TiN Nanoparticles-Sodium Alginate Sponge Evaporator with Broadband Light Absorption for Efficient Solar Steam Generation

The development of evaporators with efficient light absorption and rapid water transport is crucial for high-performance solar-driven water evaporation. In this work, a three-dimensional (3D) evaporator based on titanium nitride-sodium alginate (TiN-SA) nanomaterials was fabricated, which exhibited excellent solar absorption and water transport capabilities for highly efficient solar steam generation. Plasmonic TiN nanoparticles were first combined with SA via the coordination of carboxyl groups to form a photothermal nanomaterial, which demonstrates high dispersibility and high photothermal conversion efficiency. The TiN-SA nanomaterial was then uniformly and firmly immobilized into a porous sponge using CaCl2 as a cross-linking agent. The SA can not only improve the dispersibility and light absorption but also enable strong cross-linking with Ca2+ for the improved stability. The resulting 3D evaporator achieved a solar absorption efficiency of 94.61%, attributed to the intrinsic plasmonic resonance of TiN and the enhanced light trapping enabled by multiple reflections within the porous structure. Furthermore, the TiN-SA-sponge evaporator exhibited outstanding photothermal conversion and rapid water transport. Under 1-sun irradiation, it attained a stable evaporation rate of 3.32 kg·m–2·h–1 and a solar-to-vapor conversion efficiency of 94.71%. The evaporator also maintained stable performance across a broad range of pH conditions and in high-salinity environments (up to 25 wt % NaCl). Its effectiveness in treating seawater with good salt resistance and pollutant water demonstrated a strong potential for practical applications in freshwater generation and wastewater treatment. Outdoor testing confirmed a daily drinkable water yield of 31.84 kg·m–2, surpassing many previously reported evaporators based on TiN-based evaporators. This study provides a feasible strategy for designing efficient and robust evaporators for sustainable solar-driven water purification.