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Abstract Solar evaporation has attracted lots of attention recently due to its environmental‐friendly and high efficiency, which is a promising approach for water harvesting. Yet system‐level design has been largely overlooked, limiting its water collection efficiency. Here, a passive water collection device integrating hybrid directional solar heating is presented and radiative cooling within a V‐shaped structure to enhance interior natural convection and reduce heat & mass transfer resistance. Photonics and interface engineering enable selective solar heating, and low evaporation enthalpy with a high‐water supply rate to improve water evaporation, passive daytime radiative cooling, and a superhydrophilic asymmetric channel for efficient condensation and droplet shedding. This design shows an indoor water collection rate of 2.62 kg m −2 h −1 under one sun (1000 W m −2 ) and an outdoor water collection rate of up to 2.76 kg m −2 h −1 under 715 W m −2 . These results indicated the substantial potential of a completely passive water collection system to improve heat and mass transfer behaviors via natural convection, thereby contributing to the mitigation of water scarcity.
Chen et al. (Wed,) studied this question.