Exploring Ion Transmission Mechanisms in Clay-Based 2D Nanofluidics for Osmotic Energy Conversion

Clay-based 2D nanofluidics present a promising avenue for osmotic energy harvesting due to their low cost and straightforward large-scale preparation. However, a comprehensive understanding of ion transport mechanisms, and horizontal and vertical transmission, remains incomplete. By employing a multiscale approach in combination of first-principles calculations and molecular dynamics simulations, the issue of how transmission directions impact on the clay-based 2D nanofluidics on osmotic energy conversion is addressed. It is indicated that the selective and rapid hopping transport of cations in clay-based 2D nanofluidics is facilitated by the electrostatic field within charged nanochannels. Furthermore, horizontally transported nanofluidics exhibited stronger ion fluxes, higher ion transport efficiencies, and lower transmembrane energy barriers compared to vertically transported ones. Therefore, adjusting the ion transport pathways between artificial seawater and river water resulted in an increase in osmotic power output from 2.8 to 5.3 W m^-2, surpassing the commercial benchmark (5 W m^-2). This work enhanced the understanding of ion transport pathways in clay-based 2D nanofluidics, advancing the practical applications of osmotic energy harvesting.