Ultra‐High Freshwater Production Via Coupling Photo‐/Electro‐Thermal Self‐Heating and Self‐Insulating Janus Membrane

Abstract Thermally driven membrane distillation (TDMD) has emerged as a promising seawater desalination technology to address the freshwater shortage and energy crisis. However, the conventional “bulk‐heating” technologies results in serious temperature polarization phenomenon, hindering efficient utilization of the energy. Here, an innovative hydroxylated CNTs‐engineered polyvinylidene fluoride (H‐CNT@PVDF) membrane is proposed which imparts an efficient, localized photo‐/electro‐thermal self‐heating effect. To prevent the heat loss from the self‐heating layer to bulk water, a transparent silica aerogel microspheres (SAM) layer is deposited on the H‐CNT layer, achieving excellent self‐insulating effect. The innovative SAM@H‐CNT@PVDF Janus membrane achieves a 486% increase in MD flux compared with the conventional membrane. Although SAM layer only account for 3.8% of the membrane, the thermal resistance increases, unexpectedly, by more than 600%, which allows most of the heat to be concentrated at the H‐CNT layer and used for seawater evaporation. The overall energy‐to‐water efficiency reach 94.5%, outperforming state‐of‐the‐art MD devices. Additionally, the SAM layer demonstrates excellent anti‐electrooxidation effect with the current degradation decreasing from 75.6% to 21.1%, ensuring long‐term working for the membrane. The membrane represents a significant advancement in MD technology and holds substantial promise for ultra‐low energy seawater desalination, offering a promising solution to water‐energy nexus.