Hydrogen isotope separation using graphene-based membranes in liquid water

TL;DR

This study demonstrates a novel graphene-based membrane system for effective hydrogen isotope separation from water, highlighting improved membrane stability, defect repair, and a new proton transport model based on kinetic isotope effects.

Contribution

It introduces a new membrane architecture using graphene on PITEM substrate with defect repair, and proposes a model explaining proton transport via graphene for isotope separation.

Findings

High separation factor achieved for H/D in water.

Graphene membrane maintains integrity and avoids swelling issues.

Proposed model explains proton transport mechanism based on KIE.

Abstract

Hydrogen isotope separation has been effectively achieved using gaseous H2/D2 filtered through graphene/Nafion composite membranes. Nevertheless, deuteron nearly does not exist in the form of gaseous D2 in nature but in liquid water. Thus, it is a more feasible way to separate and enrich deuterium from water. Herein we have successfully transferred monolayer graphene to a rigid and porous polymer substrate PITEM (polyimide tracked film), which could avoid the swelling problem of the Nafion substrate, as well as keep the integrity of graphene. Meanwhile, defects in large area of CVD graphene could be successfully repaired by interfacial polymerization resulting in high separation factor. Moreover, a new model was proposed for the proton transport mechanism through monolayer graphene based on the kinetic isotope effect (KIE). In this model, graphene plays the significant role in the H/D separation process by completely breaking the O-H/O-D bond, which can maximize the KIE leading to prompted H/D separation performance. This work suggests a promising application of using monolayer graphene in industry and proposes a pronounced understanding of proton transport in graphene