Selective gas permeation through polymer-hybridized graphene oxide nanoribbon nanochannels: Towards enhanced H2/CO2 selectivity

Abstract

Two-dimensional materials have garnered significant attention as membrane building blocks for their tunability, which enables simultaneous enhancement of permeance and selectivity. This study investigates the impact of reduced nanosheet width on H2/CO2 separation by examining the gas permeation behavior of graphene oxide nanoribbon (GONR)/polymer hybrid membranes. Polymers are incorporated into the macroporous GONR scaffold to accelerate H2 transport due to the expansion of GONR nanochannels. The GONR/polymer scaffolds can be coated on porous support by using the scalable shear coating method, resulting in micrometer-scale selective layers. The carbon layers remain intact after polymer hybridization and inhibit polymer crystallization, allowing strong polymer-CO2 interactions to hinder CO2 permeation. However, the excessive polymer composition can compromise GONR-polymer hybridization and crystallization suppression. We also explore the effect of polymer charge on gas separation performance. A relatively small amount of cationic polymer enhances H2/CO2 selectivity, but the enhancement is limited due to strong electrostatic interactions. Anionic polymer-GONR hybridization also improves gas separation performance, but is less effective compared to neutral polymer, as repulsive interactions result in a looser structure. The gas separation performance of the optimized membrane (GONR/PEO 25 wt%) shows H2 permeability of 7,108 Barrer and H2/CO2 selectivity of 10.8, surpassing the Robeson upper bound for polymeric membranes and comparable to that of previous 2D-materials-based membranes. Our finding demonstrates that GONR nanochannels and their gas transport properties can be tuned by simply adding polymers depending on the quantity, molecular weight, and charge of the polymers.