Controllable ion transport by surface-charged graphene oxide membrane

Mengchen Zhang,Gongping Liu,Nanping Xu,Yufan Ji,Kecheng Guan,Wanqin Jin

doi:10.1038/s41467-019-09286-8

Mengchen Zhang, Gongping Liu + Show 4 more

Open Access

https://doi.org/10.1038/s41467-019-09286-8

Copy DOI

Abstract

Ion transport is crucial for biological systems and membrane-based technology. Atomic-thick two-dimensional materials, especially graphene oxide (GO), have emerged as ideal building blocks for developing synthetic membranes for ion transport. However, the exclusion of small ions in a pressured filtration process remains a challenge for GO membranes. Here we report manipulation of membrane surface charge to control ion transport through GO membranes. The highly charged GO membrane surface repels high-valent co-ions owing to its high interaction energy barrier while concomitantly restraining permeation of electrostatically attracted low-valent counter-ions based on balancing overall solution charge. The deliberately regulated surface-charged GO membranes demonstrate remarkable enhancement of ion rejection with intrinsically high water permeance that exceeds the performance limits of state-of-the-art nanofiltration membranes. This facile and scalable surface charge control approach opens opportunities in selective ion transport for the fields of water transport, biomimetic ion channels and biosensors, ion batteries and energy conversions.

Highlights

Ion transport is crucial for biological systems and membrane-based technology
X-ray photoelectron spectroscopy (XPS; Supplementary Fig. 8) and infrared (IR; Supplementary Fig. 9) spectra of surface-charged graphene oxide (GO) membranes showed newly introduced functional groups on the GO membrane surface derived from the top polyelectrolytes
Protonation of amine groups or deprotonation of sulfonic/carboxyl/hydroxyl groups in water accounted for the charge properties of the membrane surface, which could be finely tuned by the intensity and amount of these ionizable functional groups

Summary

GO-PSS

Inspired by the charge interaction principle and the function of biological ion channels, we demonstrate a strategy of creating surface charges on GO membrane to realize controllable ion transport without impeding water filtration though the GO membrane. Tunable charges attached on the surface of pre-stacked GO laminates exhibited dominant electrostatic repulsion against doubly charged co-ions (with charge like the membrane surface charge) while suppressing weak electrostatic attraction toward singly charged counter-ions (with charge unlike the membrane surface charge). By manipulating the charge interactions between the membrane surface and the ions in water, transport of ions from typical AB2- or A2B-type salts can be prevented while the water remains free to permeate through the membrane (Fig. 1a)

Results

60 Commercial membranes

Methods

RT ðΔP