Bifunctional Device for Osmotic Energy Conversion and Photothermal Water Evaporation Enabled by Synergy of Salinity and Pressure Gradients with Thermal Assistance

Osmotic energy conversion and interfacial solar-thermal evaporation possess superiority in obtaining sustainable electricity and freshwater. Previous research has focused on single-function performance enhancement. In this study, an integrated bifunctional device is proposed for osmotic energy conversion and photothermal water evaporation, wherein energy conversion enhancement is realized by the synergetic driving of salinity and pressure gradients, as well as the promoted ion selectivity brought by thermal regulation. The integrated device generates clean water on the evaporation surface as a secondary product with an evaporation rate of 0.88 kg·m–2·h–1. In the integrated device, the "reversed" ionic Soret effect, which induces ion transport from the low-temperature to high-temperature side, is generated by thermal regulation because of the thermal selectivity enhancement effect. The osmotic power density reached 4.50 W·m–2. Finite element simulations clarify that this integrated device improves osmotic power density by enhancing ion diffusion and fluid convection in membrane nanochannels.