Soil-inspired multi-stage heterogeneous nanochannel membranes for enhanced osmotic energy conversion

The nanofluidic ion transporting channels for harvesting blue osmotic energy between river water and seawater have received great attentions recently. However, the design of excellent ion selective nanochannel membranes while retaining high mechanical strength and ion flux remains a challenge. Herein, we present a novel multi-stage heterogeneous nanochannel membranes consisting of alternating TEMPO oxidized cellulose nanofibers (TOCNFs) and MXene layers inspired by the multi-layer structure of natural soil. The ingenious binding of “soft layer” of TOCNFs acting as ion selective layer and “hard layer” of MXene acting as ion permeable/structural support layer contributes to the fast cationic transport through the robust nanochannel membranes. In hypersaline solutions, a remarkable power density of 95.13 W m⁻² is produced. This work provides a new strategy for heterogeneous nanochannel membranes for osmotic energy generation.