High-performance graphene oxide / sodium alginate composite membrane for marine osmotic energy conversion

Abstract

With advancements in Reverse Electrodialysis (RED) technology, an increasing number of high-power-density permeable membranes have been proposed for salinity gradient power generation. Two-dimensional (2D) materials, characterized by their abundant surface charges, can form nanochannels with high surface charge density during the stacking process to achieve exceptional ion selectivity. Additionally, the stacked structure aids in creating a highly porous permeable membrane surface, facilitating substantial ion flux during ion transport. Consequently, permeable membranes composed of 2D materials such as graphene oxide (GO) and MXenes exhibit particularly outstanding performance in the field of salinity gradient power generation. In this context, we designed an ion-selective composite membrane formed by the mixed crosslinking of graphene oxide and sodium alginate. The composite membrane utilizes stacked graphene oxide nanosheets to provide a two-dimensional layered framework, while sodium alginate, rich in negatively charged functional groups, crosslinks between the nanosheets to create abundant spatial charge, significantly enhancing the power density for salinity gradient power generation. This composite membrane exhibits a power density of approximately 14.75 W/m² under a 50-fold NaCl solution salinity gradient, and an astonishing 20.94 W/m² under a 50-fold KCl solution salinity gradient. In real seawater, it also achieves a high power density of 19.39 W/m², far exceeding the industry benchmark of 5.0 W/m² and outperforming most existing materials. These results are expected to promote the practical application of marine salinity gradient energy and provide new design strategies for the development of marine salinity gradient resources.