Investigating the Integrity of Graphene towards the Electrochemical Oxygen Evolution Reaction

Mono-, few- and multi- layer graphene is explored towards the electrochemical Oxygen Evolution Reaction (OER). Raman mapping characterisation is performed, revealing that the structure of basal plane graphene is damaged due to the electrochemical perturbation of the OER. Electrochemical perturbation, in the form of electrochemical potential scanning (linear sweep voltammetry), and a thorough comparison of the OER at different scan rates and chronoamperometry tests at different voltages, create active edge plane sites/defects upon the basal plane graphene surface in the case of the mono- and few- layer graphene electrodes. The electrochemical performance gradually decreases with consecutive OER scans upon a given graphene electrode, with the process damaging the basal plane graphene sheet, after which there is a loss in the electrochemical signal due to a loss in electrically conductive pathways. Importantly, the severity of these changes is dependent on the potential and chosen scan rate that is applied to the graphene electrode. In contrast, however, multilayer graphene's initial performance towards the OER process improves after the first few scans, which is likely due to an increase in the coverage of edge plane sites/defects and its underlying layers maintaining electrical contact. This work indicates the importance of the scan rate and potential limits applied to graphene electrodes in addition to the relationship between the number of layers and structural integrity. This new knowledge is of fundamental importance to be advantageously applied within the energy sector and beyond.