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

Abstract

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°), while the under surface displayed a continuous membrane structure possessing rich wrinkles with superhydrophilicity (water contact angle < 5°). 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 m2/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.