Hydrogen selective palladium-alumina composite membranes prepared by Atomic Layer Deposition

We report a novel strategy enabling the fabrication of hydrogen selective palladium-alumina (Pd/Al2O3) composite membranes using Atomic layer Deposition (ALD). The ALD of palladium was based on the reaction of palladium hexafluoroacetylacetonate Pd(hfac)2 and formalin at 220 °C, and allowed for the preparation of embedded Pd nanoclusters confined within the pores of a γ-Al2O3 membrane layer on a tubular ceramic support. Gas permeation and separation measurements of the prepared membranes were carried out and values above 1000 GPU were measured for the hydrogen flux. Promising permselectivities have been obtained at a moderate temperature of 188 °C (α*H2/N2 ~ 23 and α*H2/CO2 ~ 13) together with attractive separation factors of FH2/N2 ~ 16 and FH2/CO2 ~ 9. The presented results demonstrate the proof of concept for the fabrication of hydrogen selective Pd/Al2O3 composite membranes using ALD. Furthermore, this strategy could be extended to the design of other gas selective or catalytic membrane materials, composed of different metals and their alloys conformally deposited on tubular ceramic supports with high surface to volume ratio.