Effective Atomic Layer Deposition of palladium coatings for hydrogen separation membranes

• An original strategy for the synthesis of Pd-based composite membranes was applied using Atomic Layer Deposition (ALD). • The membrane supports were pre-coated with amorphous alumina by ALD before the deposition of Pd. • The highest selectivity to H 2 was obtained at temperatures around 286°C. • The membranes exhibit high stability during temperature cycling and good regenerability after CO exposure. As global energy demand continues to rise, hydrogen purification plays a pivotal role in advancing the “hydrogen economy”, ensuring the required purity levels for its direct use or storage. This work presents the synthesis and functional characterization of palladium-based hydrogen-selective composite membranes applicable for gas separation below 300°C. These membranes were prepared via Atomic Layer Deposition (ALD) of palladium (Pd) onto asymmetric ceramic tubular supports, using palladium hexafluoroacetylacetonate Pd(hfac) 2 and formalin at 220°C. Prior to Pd deposition, the γ-Al₂O₃ top-layer of the support was modified with an ultra-thin (∼1 nm) amorphous alumina layer also deposited by ALD. This strategy enhances the number of nucleation sites for Pd, resulting in the formation of thin, uniform and compact membranes. It also substantially reduces Pd precursor consumption compared to conventional methods. The gas separation factors at 286°C were 86 for H 2 /N 2 , 79 for H 2 /CH 4 and 67 for H 2 /CO 2 . Additionally, the composite membranes demonstrated resilience to repeated temperature cycling and were able to restore their performance after exposure to trace amounts of CO.