Achieving Abnormal Evaporation Behavior Using Melanin/Cellulose‐Based Solar Evaporators via Salt Ion Enrichment

Abstract Solar‐driven interfacial evaporation technology has emerged as a promising solution for seawater desalination, offering a potential remedy to the global water crisis. However, its widespread application is hindered by reduced performance in high‐salinity brines and limited evaporator lifetimes. Inspired by natural melanins, amino acid‐doped poly(norepinephrine) nanoparticles (PNE NPs) are developed as photothermal materials, encapsulated in a cellulose‐based aerogel to form a 3D bilayer porous structure with salt ion enrichment effects. The interaction between the enriched ions in the aerogel weakens the hydrogen bonds between water molecules, reducing evaporation enthalpy and enhancing evaporation rates. Under one sun illumination, the evaporator achieves an evaporation rate of 4.06 kg m −2 h −1 in high‐concentration saline, surpassing the rate in pure water (3.51 kg m −2 h −1 ), with the rate increasing further as salt concentration rises. Notably, even the blank control group without photothermal materials shows an evaporation rate of 1.70 kg m −2 h −1 , demonstrating the aerogel's strong intrinsic evaporation performance. The aerogel maintains its performance over five months of immersion in water without significant degradation. This low‐cost, cellulose‐based aerogel offers a promising solution to the issue of evaporation performance degradation in high‐salinity brines, making large‐scale solar desalination a feasible and effective option.