A Janus biomass-derived photothermal material with low enthalpy of evaporation and high salt tolerance for efficient solar evaporation

Abstract

Solar-driven interfacial evaporation (SDIE) as a promising solution to freshwater scarcity has emerged. In recent years, there have been notable advancements in the research domain of SDIE. Nevertheless, the endeavor to develop biomass-derived solar evaporators that possess environmental compatibility, exhibit high evaporation efficiencies, and demonstrate robust salt resistance continues to pose significant challenges. This work innovatively proposes carbon nanotubes (CNTs) loaded on polydopamine modified butia capitata leaf stem, and hydrophobic surface modification to obtain a Janus biomass-derived solar evaporator (CPLS-J). Molecular dynamics simulations (MDS) at the molecular scale verified that cellulose network of CPLS-J and the introduced 1H,1H,2H,2H-Perfluorooctyltriethoxysilane (POTS) system, which lowered the enthalpy of evaporation in water and substantially enhanced the diffusion coefficient of water molecules, jointly promoted efficient evaporation. The results demonstrate CPLS-J has high evaporation efficiency, high salt resistance and stability, with a full-spectrum solar absorptivity of about 93.9 %, an evaporation efficiency was up to 2.27 kg m^–2 h⁻¹, and a photo-thermal conversion efficiency of 93.63 % at 1 solar radiation, which outperformed most of the biomass-derived evaporators. CPLS-J can be used not only for desalination of seawater but also for purification of various other water sources with excellent purification effect. With the implementation of the green energy strategy, sustainable and efficient biomass-derived solar evaporators can provide a new way to solve the freshwater shortage problem.