reactions and the oxygen bulk diffusion. A mathematical model for the calculation of the area specific hydrogen generation rate is proposed based on the measured oxygen partial pressures, gas compositions of the inlet and outlet gases on the steam side.