Development of hydrogen-selective TiO_xN_y-Pd composite membrane materials by atomic layer deposition

This work reports on novel hydrogen (H₂) selective membrane composed of TiO_xN_y-Pd nanocomposite thin films prepared by Atomic Layer Deposition (ALD) on asymmetric porous alumina supports. The nanocomposite combines the robustness of a ceramic matrix, selective gas barrier properties of TiO_xN_y thin layer and specific H₂ sorption/affinity of palladium nanoparticles (Pd NPs). Precise control of the thickness and chemical composition of TiO_xN_y-Pd layer enables to achieve promising H₂ selectivities (α_H2/N2≈35 and α_H2/He≈7) with permeances π_H2≈228GPU at 390 °C. At this temperature, TiO_xN_y crystallites start to form in the initially near-amorphous layer and allow selective transport of H atoms generated during the adsorption-dissociation of H₂ on the Pd NPs. This study clearly stresses the effectiveness of ALD in the formation of dense H₂-permselective membranes while significantly limiting the production costs by reducing the content of expensive elements, such as Pd. Finally, thanks to the versatility of the ALD technique, the present strategy could be extended to other rational design for applications requiring gas separation or detection.