Thin, High-Flux, Self-Standing, Graphene Oxide Membranes for Efficient Hydrogen Separation from Gas Mixtures

The preparation and gas-separation performance of self-standing, high-flux, graphene oxide (GO) membranes is reported. Defect-free, 15–20 μm thick, mechanically stable, unsupported GO membranes exhibited outstanding gas-separation performance towards H₂/CO₂ that far exceeded the corresponding 2008 Robeson upper bound. Remarkable separation efficiency of GO membranes for H₂ and bulky C₃ or C₄ hydrocarbons was achieved with high flux and good selectivity at the same time. On the contrary, N₂ and CH₄ molecules, with larger kinetic diameter and simultaneously lower molecular weight, relative to that of CO₂, remained far from the corresponding H₂/N₂ or H₂/CH₄ upper bounds. Pore size distribution analysis revealed that the most abundant pores in GO material were those with an effective pore diameter of 4 nm; therefore, gas transport is not exclusively governed by size sieving and/or Knudsen diffusion, but in the case of CO₂ was supplemented by specific interactions through 1) hydrogen bonding with carboxyl or hydroxyl functional groups and 2) the quadrupole moment. The self-standing GO membranes presented herein demonstrate a promising route towards the large-scale fabrication of high-flux, hydrogen-selective gas membranes intended for the separation of H₂/CO₂ or H₂/alkanes.