Ultrahigh efficiency solar evaporation through orchestrated multiphase flow.

Abstract

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.