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.