Mushroom-like Graphene Nanosheets/Copper Sulfide Nanowires Foam with Janus-Type Wettability for Solar Steam Generation

Solar steam generation provides an efficient, sustainable, and affordable strategy for freshwater extraction from seawater and wastewater to effectively deal with the water shortage crisis. However, it still faces poor durability because the salting-out effect always leads to a decrease in the evaporation rate at high salt concentrations. To address this issue, we designed mushroom-like micro/nanostructured graphene nanosheets/copper sulfide nanowires (graphene/Cu₇S₄) on Cu foam with Janus-type wettability by in situ oxidation of Cu foam and precipitation conversion, followed by the dip-coating method. The superhydrophilic Cu₇S₄nanowires are endowed with the function of water supply and thermal insulation, and the hydrophobic graphene nanosheets are granted with the function of light absorption and water evaporation. Under one sun illumination, the graphene/Cu₇S₄foam with Janus-type wettability exhibits a high water evaporation rate of up to 2.78 kg m^-2h^-1and long-term stability for brine evaporation. The excellent performances are ascribed to a fast water supply and a salt-rejecting effect due to the capillarity forces and high porosity. This solar steam generation with the Janus-type wettability has broadened the potential applications of seawater desalination, wastewater purification, and sterilization.