Atom‐Thick Membranes for Water Purification and Blue Energy Harvesting

Abstract

Membrane-based processes such as water purification and harvesting of osmotic power deriving from the difference in salinity between seawater and freshwater, are two strategic research fields holding great promises for overcoming critical global issues like the world growing energy demand, the climate change and the access to clean water. Ultrathin membranes based on two-dimensional materials (2DMs) are particularly suitable for highly selective separation of ions and effective generation of blue energy, because of their unique physicochemical properties and novel transport mechanisms occurring at the nano-and sub-nanometer length scale. However, due to the relatively high costs of fabrication compared to traditional porous membrane materials, their technological transfer towards large-scale applications still remains a great challenge. Herein, we present an overview of the current state-of-the-art in the development of ultrathin membranes based on 2DMs for osmotic power generation and water purification. We discuss several synthetic routes to produce atomically-thin membranes with controlled porosity and we describe in detail their performances, with a particular emphasis on pressure retarded osmosis and reversed electrodialysis methods. In the last section, outlooks and current limitations as well as viable future developments in the field of 2DMs membranes are provided.3

Ultrafast water‐selective permeation through graphene oxide membrane with water transport promoters

“…Two‐dimensional (2D) materials with atomic thickness, exemplified by graphene oxide (GO), have emerged as promising nano‐building blocks for next‐generation high‐performance separation membranes due to their capability to construct ultrathin selective layer with controllably ordered interlayer nanochannels, featuring extraordinary permeation properties . Laminar GO membranes have demonstrated attractive gas separation efficiency owing to the sharp size‐exclusion effect from the well‐defined interlayer spacing . However, during the operation in aqueous environment, the hydrophilic GO interlayer channels can adsorb a large amount of water molecules, which subsequently lead to an enlarged interlayer spacing (swelling) or even membrane delamination .…”

Up-scalable emerging energy conversion technologies enabled by 2D materials: from miniature power harvesters towards grid-connected energy systems

“…15 for real demonstrations) [38][39][40][41][42][43][44][45] and fuel cells [51][52][53][54] for the hydrogen (H 2 ) or methanol economy and their associated mobility to stationary power stations, can cover the main energy needs of the city and transportation, respectively. Furthermore, demonstrated salinity gradient plants and streaming potential harvesters installed at rivers/sea boundaries, 49 as well as various smart ways of harvesting water energy such as evaporation-or moisture-based, 11,50 all enabled by GRM, can revolutionize the way grid-electricity is provided in the near future. few atomic layers (Fig.…”

“…Although the aforementioned approaches are very appealing, they require external stimulus of pressure, salinity-gradient, or the development of sophisticated membranes, thereby restricting their current wide usage. 11,50,298 Other approaches exist with less demanding infrastructure requirements based on triboelectric, electrokinetic, or piezoelectric effects towards transforming the motion of water into electrical energy. 15,299 Specifically, an electronic double layer is formed at the interface between a charged solid surface and a fluid.…”

Generation of Osmotic Power from Membrane Technology

“…Osmotic power generation using 2D materials are also once of the good choice, to make thin layer by incorporating 2D materials, while interfacial polymerization, the membranes produce clean blue energy. In it possible due to materials' unique properties and novel transport mechanisms occurring at the nano and sub-nanometer length scale [55]. Two different polyethylene glycol (PET) of molecular weight 4,000 and 6,000 g/mol were used for the development of CA membranes by Sharma et al [56].…”