Tuneable Permeability to H₂, CO₂, He, and Ar in Graphene Oxide-PDDA Self-Assembled Multilayers, Yielding Good Selectivity at High Flux

Today, the most effective and suitable method to obtain molecular H-2 is the extraction from mixtures where it is present, using gas-sieving membranes. To this aim, the preparation and characterization of layered nano-composites are described, made of alternated layers of positively charged Poly(Diallyl Dimethyl Ammonium chloride) (PDDA) and negatively charged graphene oxide (GO) nanosheets with high and tunable selectivity for H-2 purification. The composites are assembled exploiting electrostatic interactions and the layer-by-layer technique; this study correlates permeance tests with changes in chemical composition and structure of the material using X-rays Photoelectron Spectroscopy, X-rays diffraction water contact angle, and surface zeta-potential measurements. Thanks to its layered nature, the GO-PDDA composite shows an excellent selectivity, allowing faster permeation of H-2 as compared to CO2 and Argon. By transforming the GO to reduced GO, the porosity of the nanosheets can be further increased, in this way increasing the permeance of the material and its selectivity at the same time, thus allowing to overcome the Robeson limit, the technological upper boundary to the performance of actual membranes.