High-purity hydrogen for decarbonization via dopamine-engineered α-Al2O3/graphene oxide membranes: the impact of gas mixture feed composition on H2/CO2 separation

Abstract Ceramic-supported graphene oxide (GO) membranes have been widely employed in gas separation due to their suitable mechanical strength and thermal and chemical stability. However, their large-scale application depends on the proper adjustment of fabrication parameters and permeation conditions. In this study, asymmetric α-alumina (α-Al 2 O 3 ) hollow fiber substrates were fabricated by the phase-inversion method followed by a single sintering step. A polydopamine (PDA) interlayer was deposited on the fiber outer surface to enhance GO adhesion to the substrate. Membrane performance was evaluated over a broad range of feed gas molar compositions, varying the H 2 content from 25 to 75 mol%. The PDA interlayer, containing catechol hydroxyl and amine functional groups and exhibiting a thickness of (154 ± 27) nm, effectively reduced substrate surface roughness from (120.1 ± 5.2) nm to (101.6 ± 6.9) nm, while simultaneously providing functional groups that promoted GO adhesion, thereby enabling the deposition of a more uniform GO coating. The resulting composite membrane, containing a GO selective layer with a thickness of (245 ± 35) nm, exhibited a high H 2 permeance of (2810.8 ± 3.6) GPU and an H 2 /CO 2 separation factor of 27.44 ± 2.92. The best separation performance was obtained for a feed mixture of 75 mol% H 2 and 25 mol% CO 2 , producing a permeate stream with 99 mol% H 2 purity. These results highlight the importance of assessing membrane performance over a wide range of operating compositions to better represent real-world process conditions.