Introduction of Low Dimensional Charge-Boosters into Graphene Oxide Nanochannels for Energy Harvesting

Osmotic energy, a potential source of electricity from salinity differences in water, relies on ion-exchange membranes to convert salt gradient energy into electric power. However, these membranes encounter challenges, including inadequate charge densities and resistance to mass transfer. Recent efforts have focused on enhancing ion-selective membranes using materials like polymers, metal oxides, and frameworks. Two-dimensional (2D) nanosheets, such as graphene and boron nitride, have shown promise, featuring nanochannels with controlled thickness. These structures exhibit an electrical double layer that enhances ion transport. Utilizing reverse electrodialysis (RED), 2D nanochannel membranes demonstrate high ion conductance and osmotic power extraction. However, the challenges also arise from the intrinsic limitations of 2D nanomaterials, including relatively low surface charge densities and mass-transfer resistance, which hinder their effective integration into RED systems. In this study, we used negatively charged graphene quantum dots (GQDs) and polyelectrolyte nanorods to boost the charge density of graphene oxide (GO) nanochannels. Charged GQDs and polyelectrolyte nanorods can be integrated into GO fibers and films to increase the charge density and improve energy harvesting performances. Moreover, by aligning nanoscale charge boosters onto GO nanochannels through a blade-coating technique, the charge density can be precisely directed to optimize ion transport. Our study introduces an innovative and efficient approach to refining ion transport characteristics of 2D GO nanochannels, ultimately enhancing ion selectivity for proficient osmotic energy generation.