Enhancing Surface Charge Density of Graphene Oxide Membranes through Al(OH)4− Anion Incorporation for Osmotic Energy Conversion

• Published in: Advanced energy and sustainability research Vol. 5; no. 9
• Main Authors: Aixalà‐Perelló, Anna, Raffone, Federico, Baudino, Luisa, Pedico, Alessandro, Serrapede, Mara, Cicero, Giancarlo, Lamberti, Andrea
• Format: Journal Article
• Language: English
• Published: Wiley-VCH 01-09-2024
• Subjects: 2D materials; blue energy; graphene; ion separation; ion‐exchange membranes
• ISSN: 2699-9412; 2699-9412
• DOI: 10.1002/aesr.202400090

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.
Graphene oxide (GO) is promising for ion exchange membranes due to its surface charge and its nanochannels dimension. However, achieving high ion selectivity and low resistance is challenging. Incorporating Al(OH)4− anions into GO membranes enhances negative surface charge, improving permselectivity, and reducing resistance. This modification boosts reverse electrodialysis power densities, offering potential for efficient energy conversion.