The preparation of graphene foam by one-step reduction and air-drying for oil–water separation

The freeze-drying or supercritical CO 2 drying methods are usually used to remove the solvent to keep the shape of material in traditional methods for preparing graphene foam. Porous frozen tofu is a kind of traditional Chinese food and prepared through a process of freezing casting and thawing. Inspired by it, a green and economic approach for graphene foam (GF) synthesis using one-step reduction and air-drying is reported in this article. By controlling the reduction time and precursor concentration, monolithic GF with a little or without volume shrinkage can be obtained after a simple pre-freezing, thawing, and air-drying step of the graphene hydrogel. The obtained GF shows low density (17.5 mg/cm 3 ), superelastic, high recyclability, and excellent oil absorption ability. During the whole preparation process, the conditions were mild, and no special equipment such as freezer dryer was used, which is beneficial to large-scale production of porous GF with high oil adsorption and recyclability. One-step green reduction and air-drying method was used to synthesis graphene foam and it exhibited excellent oil–water separation ability.