Abstract
Harvesting energy from seawater and river water salinity gradients using nanochannel membranes has emerged as a promising strategy for sustainable power generation. Two-dimensional (2D) membrane with porous structures is particularly attractive for this application because they provide a short ionic pathway, promote ion diffusion, and enhance ion flux. However, 2D nanoporous membranes still face a trade-off between ion selectivity and ion flux, which limits the energy conversion efficiency. Accordingly, this study performed COMSOL Multiphysics simulations based on the coupled Poisson–Nernst–Planck and Navier–Stokes equations to optimize the geometric design of a nanoporous membrane. The optimized membrane structure increased the power output by nearly 48.9 % compared to the 2D nanoporous membrane and by approximately 68.2 % relative to the conventional 2D membrane, with the superior performance resulting mainly from an improved ion flux. However, the trade-off with a reduced ion selectivity remained. Accordingly, further simulations were performed to examine the synergistic coupling of the space and surface charges and their effect on enhancing both the ion flux and the selectivity. The results showed that the synergistic effect in best-performing nanochannel configuration design, with an interlayer distance of 2
and a pore size of 0.8
achieved an output power approximately 3-fold that of a 2D nanoporous membrane governed by surface charge effects. Overall, the present findings suggest a promising design route for high-performance membranes capable of scalable and efficient osmotic energy harvesting applications.