Jellyfish–mimetic solar evaporator with polyelectrolyte skeleton for sustainable desalination under higher salinity

Abstract

Photothermal membranes have seen significant advancements in the field of solar seawater desalination. However, their practical application is hindered by solid-salt crystallization, which results in reduced evaporation rates. Herein, an “all–in–one” anionic jellyfish–mimetic solar evaporator is reported with sustainable condensate yields and electrostatic repulsion to prevent solid–salt crystallization. The innovative structure is composed of the jellyfish–mimetic photothermal head (in–situ grown nanospheres of Prussian blue analogue and molybdenum disulfide (PBA@MoS₂)) while polyelectrolyte legs (water channels) enriched with SO₃⁻ groups by polystyrene sodium sulfonate (PSS). The negatively charged evaporator was characterized by a high concentration of SO₃⁻, which induces the Donnan effect by confining Na⁺ to the microchannels. This process reduces the diffusion of salt ions into the water supply layer, thereby addressing the issue of salt deposition at its fundamental level. As a result, a high evaporation rate of 1.89 kg m⁻² h⁻¹ was achieved in high–concentration brine (20 wt% NaCl) under one sun irradiation. More importantly, the evaporator achieves high condensate yields (15.7 g/10 h) under natural sunlight and demonstrates excellent reproducibility in evaporation rates over 20 performance cycles on different days, even with a salinity of 20 wt%. The efficient evaporation efficiency and high salt tolerance present significant practical potential for solar–driven seawater desalination.