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 H 2 /CO 2 that far exceeded the corresponding 2008 Robeson upper bound. Remarkable separation efficiency of GO membranes for H 2 and bulky C 3 or C 4 hydrocarbons was achieved with high flux and good selectivity at the same time. On the contrary, N 2 and CH 4 molecules, with larger kinetic diameter and simultaneously lower molecular weight, relative to that of CO 2 , remained far from the corresponding H 2 /N 2 or H 2 /CH 4 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 CO 2 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 H 2 /CO 2 or H 2 /alkanes.