Nanoporous fibrous 3D solar evaporator for efficient freshwater generation and salt recovery

Solar-driven interfacial evaporators (SDIEs) have advanced sustainable desalination by enabling freshwater production and salt harvesting from brines. Here, electrospun cellulose acetate (CA) films with aligned nanoporous fibers are rolled into a 3D cylinder and partially coated with a carbon black/poly(vinyl alcohol) (CB/PVA) photothermal layer to create an environmentally-friendly SDIE for concurrent desalination and salt recovery. The evaporator achieves a high evaporation rate of 4.44 kg m −2 h −1 under 1 sun, corresponding to a photothermal conversion efficiency of 107.3% based on equivalent evaporation enthalpy. This performance is ascribed to reduced vaporization enthalpy from material-water interactions and nanoporous structures, along with cold evaporation-induced environmental energy harvesting. Under 1 sun, the SDIE stably treats brines of 3.5–20 wt% salinity with edge-preferential salt crystallization due to its fibrous microporous architecture. This feature allows gravity-assisted salt collection and durable function in 10 wt% NaCl for 10 days, maintaining average steam generation and salt harvesting rates of 4.71 kg m −2 h −1 and 3.21 kg m −2 day −1 , respectively. Condensed waters from 3.5 wt% NaCl and simulated seawater exhibit high purity with significantly lower conductivities. The outdoor experiment also reveals the stable performance of the SDIE under actual conditions. Computational fluid dynamics (CFD) simulation further validates edge-preferential salt aggregation. This innovative device offers a promising route for simultaneous freshwater and salt collection from brines.