Graphene oxide (GO) has shown great potential as a membrane material due to its unique properties, including high mechanical strength, excellent thermal stability, versatility, tunability, and outperforming molecular sieving capabilities. GO membranes can be used in a wide range of applications, such as water treatment, gas separation, and biological applications. However, the large-scale production of GO membranes currently relies on energy-intensive chemical methods that use hazardous chemicals, leading to safety and environmental concerns. Therefore, more sustainable and greener approaches to GO membrane production are needed. In this review, several strategies proposed so far are analyzed, including a discussion on the use of eco-friendly solvents, green reducing agents, and alternative fabrication techniques, both for the preparation of the GO powders and their assembly in membrane form. The characteristics of these approaches aiming to reduce the environmental impact of GO membrane production while maintaining the performance, functionality, and scalability of the membrane are evaluated. In this context, the purpose of this work is to shed light on green and sustainable routes for GO membranes’ production. Indeed, the development of green approaches for GO membrane production is crucial to ensure its sustainability and promote its widespread use in various industrial application fields.

Graphene oxide (GO) membranes have been proved to be ion-selective thanks to their oxidized functional groups, which are naturally present on its surface. This ion selectivity, together with good mechanical strength, low cost, and simple synthesis, makes GO a great alternative material to conventional costly polymers for the production of ion-exchange membranes. This work focuses on how to produce GO membranes as ion-exchange membranes with a scalable approach and tunable permselectivity. Their physicochemical properties were subsequently investigated by means of selected characterization techniques. Results showed that GO membranes present good ion selectivity and size exclusion towards monovalent cations, reaching a permselectivity of up to 96%. Interestingly, UV-light irradiation of GO membranes can also be proposed as a green reduction method. GO reduction increases the permselectivity due to both a decrease in the dimension of the nanochannels and a reduction in the swelling degree of the membranes. The addition of binders was also investigated to improve the membranes’ mechanical properties. Finally, the ionic resistance of the membranes was measured by impedance spectroscopy, achieving 4.6 Ω cm², orders of magnitude lower than the state-of-the-art graphene oxide-based membranes.

Graphene oxide (GO) has been extensively studied for fabricating ion exchange membranes. This material is of interest due to its surface‐governed charge which, combined with the interlayer distance between the GO flakes stack, offers ion selectivity. However, obtaining high‐performing membranes with high ion selectivity and low ionic resistance remains challenging. To address this issue, Al(OH)₄⁻ anions are incorporated into graphene oxide membranes to increase their spontaneous negative surface charge. The anions are successfully formed and encapsulated through a reaction with the alumina support under alkaline conditions during the membrane fabrication. A modeling of the system proves the anchoring of the Al(OH)₄⁻ anions within the GO matrix. The incorporation of these anions significantly improves the permselectivity and reduces the ionic resistance, reaching approximately 95% and 2 Ω cm², respectively. The GO‐modified membranes also present mono‐valent selectivity, which can boost reverse electrodialysis power densities.

Energy harvesting from water flow or evaporation is recently reported exploiting carbon‐based materials. The water‐carbon dualism is at the base of this phenomenon thanks to a charge redistribution at the liquid/solid interface. Many kinds of approaches and nanomaterials are proposed for this purpose. The main properties under investigation are the surface functionalization and the porosity of carbon‐based materials. In this context, the exploitation of a stacked graphene oxide (GO) membrane as layered nanochannels for water flow energy harvesting is proposed. At the best of this study's knowledge, GO membranes are never reported for this application. The flow is spontaneously induced by both capillarity and evaporation when part of the membrane is incubated in water. In this study, zero‐energy is externally provided allowing sustainable energy production without sub‐products. Different GO membranes are tested for this purpose reaching a maximum open circuit voltage of ≈450 mV and maximum current of ≈100 nA.

Permselectivity of a membrane is central for the development of electrochemical energy storage devices with two redox couples, such as redox flow batteries (RFBs). In RFBs, Br₃⁻/Br⁻ couple is often used as a catholyte which can cross over to the anolyte, limiting the battery’s lifetime. Naturally, the development of permselective membranes is essential to the success of RFBs since state-of-the-art perfluorosulfonic acid (PFSA) is too costly. This study investigates membranes of graphene oxide (GO), polyvinylpyrrolidone (PVP), and imidazole (Im) as binder and linker, respectively. The GO membranes are compared to a standard PFSA membrane in terms of ionic conductivity (Na⁺) and permselectivity (exclusion of Br⁻). The ionic conduction is evaluated from electrochemical impedance spectroscopy and the permselectivity from two-compartment diffusion cells in a four-electrode system. Our findings suggest that the GO membranes reach conductivity and permselectivity comparable with standard PFSA membranes.

This study explores enhancing salinity gradient power using 2D materials due to their surface-governed charge. However, achieving high-performing membranes with superior ion selectivity and low ionic resistances remains challenging. To address this issue, Al(OH) ₄ ^- anions were incorporated into graphene oxide membranes to increase their spontaneous negative surface charge. The anions were successfully formed and encapsulated through a reaction with the alumina support under alkaline conditions during the membrane formation. The membranes’ physicochemical properties were analyzed by means of selected characterization techniques. The incorporation of Al(OH) ₄ ^- anions significantly improved permselectivity and ionic resistance, reaching approximately 95% and 2 Ω cm ² , respectively. A modeling of the system was carried out to further understand the anchoring of these ions within the membrane matrix and their role in boosting the charge of the membrane and, therefore, their electrochemical properties. The study delved into the utilization of GO membranes as monovalent-selective membranes, an approach to boost reverse electrodialysis power densities. The membranes demonstrated impressive selectivity, overcoming 70 folds for divalent cations over K ⁺ .