Less is More: Reducing Evaporation Dead Zones to Tune Thermal Convection in Donut‐Structure Evaporators for High‐Efficiency Interfacial Solar Steam Generation

Abstract Interfacial solar steam generation (ISSG) has emerged as a promising and eco‐friendly desalination technology for producing fresh water from diverse sources, offering a sustainable solution to global water scarcity. However, practical applications face a significant bottleneck: as the evaporation surface area increases, the evaporation rate decreases, limiting large‐scale implementation. In this study, a hydrogel evaporator with a donut‐shaped structure is developed using 3D‐printed molds to address this issue by enhancing thermal convection and reducing evaporation dead zones. Simulations reveal that optimized structural designs improve heat distribution and air convection, leading to a significant improvement in evaporation performance. Experimental results further confirm an impressive evaporation rate of 3.47 kg m ⁻² h ⁻¹ , representing a 66% improvement compared to conventional designs. This work highlights the potential of structural design in hydrogel evaporators to optimize thermal management and enhance evaporation efficiency. By achieving higher evaporation rates while minimizing material usage, this approach provides a scalable strategy for efficient solar desalination.