Strategy of bilayer structure of cellulose-based membrane with an efficient anti-fouling for solar-driver seawater desalination

Abstract

Freshwater scarcity, insufficient heat localization, and membrane fouling remain major challenges for interfacial solar steam generation and seawater desalination. Conventional single-layer membranes often struggle to balance light absorption, heat management, and antifouling performance. To overcome these limitations, a novel bilayer composite membrane has been developed, consisting of a hydrophilic CuO-cellulose membrane layer (M-RC/CuO) and a hydrophobic carbonized CuO-cellulose membrane layer (h-CC/CuO), designed for efficient and sustainable ISSG. The M-RC/CuO membrane layer was prepared via solution casting in a DMAc/LiCl system with CuO doping, while the h-CC/CuO membrane layer was obtained through oxidative carbonization, forming a flower-like CuO morphology and a layered carbon structure. Under one sun irradiation, the M-RC@h-CC evaporator achieved a high evaporation rate of 1.85 kg·m⁻²·h⁻¹ and a photothermal conversion efficiency exceeding 91.23%, outperforming the single-layer M-RC/CuO (1.74 kg·m⁻²·h⁻¹, 86.5%) and h-CC/CuO membranes (1.32 kg·m⁻²·h⁻¹, 71.8%). Additionally, the bilayer structure effectively minimized heat losses via conduction, convection, and radiation, a performance enhancement attributed to the hierarchical porous network and optimized CuO distribution in the M-RC/CuO layer together with the heat confinement and antifouling function of the h-CC/CuO layer. The composite membrane also exhibited excellent resistance to fouling caused by organic dyes such as Organic pollutants HA, methylene blue and methyl orange, with dye adsorption maintained below 25%. These results indicate that the bilayer structural design, rather than a single parameter such as CuO loading, plays the dominant role in achieving high evaporation efficiency and antifouling durability. This bilayer design presents a promising strategy for developing high-performance, scalable, and antifouling ISSG systems for water purification applications.