Improved interfacial floatability of superhydrophobic and compressive S, N co-doped graphene aerogel by electrostatic spraying for highly efficient organic pollutants recovery from water

Sulfur and nitrogen co-doped graphene aerogel with Janus wettability of superhydrophobic/superhydrophilic was prepared with hydrothermal reduction combined with electrostatic spraying method. The upper surface exhibited an interconnected and porous 3D network with superhydrophobic property (water contact angle > 150 degrees), while the under surface displayed a continuous membrane structure possessing rich wrinkles with superhydrophilicity (water contact angle < 5 degrees). The hydrophobic mechanism was further demonstrated by FT-IR, XPS and theoretical calculations, resulting from the oxygen-containing functional groups decrease and the changes of surface electrostatic potentials and charge densities due to S, N co-doping into the graphitic network. More importantly, the Janus superwettability of the graphene aerogel enables it to stabilize at multiple interfaces, such as air/water, air/hexane, hexane/water and water/CCl4 interfaces, resolving the floating problem under windy conditions for the ultralight and hydrophobic materials, which is vital for the practical applications. The as-synthesized graphene aerogel also exhibits remarkable compressibility with full recovery even at 90% strain, and remains over 50% of maximum stress even after 1000 cycles at 90% strain. With high BET surface area (406.80 m(2)/g), high compressibility and robust structure, our graphene aerogel shows fast adsorption with high capacity and excellent recyclable performance, achieving up to about 65-192 times of its own weight for various oils and organic solvents.