Multifunctional composite membranes for interfacial solar steam and electricity generation

Emerging water purification technology, known as interfacial solar steam generation (ISSG), has been rapidly developing in recent years. ISSG offers a promising solution to address both freshwater shortage and energy demand by simultaneously producing freshwater and electricity. This is achieved through the combination of microporous films and highly efficient photothermal materials. In this study, we have developed a composite film using a 2D material, reduced graphene oxide (rGO), and a combination of 1D materials, chitin fiber@multiwalled carbon nanotube (Chiber@CNT). Through a hybrid dimensional design, these materials' advantages are integrated, resulting in a composite film with a distinct laminar porous structure and excellent broadband absorption. Notably, under 1 kW center dot m(-2) sunlight irradiation, the composite film achieves a water evaporation flux of 2.10 kg center dot m(-2)center dot h(-1) with a photothermal conversion efficiency of 75.79%. In addition, by utilizing an energy-harvesting strategy based on natural water evaporation in porous nanomaterials for power generation, the composite film successfully enables the simultaneous production of freshwater and electricity. Its output voltage reaches 0.39 V in a 3.5 wt% NaCl solution. Furthermore, the film's output voltage varies with the concentration of NaCl, increasing from 0.26 V (in deionized water) to 0.45 V (in the saturated NaCl solution). Molecular dynamic simulation results indicate that the enhanced power generation can be attributed to the difference in interatomic interaction strength between ions and hydrophilic functional groups in chitin fiber (Chiber). This finding provides a deep physical mechanism and opens up possibilities for the film's application in highly concentrated salt solutions.