Internal interface engineering in single-component hydrogels for interfacial solar evaporation

Abstract

Global water scarcity demands sustainable and high-efficiency freshwater production technologies. Interfacial solar evaporation (ISE) has emerged as a promising strategy; however, its broader application remains limited due to suboptimal evaporation rates, interfacial incompatibility among components, and performance degradation in complex wastewater environments. In this work, we introduce a single-component amphiphilic tetra-gel evaporator synthesized via a facile, efficient thiol-ene ‘click’ reaction between 4-arm polyethylene glycol thiol (tetra-PEG-SH) with α,ω-alkene-terminated poly(3-hexylthiophene) (alkene-P3HT-alkene). The resulting hydrogel undergoes spontaneous microscale phase separation, forming interwoven hydrophilic PEG and hydrophobic P3HT domains, which create dynamic internal air–water interfaces within the evaporator. Born–Oppenheimer molecular dynamics simulations confirm preferential hydration of PEG segments and persistent amphiphilic segregation, shedding light on the mechanism of internal interface formation. Under one-sun irradiation, the PEG-P3HT-based 2D evaporator achieves an exceptional evaporation rate of 6.24 kg m⁻² h⁻¹, attributed to the enlarged and accessible internal evaporative surface. Moreover, it maintains high performance when treating challenging wastewater sources including lake sewage, oily wastewater, and laundry effluent. With its additive-free composition, salt-resilient structure, and consistent multi-cycle operation, PEG-P3HT presents a robust and innovative interfacial engineering platform for efficient solar-driven water purification.