Interfacial Photothermal Membrane Distillation for Direct Solar Water Production

Interfacial photothermal evaporation offers a promising and low-carbon footprint solution for combating worldwide water scarcity. However, its global implementation is constrained by the electricity requirement for water feeding and low freshwater yield due to the spatial decoupling nexus between heat and mass transfer. This paper reports a pumpless and efficient in-situ solar water production engineering strategy, which is termed interfacial photothermal membrane distillation (IPMD). It produces vapor by the in-situ evaporation of the spontaneously wicked water from a superhydrophilic photothermal material. Subsequently, the vapor sandwiched between the photothermal material and a permeable membrane is condensed through membrane distillation. A water productivity of 1.09 kg m −2 h −1 together with a solar-to-water efficiency of up to 70.3% are achieved at 1 sun illumination. Further evidence demonstrates that the driving factors in favor of the IPMD configuration are the interplay between the heat and water in the evaporation interface and the vapor gap. The IPMD device achieves a water yield of 3.62 kg m −2 over 10 h outdoor operation and a salt rejection rate of 98.34%. This work paves a promising way for sustainable freshwater harvesting in remote or off-grid areas.