Synergistic modulation of surface and spatial charges in 3D chitosan/2D MoS2 heterogeneous nanofluidics for high-efficiency osmotic energy conversion

Abstract

The transition to a sustainable energy critically depends on efficient technologies for harvesting renewable energy sources. Nanofluidics reverse electrodialysis technique has emerged as a promising platform for directly converting osmotic energy into electricity, a process fundamentally constrained by the trade-off between ion selectivity and permeability. Here, we report a heterogeneous nanofluidic membrane composed of a porous three-dimensional network of quaternized chitosan (QCS) and a two-dimensional (2D) molybdenum disulfide (MoS2) layer. The core of our strategy lies in the coordinated construction of asymmetric ion transport channels by adjusting the surface charge density of the 2D MoS2 and the spatial charge density of the 3D chitosan membrane network. This customized structure significantly enhances ion transport controlled by charge, achieving high selectivity of up to 0.9, while also improving ion transport efficiency and permeability.Therefore, this heterogeneous nanofluidic membrane achieves an output power density of 31.3 W/m2 and a conversion efficiency of 41.3% in salt lake/river water systems. The generated electrical energy successfully powers electronic devices. Both experimental and theoretical calculations confirm that the synergistic effect between the two-dimensional surface charge and the three-dimensional spatial charge plays a crucial role in regulating the selective ion diffusion, thereby synergistically promoting excellent energy conversion performance.