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 low‐temperature 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−1 K−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−2 h−1), surpassing the‐state‐of‐the‐art solar evaporators, and presents good anti‐acid/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. Super‐hydrophilic, self‐floating N,O dual‐doped carbon foam (NCF) is facilely fabricated through controlled carbonization of PET waste at 340 °C. NCF possesses rich N,O‐containing groups, ultra‐low thermal conductivity, 3D interconnected pores, and low water evaporation enthalpy. Therefore, NCF exhibits excellent performance in interfacial solar evaporation, e.g., high evaporation rate of 2.4 kg m−2 h−1, good anti‐acid/basic abilities, long‐term salt‐resistance, and self‐cleaning.