Highly efficient carbonization of nanocellulose to biocarbon aerogels with ultrahigh light absorption efficiency and evaporation rate as bifunctional solar/electric driven steam generator for water purification

Solar photo-thermal materials can be used to prepare fresh water in a green, economical and environmentally friendly way and have great potential for applications in solving the world's freshwater crisis. Here, by carbonizing nanocellulose aerogels , the obtained cellulose nanofiber crosslinked vinyltrimethoxysilane carbon aerogels (CVCAs) have a reticulated three-dimensional structure, high electrical conductivity (0.79 S/m) and low thermal conductivity(0.32 W/mK). Polypyrrole (PPy) coated on CVCAs (CVCAs-P) imparted its hydrophilicity and excellent electrical conductivity (1.95 S/m). CVCAs-P showed excellent performance in the field of interfacial evaporation due to its three-dimensional reticular structure, and low thermal conductivity , which gave a high light absorption (94%–97%) and an apparent water evaporation performance of 1.54 kg m −2  h −1 under 1 sun. Moreover, CVCAs-P with good electrical conductivity can be used for electro-thermal conversion using an external power supply, allowing for electrically driven water evaporation at night. This work solves the problem of conventional interfacial evaporation materials being overly dependent on sunlight.