Phase-change hydrogel-integrated solar evaporator featuring self-adaptive thermal regulation and anti-fouling for sustainable osmotic energy harvesting

The water–energy–food (WEF) nexus is vital for addressing global resource crises, but intersystem trade-offs challenge holistic management. Interfacial evaporation-driven osmotic energy harvesting platforms offer a proactive solution, enabling concurrent freshwater and electricity production via seawater evaporation and high salinity gradients. However, solar energy fluctuations and salt/oil contamination in evaporators undermine water/power output and durability. To tackle these issues, an encased phase-change hydrogel (EPCH) is developed, integrating a phase-change hydrogel (PCH) within a polyurethane sponge matrix with different wetting properties. Its superhydrophobic photothermal layer ensures robust light absorption and photothermal conversion, while embedded phase-change microcapsules store and release latent heat to mitigate solar intermittency. The lateral hydrophilic polydopamine coating promotes rapid ion/water transport and underwater superoleophobicity for effective oily seawater desalination. The introduction of the PCH improves solar energy utilization efficiency by 27%, while the EPCH-coupled reverse electrodialysis (RED) delivers a 146% enhancement in power density relative to the uncoupled configuration. This study presents a refined multi-coupling framework for WEF platform optimization, advancing sustainable resource management through material engineering and system integration. • An encased phase-change hydrogel (EPCH) enables antifouling and self-adaptive thermal regulation for stable solar evaporation. • EPCH-coupled reverse electrodialysis (RED) achieves stable water–energy output in complex environments. • A synergistic water–energy–food platform is realized by integrating EPCH, RED and hydroponics.