Plant‐Stem‐Inspired Core–Shell Janus Hydrogel Evaporator for Synergistic Solar Desalination and Hydrovoltaic Generation

Solar‐driven interfacial evaporation is a promising solution to freshwater scarcity, yet it faces bottlenecks regarding salt accumulation, limited evaporation modes, and single functionality. Here, inspired by plant vascular tissues, we have developed a 3D core–shell Janus hydrogel evaporator to achieve the synergy of high‐efficiency freshwater production and stable hydrovoltaic energy harvesting. To construct this core–shell architecture, an alkali‐induced dehydroflurination strategy is employed to solve the bonding challenge between hydrophobic poly(vinylidene fluoride) (PVDF) and the hydrophilic sodium alginate (SA) core, while simultaneously triggering the in situ oxidation of manganese ions to form MnO 2 , thus conferring antibacterial activity on the device. The PVA/chitosan shell and sodium alginate core are endowed with bio‐inspired vascular channels through a foaming and freeze‐thawing process, which ensures efficient water transport and salt resistance. Crucially, this design leverages the tunable water‐content environment within the hydrogel and the water‐polymer interactions to enable a unique “Hydrogel/Janus dual‐core” evaporation mechanism. Furthermore, the incorporation of dodecasodium phytate markedly enhances the surface charge density, yielding an evaporation rate of 4.22 kg m − 2 h − 1 under one sun and a sustained output voltage of 825 mV in seawater. This bioinspired all‐in‐one platform offers a pathway from passive solar distillation to active water‐energy synergy.