Synthesis of a high-temperature stable electrochemically exfoliated graphene

A new and facile electrochemical exfoliation approach is proposed to produce better quality electrochemically exfoliated graphene with excellent high-temperature stability. The method is based on graphene exfoliation in inorganic electrolytes (e.g. (NH4)2HPO4 and (NH4)2SO4 and different combinations of these salts) where the electrolyte composition was found to have a significant impact on the yield, morphology, structure, and high-temperature stability of the graphene sheets. The graphene prepared using (NH4)2HPO4 electrolyte showed the lowest level of defects in comparison to the other electrochemically exfoliated graphene and an exceptional high-temperature stability in air, at temperatures of up to 750 °C; much higher than typical high surface area carbon materials which are unstable around 400 °C–500 °C in air. The addition of (NH4)2SO4 to the (NH4)2HPO4 electrolyte improved the exfoliation process and increased the production of single layer graphene sheets from 19% to ∼50%. These hybrid electrolytes also led to nitrogen, phosphorus, and sulphur tri-doped graphene sheets with a fewer defects and high-temperature stability in air. This simple process offers a promising approach for large scale preparation of doped graphene with fewer defects and exceptional properties for various applications. [Display omitted]