Self-Floating Efficient Solar Steam Generators Constructed Using Super-Hydrophilic N,O Dual-Doped Carbon Foams from Waste Polyester

Solar evaporation is recognized as a prospective technique to produce freshwater from non-drinkable water using inexhaustible solar energy.However, it remains a challenge to fabricate low-cost solar evaporators with obviously reduced water evaporation enthalpy to achieve high evaporation rates. Herein, N,O dual-doped carbon foam（NCF） is fabricated from the lowtemperature carbonization of poly（ethylene terephthalate）(PET) waste by melamine/molten salts at 340 °C. During carbonization, melamine reacts with carboxylic acids of PET degradation products to yield a crosslinking network, and then molten salts catalyze the decarboxylation and dehydration to construct a stable framework. Owing to rich N,O-containing groups, 3D interconnected pores, super-hydrophilicity, and ultra-low thermal conductivity(0.0599 W m-1K-1), NCF not only achieves high light absorbance（ca. 99%） and solar-to-thermal conversion, but also promotes the formation of water cluster to reduce water evaporation enthalpy by ca. 37%.Consequently, NCF exhibits a high evaporation rate(2.4 kg m-2h-1),surpassing the-state-of-the-art solar evaporators, and presents good antiacid/basic abilities, long-term salt-resistance, and self-cleaning ability.Importantly, a large-scale NCF-based outdoor solar desalination device is developed to produce freshwater. The daily freshwater production amount per unit area（6.3 kg） meets the two adults' daily water consumption. The trash-to-treasure strategy will give impetus to the development of low-cost,advanced solar evaporators from waste plastics for addressing the global freshwater shortage.