Silica-reinforced tannin-carbon black/sodium alginate hydrogel on melamine foam for mechanically robust and salt-resistant solar interfacial evaporation

Solar-driven desalination provides a sustainable approach to address global freshwater scarcity, yet its application is significantly hindered by mechanical instability and salt accumulation issues in conventional evaporators. Here, we report a mechanically robust, salt-resistant, and highly efficient three-dimensional hydrogel evaporator (TF/CB@SA/MF-SiO 2 ) that integrates tannic acid-Fe 3+ complexes (TF), carbon black (CB), SiO 2 nanoparticles, and sodium alginate (SA) within a porous melamine foam (MF) scaffold. The CB and TF components provide broadband (>97 %) light absorption from 250 to 2500 nm, while the in situ-formed SA-SiO 2 hydrogel network reinforces the composite structure through strong interfacial bonding, restricting polymer chain mobility and improving compressive strength and elasticity. Under standard one-sun irradiation, the evaporator maintains a high evaporation rate of 2.06 kg m −2  h −1 and demonstrates remarkable long-term stability even under high salinity conditions (up to 20 wt% NaCl). Mechanical testing reveals that the combined CB-SiO 2 reinforcement yields minimal deformation and superior recovery. Practical outdoor tests confirm the evaporator's reliability, yielding freshwater meeting WHO drinking water standards. This multifunctional evaporator demonstrates long-term durability and high salt rejection, providing a viable pathway toward scalable, off-grid desalination and wastewater purification.