Graphite/SnSe hybrid-embedded monolithic foams with hierarchical and bimodal pores for high performance solar desalination membranes with spontaneous salt rejection

Abstract

Solar water evaporation techniques have attracted considerable interest due to their strong potential to disrupt existing desalination systems. As the interfaical solar steam generation has been heavily studied to explore the strategies to increase light absorption, recent effort has been focused on the development of mass transfer-based interfacial layer. Here, we propose monolithic solar evaporator (MSE) having a hierarchical mass transfer layer made of a melamine foam skeleton coated with graphite and tin selenide photothermal materials (G-SnSe). Unlike conventional solar evaporator structures consisting of double or three layers, the MSE has a monolithic configuration on top of wihch G-SnSe forms the bimodal porous structure (50-60% porosity) for enhancing the mass transfer. Due to the reinforced capillarity at the small-scale pores in the bimodal structure, the MSE structure achieves a high evaporation rate of 1.303 kg m-2h- 1 when exposed to 1 sun irradiation. Furthermore, large-scale pores in the bimodal structures would simultaneously promote the autonomous rejection of salts at the MSE surface during solar desalination. We show that optimizing the bimodally porous structure and the interfacial properties significantly improves the solar evaporation efficiency, demonstrating the intricated structure for the next generation solar evaporation and desalination systems.