Ultrathin Photothermal Membranes with Heat and Flow Micro-Highways for Enhanced Solar Evaporation

The global freshwater crisis has driven the development of solar-driven water evaporation. Efficient solar-driven water evaporation requires both effective heat localization and continuous water supply at the evaporation interface, which remain challenging due to disordered thermal pathways and inefficient fluid transport. Herein, an ultrathin (≈130 µm), flexible polyurethane (TPU) membrane integrated with dual transport pathways is reported for water transport and heat conduction, enabling synergistic thermal management and hydration. The membrane is embedded with vertically aligned MoS₂ nanoflowers and graphene nanoplatelets (GNPs), and through-plane micro-channels by a classic non-solvent-induced phase separation strategy. GNPs serve as thermal conductive bridges, promoting through-plane heat transfer and guiding the orientation of MoS₂. Despite the modest filler content (10 wt.%), the optimized membrane exhibits broadband solar absorption (94.3%), high photothermal conversion efficiency (96.1%), and a 2.5-fold increase in through-plane thermal conductivity compared to GNP-free membranes. Upon surface hydrophilic modification, the membrane achieves a solar evaporation rate of 2.62 kg·m^-2·h^-1 under one sun, with an energy conversion efficiency of 93.5%, attributable to a sharp reduction in total heat loss from 9.1% to 2%. This work highlights a material- and architecture-driven strategy for constructing efficient photothermal membranes, paving ways for high-performance and portable solar water evaporators.