Enhancing salt resistance and all-day efficient solar interfacial evaporation of antibacterial sodium alginate-based porous hydrogels via surface patterning

Abstract

The fully bio-based solar-driven interfacial evaporator offers the advantage of being environmentally friendly, but achieving efficient evaporation throughout the day, good salt resistance, and excellent antibacterial properties remains a significant challenge. In this study, a fully bio-based porous hydrogel with a core-shell structure was prepared using sodium alginate (SA) as the matrix and pulp fiber (PF) as the reinforcing material. Crosslinking SA with Cu²⁺ ions imparts excellent antibacterial properties to the evaporator. In the hydrogel core, SA forms vertically aligned lamellar pore structures, with PF providing support between the layers, which gives the evaporator good mechanical properties, water transport capacity, and thermal insulation performance. The dense surface layer formed by SA contains CuS nanoparticles, resulting in high photothermal conversion efficiency. A trapezoidal pattern constructed on the surface enhances the evaporation rate by 14 % and improves salt resistance through the Marangoni effect, enabling the evaporator to maintain an evaporation rate of 2.42 kg m⁻² h⁻¹ in a 15 wt% saline solution. Additionally, the trapezoidal pattern increases the evaporation rate by 37.5 % at low incident angles, achieving efficient all-day evaporation. The prepared hydrogel shows great potential for seawater desalination applications.