Mechanistic insights into the selective mass-transport and fabrication of holey graphene-based membranes for water purification applications

Abstract

• Critical review on holey graphene (HG)-based membrane for water purification. • HG membranes have high efficiency, selectivity, and superior water permeability. • Mechanistic insights into the mass-transport of HG-based membranes are discussed. • An overview on the fabrication methodologies of HG-based membranes is highlighted. • The performance development of HG-based membranes and challenges are detailed. Graphene (Gr) and its derivative nanomaterials enable a novel approach to manipulate selective mass transport mechanisms at the sub-nanoscale level. These nanomaterials can maintain d-spacing at the sub-nanoscale level amidst their rigid nanosheet frame structure. Unlike other nanomaterials, they have outstanding features such as atomic thickness, extraordinary mechanical strength, and superior chemical stability. Although they could be utilized to overcome crucial challenges in various water purification applications, they usually suffer from swelling and limited penetration. Holey graphene (HG; also known as nanoporous graphene or graphene nano-mesh) is an exceptional derivative of Gr created by eliminating some atoms from the graphite structure to create distributed pores in the atomic structure of Gr nanosheets. These pores, occasionally with ample reactive functional groups near their boundaries, resulted in favorable defects features, which influence the intact Gr nanosheets structure, however they are beneficial in different water purification and desalination applications. In this review, the different approaches for fabricating HG-based membranes along with mass-transport mechanisms including experimental and simulation outcomes are presented and discussed. Related applications that exploit the extraordinary structure of the HG nanomaterial are also reviewed.