A 3D-printed hierarchical chimney for high-yield solar evaporation

Abstract

Solar water evaporation can produce water with a low carbon footprint using abundant solar energy, but efficiency and stability are hindered by low evaporation rates and salt accumulation issues. We report a hierarchical solar evaporator made of cellulose acetate and graphene oxide via 3D printing. It features hierarchical structures at three levels: a millimeter-scale chimney-shaped evaporator resembling a chimney effect for directional steam flow, and micro-cells, micro-cavities, and nano-channels that enhance water supply and solar absorption. An evaporation rate of up to 10.2 kg m⁻² h⁻¹ is achieved with simulated natural sunlight. The hierarchical structures suppress salt crystal formation, ensuring long-term stability. In the outdoor experiment under natural sunlight, the fresh water yield of the evaporators from real seawater reaches 95.1 kg m⁻² day⁻¹. The 3D-printed evaporator also demonstrates excellent long-term performance and reusability when treating realistic pharmaceutical wastewater. This study synergizing 3D printing and hierarchical solar evaporators demonstrates an effective solution to the energy–water nexus challenge.