Ultrafast reduction of graphene oxide with Zn powder in neutral and alkaline solutions at room temperature promoted by the formation of metal complexes

Abstract

Graphene has been attracting strong attention due to its interesting structure and properties and important applications in many areas. The process of the oxidation of graphite into graphene oxide (GO) and the subsequent reduction of GO into graphene is regarded as an effective process to produce graphene on a large scale. The quality of the reduced GO is strongly dependent on the reduction method. This paper reports the reduction of GO with Zn powder in neutral and alkaline aqueous solutions at room temperature. The reducing capability of Zn powder can be significantly improved through the complex formation of Zn²⁺ with other species in solution, which greatly lowers the Zn²⁺ concentration. Ethylenediaminetetraacetic acid (EDTA) can form an Zn–EDTA²⁻ complex with Zn²⁺ and it is used for the reduction of GO by Zn in a neutral solution. The complex formation gives rise to quite low Zn²⁺ concentrations in solution. This effectively lowers the reduction potential of Zn/Zn²⁺ and enables the reduction of GO in neutral solutions. GO can be effectively reduced by Zn powder in alkaline solutions without EDTA as well. This is attributed to the complex formation of Zn²⁺ with OH⁻, where Zn²⁺ + 4OH⁻→ Zn(OH)₄²⁻. The reduced GO produced by these methods has high quality. Their C/O ratios for products obtained through GO reductions in neutral and alkaline solutions are 33.0 and 31.2 and their conductivities are 142 and 135 S cm⁻¹, respectively.