2D/3D Hybrid Solar Interfacial Evaporators with High Evaporation Efficiency

The development of photothermal evaporators with efficient photothermal conversion performance and robust chemical stability is essential for achieving long-term, stable solar desalination. This study introduces a 2D/3D hybrid solar interfacial evaporator designed to harvest freshwater from seawater. The device incorporates a sandwich-structured twodimensional (2D) composite film as the photothermal layer. The top and bottom layers consist of green, flexible one-dimensional (1D) cellulose nanofiber (CNF) membranes, while the middle layer is composed of 2D bismuth (Bi) nanosheets, forming a 2D CNF/2D Bi/2D CNF composite film. The 2D Bi nanosheets serve as the photothermal conversion component, and the 1D CNF membranes provide structural flexibility. Additionally, a foam-like polyvinyl alcohol (PVA)-based hydrogel with a three-dimensional (3D) porous structure acts as the water supply layer. This composite evaporator addresses the low evaporation rates typically observed in standalone 2D photothermal membranes while maintaining effective resistance to salt accumulation. Synergistic interactions between the 2D photothermal film and 3D hydrogel drive water evaporation, with the hydrogel playing a pivotal role. Under onesun illumination, the device achieves an evaporation rate exceeding $3.0 \mathrm{~kg} \cdot \mathrm{~m}^{-2} \cdot \mathrm{~h}^{-1}$, demonstrating promising potential for industrial applications.