Sodium Alginate/TiO<sub>2</sub> Bilayer Material Multiphase\nPhotocatalytic Degradation of Seawater Pollutants and Synergistic\nSeawater Evaporation

Solar Interfacial Evaporation (SIE), which relies solely\non solar\nenergy, reduces heat loss by concentrating heat at the water–air\ninterface, making it an ideal approach for solar-driven seawater desalination\nand wastewater purification. Recently, biomass-based carbon materials\nhave become prominent SIE materials for seawater desalination due\nto their abundant sources, excellent thermal stability, high specific\nsurface area, and rich internal pore structures. In this work, a porous\ncomposite material was developed by cross-linking alginate and cellulose\nwith calcium chloride, followed by loading TiO<sub>2</sub> onto the\nmaterial’s surface to create a composite with a hydrophilic\ntransport layer and a hydrophobic evaporation layer (SAC/CTi). This\nmaterial enables efficient water recovery via solar evaporation of\nseawater and wastewater purification through a three-phase photocatalysis.\nUnder 0.25 W/cm<sup>2</sup> illumination, the surface temperature\nof the sample can reach 192 °C within 3 min. During light-induced\nevaporation, the layered structure retains water between the hydrophilic\ntransport and hydrophobic layers, balancing the water supply and evaporation.\nThe spherical design of the evaporator maintains a high photothermal\nconversion efficiency from different angles. When light is incident\nvertically, the evaporator achieves a peak seawater evaporation rate\nof 1.7 kg/(m<sup>2</sup>·h). Additionally, the double-layer evaporator\ndemonstrates a strong photocatalytic performance, acid–base\nresistance, and effective pollutant purification while evaporating\nseawater. SAC/CTi holds significant potential for applications in\nseawater desalination, water pollution treatment, and broader environmental\nremediation processes.