A sustainable solar steam generator based on natural wool and AlNi-graphene for enhanced photothermal efficiency

Interfacial solar steam generation (ISSG) has emerged as a simple, effective, and sustainable technology for producing potable water from seawater and wastewater. In this study, a cost-effective AlNi material was synthesized using a straightforward hydrothermal method with easily accessible metal salts. The AlNi was then combined with graphene to form an AlNi-Gr composite, which was integrated onto a natural wool (NW) substrate an eco-friendly, biodegradable material with high water absorption and thermal insulation properties resulting in a photothermal material termed AlNi-Gr/NW. This composite leverages the excellent light absorption of graphene and the multiple light scattering within the porous AlNi structure to achieve broad-spectrum solar absorption. As a solar steam generator, AlNi-Gr/NW achieved a high evaporation rate of 3.4 kg m-2 h-1 and 88 % efficiency, owing to the combined effects of AlNi, graphene, and NW's thermal insulation. Moreover, the material maintained high performance not only with pure water but also with saline, acidic, basic, and contaminated waters, achieving up to 93 % removal of salts and heavy metal ions. Under one sun illumination, the surface temperature of AlNi-Gr/NW rapidly reached 67 degrees C within one minute, indicating fast solar-to-thermal energy conversion. These results suggest that AlNi-Gr/NW is a promising, low-cost, and sustainable photothermal material for clean water production and could guide future developments in high-performance solar desalination systems.