Janus-structured lignin hydrogel evaporator via laser direct writing for high efficiency seawater desalination and solar power generation

Interfacial solar steam generation offers an eco-friendly and energy-efficient method for clean water production. Among various interfacial evaporator materials, lignin hydrogels are considered as one of the most promising candidates for interfacial solar steam generator due to the renewability and biocompatibility of lignin. In this work, laser direct-writing technology is employed to tailor hydrophobic and hydrophilic properties of the top and bottom surfaces of the lignin hydrogel. A series of lignin hydrogels with different content of lignin (LPSMA-x, x presents the lignin content) were prepared. Among them, LPSMA-1.5 shows an excellent evaporation rate of 2.16 kg m −2  h −1 under one sun illumination, and can almost completely remove organic pollutants and more than 99 % of major ions in the desalination test of actual Bohai seawater, meeting WHO drinking water standards. Additionally, LPSMA-1.5 can generate an open-circuit voltage and short-circuit current of approximately 600 mV and 80 mA in seawater under one sun illumination. LPSMA-1.5 also demonstrates high antibacterial efficiency (99.9 % inhibition against E. coli and 90.6 % against environmental mixed microorganisms). Laser induced graphene Janus-structured hydrogel interfacial evaporator by laser direct writing fabrication has great potential in desalination and wastewater treatment applications because of the cost effectiveness, high performance, and multi-functionality.