Continuous Graphene-like Layers Formed on Copper Substrates by Graphene Oxide Self-Assembly and Reduction

Copper substrates are known to be able to assist the spontaneous assembly and reduction of graphene oxide in liquid medium, but very scarce information is known about the involved mechanism. This study analyzes a number of relevant factors affecting this process: copper substrate geometry, concentration of graphene oxide dispersion, reaction time, presence of ligands in the reaction medium, and reaction temperature. Characterization techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and attenuated total reflectance-Fourier transformed infrared (ATR-FTIR) have been applied to characterize the reduced graphene oxide (rGO) coating on copper. In the light of the obtained results, a reaction mechanism is proposed. Open-area copper substrates favor not only the complete coating of the copper surface but also the formation of self-standing continuous rGO films on open areas. Removal of copper ions, which are originated in the redox process, takes place by means of Cu2+-rich subsurface streams flowing underneath the rGO layers toward the aqueous medium. This simple and cost-effective procedure paves the way to design graphene-like bidimensional layered structures from the copper-induced self-organization of GO platelets as building blocks.