Water-Assisted Permeation of Gases in Carbon Nanomembranes.

Planar nanomaterials finished with transverse ducts represent an intriguing avenue for exploring interfacial phenomena. Due to their small thickness, the kinetics of molecular diffusion across the channels is likely to be dominated by entrance events. Therefore, measuring transport rates in freestanding films can yield valuable information on surface processes. In this work, we study permeation of gases in carbon nanomembranes (CNMs) when accompanied by saturated water vapor. The experimental data reveal a manifold increase in transmembrane fluxes compared to dry conditions. Gas molecules are found to be trapped in adsorbed water, which enhances their translocation likelihood. We demonstrate that the permeance correlates with the vapor relative pressure and discuss the observed crossing mechanism in terms of water condensation and Henry's law. Our findings provide guidance for designing gas separation membranes upon two-dimensional materials.