Molecular self-assembled cellulose enabling durable, scalable, high-power osmotic energy harvesting

In recent years, renewable cellulose-based ion exchange membranes have emerged as promising candidates for capturing green, abundant osmotic energy. However, the low power density and structural/performance instability are challenging for such cellulose membranes. Herein, cellulose-molecule self-assembly engineering (CMA) is developed to construct environmentally friendly, durable, scalable cellulose membranes (CMA membranes). Such a strategy enables CMA membranes with ideal nanochannels (∼7 nm) and tailored channel lengths, which support excellent ion selectivity and ion fluxes toward high-performance osmotic energy harvesting. Finite element simulations also verified the function of tailored nanochannel length on osmotic energy conversion. Correspondingly, our CMA membrane shows a high-power density of 2.27 W/m² at a 50-fold KCl gradient and super high voltage of 1.32 V with 30-pair CMA membranes (testing area of 22.2 cm²). In addition, the CMA membrane demonstrates long-term structural and dimensional integrity in saline solution, due to their high wet strength (4.2 MPa for N-CMA membrane and 0.5 MPa for P-CMA membrane), and correspondingly generates ultrastable yet high power density more than 100 days. The self-assembly engineering of cellulose molecules constructs high-performance ion-selective membranes with environmentally friendly, scalable, high wet strength and stability advantages, which guide sustainable nanofluidic applications beyond the blue energy.