A solar interface evaporator with a “square table” layered structure to reduce heat loss

Solar-driven interfacial evaporation (SDIE) is a technology that employs photothermal materials to convert solar energy into thermal energy, concentrating it at the gas-liquid interface. This process promotes preferential water evaporation at the interface, facilitating effective water purification. This study introduces a novel solar-driven interfacial evaporator featuring an optimized "square table" three-layer configuration, achieving efficient evaporation through the integration of a photothermal conversion layer (Cu/CuO foam), a water transport layer (polyvinyl alcohol (PVA) sponge), and a thermal barrier layer (ethylene-vinyl acetate (EVA) sponge). In this distinctive square table-style structure, the top layer comprises hydrophobic Cu/CuO foam. The middle layer is a super-hydrophilic PVA sponge, uniformly perforated with 3 mm diameter through-holes to significantly increase the active evaporation area. Water transmission channels located on the four sides facilitate water absorption. The EVA sponge bonded beneath the PVA sponge serves as an insulation layer, significantly reducing the heat conduction loss from the evaporator to the bulk water. A 2 × 2 cm PVA absorbent column is located at the center of the EVA sponge to prevent insufficient water supply in the middle of the evaporator. Under one sun illumination, the evaporator achieves an evaporation rate of 1.20 kg m⁻²h⁻¹ with a corresponding photothermal conversion efficiency of 75.3 %. No significant salt accumulation was observed after continuous operation in 10 wt% brine for 10 h, demonstrating excellent salt tolerance and evaporation stability. This design presents a promising approach to minimizing heat loss in solar interfacial evaporators.