Plasma-enhanced atomic layer deposition of titania on alumina for its potential use as a hydrogen-selective membrane

As a clean energy carrier, hydrogen has attracted global attention in recent years, because it could address issues that are related to reducing global climate change. It has to be stipulated that to date's processes for hydrogen production using fossil fuels need to be coupled with CO2 separation and storage. Thermally and hydrothermally stable microporous membranes with intrinsic high H-2/CO2 selectivity are highly demanded in steam-reforming and water gas-shift processes for H-2 gas separation. In this study a composite alumina-titania membrane was synthesized by the combination of atomic layer deposition (ALD) and sol-gel processes. By adjusting the number of ALD cycles (280 cycles), a thin TiO2 layer corresponding to a thickness of similar to 10 nm was deposited on the surface of gamma-Al2O3 membranes. The gas permeation was tested to assess the membranes' gas separation performance. The membranes exhibited a good balance between H-2 permeance and separation properties. At 450 K, the H-2 permeance is approximately 12.5 x 10(-8) mol m(-2) s(-1) Pa-1 and the separation factor is 5.8 for a H-2/CO2 mixture. The results clearly demonstrate that the studied deposition method ALD is a promising route to prepare ceramic microporous membranes for hydrogen separation. (C) 2011 Elsevier B.V. All rights reserved.