Synergy of photothermal effect in integrated 0D natural melanin /2D reduced graphene oxide for effective solar steam generation and water purification

Solar steam generation has attracted widespread attention due to its ability to produce clean water without conventional energy consumption. However, how to obtain an environment-friendly, sustainable and powerful solar absorber system to generate efficient steam is still challenged. The melanin nanoparticles can dissipate 99.9% of the absorbed UV and visible without radiation, and their spherical nanostructure can effectively preserve heat. In addition, the oxygen and nitrogen related functional groups on their surfaces further reduce thermal conductivity. Thus, in this work, a new system of photothermal aerogel composed of sodium alginate (SA) with heterostructures absorber of natural 0D melanin nanoparticles (MNP) synergistic 2D reduced graphene oxide (rGO) was developed for solar-steam generation. By optimizing the porosity and preparation method, the alginate-based aerogels showed excellent absorption and lower reflection through the whole sunlight spectrum (200–2500 nm), super hydrophilicity, and lower thermal conductivity (0.05281 w k⁻¹ T⁻¹). The average evaporation rate and solar-steam generation efficiency reached 2.64 Kg m⁻² h⁻¹ and 93.9%, respectively, under one-sun illumination. Meanwhile, the solar driven evaporator exhibited excellent ability to purify realistic waters, such as seawater, ionized wastewater and dyeing sewage with ～ 100% removal rate. Significantly, this strategy offers a novel heterostructures absorber to construct a powerful solar water evaporation system for high-efficiency vapor generation and water purification in practical applications.