Photothermally responsive hydrogel networks induce a dynamic water interface for self-descaling and anomalous evaporation

Solar-driven seawater desalination is an efficient and environmentally friendly technology that directly utilizes renewable energy to produce fresh water. However, salt accumulation and low efficiency of seawater evaporation seriously restrict the long-term stable operation and development of this technology. Herein, a self-cleaning desalination evaporator (SCDE) with a vertical porous structure was obtained by surface modification of thermosensitive hydrogels with photothermal materials and directional freeze drying. The functional groups within the evaporator selectively capture and enrich multivalent ions from seawater at the interface. This local ion accumulation disrupts the hydrogen bonding network, thereby lowering the enthalpy of vaporization and enhancing the evaporation rate. The evaporation rate of the SCDE in brine reached 3.22 kg m⁻² h⁻¹ under 1 sun irradiation, surpassing the rate of 2.21 kg m⁻² h⁻¹ in pure water, exhibiting anomalous evaporation behavior. Furthermore, the photothermal-responsive hydrogel network induces dynamic modulation of the vertical channel water interface, enabling the SCDE to achieve self-cleaning desalination functionality. The reversible phase transition of SCDE enables water to flush through the vertical channels, preventing salt accumulation within the channels. This work offers a new approach to the design of high-performance, self-cleaning desalination evaporators for desalination.