Ultrahigh efficiency solar evaporation through orchestrated multiphase flow

Solar-driven interfacial evaporation (SDIE) represents a sustainable solution to alleviate global water scarcity. While holding great promise, developing energy-efficient and salt-resistant systems remains a critical challenge. Here, we address this issue by establishing a multiphase-flow dynamics framework that couples water replenishment, vapor dissipation, salt rejection, and heat transfer. An integrated evaporation system is designed using bimodal porous polyvinyl alcohol–polyvinyl pyrrolidone hydrogels for synchronized water supply and salt reflux, perforated Juncus effusus stems to facilitate vapor generation and escape, and flat-band λ-Ti3O5 powders for broadband solar absorption. Under one-sun irradiation, the system achieves an exceptional evaporation rate of 11.2 kg m−2 h−1 (normalized to the top-illumination projected area) and an apparent efficiency of 278.3% (defined as the ratio of total energy gain from incident solar irradiation and environmental heat harvesting to solar input). Notably, it operates stably in ~15 wt.% saline water without salt crystallization. Outdoor tests under natural sunlight yield a daily freshwater production of 39.8 L m−2 (normalized to the top-illumination projected area). This work presents a robust and scalable approach to sustained solar desalination by resolving energy, water, vapor, and salt management in SDIE systems. A multiphase-flow-guided solar evaporator integrates water replenishment, vapor dissipation, salt reflux, and heat management, enabling ultrahigh-efficiency solar desalination with stable operation in ~15 wt.% saline water and high daily freshwater production under natural sunlight.