Microscopic mechanisms of graphene electrolytic delamination from metal substrates

In this paper, hydrogen bubbling delamination of graphene (Gr) from copper using a strong electrolyte (KOH) water solution was performed, focusing on the effect of the KOH concentration (C_KOH) on the Gr delamination rate. A factor of ∼10 decrease in the time required for the complete Gr delamination from Cu cathodes with the same geometry was found increasing C_KOH from ∼0.05 M to ∼0.60 M. After transfer of the separated Gr membranes to SiO₂ substrates by a highly reproducible thermo-compression printing method, an accurate atomic force microscopy investigation of the changes in Gr morphology as a function of C_KOH was performed. Supported by these analyses, a microscopic model of the delamination process has been proposed, where a key role is played by graphene wrinkles acting as nucleation sites for H₂ bubbles at the cathode perimeter. With this approach, the H₂ supersaturation generated at the electrode for different electrolyte concentrations was estimated and the inverse dependence of t_d on C_KOH was quantitatively explained. Although developed in the case of Cu, this analysis is generally valid and can be applied to describe the electrolytic delamination of graphene from several metal substrates.