Edge Exposure and Electrochemical Modulation of Graphene Oxide by Focused Cu Ion Bombardment

The modification of graphene oxide by energetic ion beams offers a promising alternative to conventional reduction techniques, providing spatially controlled tuning of the structural and electrochemical properties. In this study, we investigate the effect of focused Cu ion beam irradiation on free-standing graphene oxide foils using a comprehensive suite of characterization methods, including scanning electron microscopy, energy-dispersive spectroscopy, Raman spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and scanning electrochemical microscopy. Cu ion bombardment was found to induce partial reduction of graphene oxide, evidenced by a decrease in oxygen content, an increased C/O ratio, and enhancement of graphitic carbon features. Scanning electrochemical microscopy measurements using the [Ru(NH₃)₆]³⁺ redox probe revealed significantly enhanced electrochemical activity in and around the irradiated regions. This enhancement is likely influenced by local thinning of the graphene oxide layer and the increased exposure of reactive edge regions generated during irradiation rather than adsorption effects being the dominant factor. Elemental mapping confirmed a depletion of the Ru signal within bombarded stripes, supporting the structural origin of activity enhancement. These findings establish Cu-ion irradiation as a reagent-free, maskless approach for nanoscale patterning of electrochemically active regions in graphene oxide, with potential applications in sensing, catalysis, and electronic devices.