Atomic layer deposited aluminium oxide membranes for selective hydrogen separation through molecular sieving

Abstract

Ultra-thin membranes have significant potential for the gas separation. However, the fabrication of ultra-thin membrane with high selectivity and permeance remains a challenge. Herein, we develop a high-performance hydrogen separation membrane using atomic layer deposition (ALD) method to deposit ultra-thin Al2O3 layer (ALD-Al2O3) on a porous anodic aluminum oxide (AAO) support. The pore openings of the AAO substrate were fully covered, but not sealed, by the Al2O3 overlayer after 260 ALD cycles. Due to the low deposition temperature (50 °C), angstrom-scale pores were formed within the Al2O3 overlayer. Single gas permeance results revealed that the size of the pores to be smaller than 0.364 nm, but larger than the kinetic diameter of molecular H2 (0.289 nm). This membrane at room temperature, exhibits high H2 permeance of ∼3.03 × 10−7 mol m−2 s−1 Pa−1 and high H2 selectivity for H2/CO2 (5148.2), H2/O2 (120.7), H2/N2 (161.5) and H2/CH4 (219.5), showing great potential for industrial H2 purification and recovery.