High-flux flowing interfacial water evaporation under multiple heating sources enabled by a biohybrid hydrogel

Interfacial water evaporation holds great promise in clean water production. However, developing the evaporator with a high evaporation rate and excellent antifouling property remains a challenge. In this paper, we designed a polypyrrole-coated bacterial cellulose hydrogel (PPy-BCH) with a low evaporation enthalpy of 1.97 MJ kg −1 . PPy-BCH was used as the absorber of the flowing evaporator driven by solar irradiation and electro-heating. The highest evaporation rate of 1.78 and 5.88 kg m −2 h −1 was obtained in pure water under 1 sun and 70 ℃ heating conditions, respectively. Benefitting from the superior salt-rejecting ability of this structure and the excellent antifouling properties of the hydrogel, the evaporator enabled a stable performance in seawater and industrial wastewater. The electro-heating platform could be replaced by low-temperature waste heat for large-scale application, considering that the amount of low-temperature waste heat below 200 ℃ is vast worldwide. In addition, the life cycle assessment showed that the flowing evaporator driven by waste heat enabled a lower carbon emission than desalination technologies such as reverse osmosis. Finally, we also demonstrated that the waste heat could enhance the evaporation performance of the evaporator under weak solar irradiation, therefore achieving all-weather clean water production. In conclusion, this study provided a novel way to design a high-flux interfacial water evaporator for fast water treatment and clean water production. • Polypyrrole-coated bacterial cellulose hydrogel is proposed as an evaporator. • A low evaporation enthalpy of 1.97 MJ kg-1 was demonstrated. • Evaporator performed high evaporation rate of 1.78 kg m-2 h-1 under 1 sun. • A world-record evaporation rate of 5.88 kg m-2 h-1 was achieved by waste heat. • Waste heat-driven evaporation enabled a lower carbon emission than reverse osmosis.