Gd_(0.2)Ce_(0.8)O_(1.9)(GDC)-Gd_(0.08)Sr_(0.08)Ti_(0.95)Al_(0.05)O_(3±δ)(GSTA) is a mixed oxygen ionic and electronic conducting composite developed for hydrogen separation. By removing oxygen from steam using the membrane at elevated temperature, a H_2-rich steam-hydrogen mixture was obtained. Generally, a permeation process is controlled by surface exchange reactions as well as bulk diffusion process of charged species. However, when the membrane thickness is less than a critical thickness, the permeation flux cannot be increased significantly by further decreasing the thickness of the membrane since the permeation process is surface reaction controlled. In order to improve the surface exchange reaction and thereby increase the permeation flux from the membrane, a NiO/GDC surface catalyst was applied onto the surface of GDC-GSTA bare sample. The effect of surface catalyst on transport properties of the MIEC membrane was investigated using electrical conductivity relaxation (ECR) method and hydrogen generation experiments.
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