High-performance ferroferric oxide nanocomposite hydrogel for integrated evaporative desalination-crop irrigation bifunctional system toward scalable seawater agriculture

Solar-driven interfacial evaporation offers significant potential for clean water production and sustainable agriculture, particularly in regions facing freshwater scarcity and soil salinization. However, integrating solar desalination with crop irrigation to enable scalable seawater utilization remains a major challenge. Here, we report a bifunctional system that integrates solar evaporative desalination-crop irrigation, enabled by high-performance ferroferric oxide-PVA-chitosan nanocomposite hydrogel (FPCH) evaporators. By constructing a hydrated network rich in hydrophilic groups, the FPCH achieves an extraordinarily high evaporation rate of 5.17 kg m⁻² h⁻¹ and energy efficiency of 93.2 % under one-sun illumination, ranking it among the state-of-the-art solar evaporative materials. Notably, the evaporator demonstrates excellent stability and adaptability under complex water conditions, achieving over 99.9 % desalination efficiency across a range of simulated salinities, along with effective removal of organic dyes and heavy metal ions. We further integrated interfacial evaporation, crop irrigation, and solar power into a self-sustained FPCH-based system that delivers 7.5 L m⁻² day⁻¹ of freshwater and enhances crop growth, yielding a 12 cm higher average plant height after 15 days. This work presents a scalable pathway for smart seawater-based agricultural systems in coastal and arid regions, providing potential solutions to address food and water security challenges.