Electrochemical Behavior of Graphene in a Deep Eutectic Solvent.

Graphene electrodes and deep eutectic solvents (DESs) are two emerging material systems that have individually shown highly promising properties in electrochemical applications. To date, however, it has not been tested whether the combination of graphene and DESs can yield synergistic effects in electrochemistry. We therefore study the electrochemical behavior of a defined graphene monolayer of centimeter-scale, which was produced by chemical vapor deposition and transferred onto insulating SiO2/Si supports, in the common DES choline chloride/ethylene glycol (12CE) under typical electrochemical conditions. We measure the graphene potential window in 12CE and estimate the apparent electron transfer kinetics of an outer-sphere redox couple. We further explore the applicability of the 12CE electrolyte to fabricate nanostructured metal (Zn) and metalloid (Ge) hybrids with graphene by electrodeposition. By comparing our graphene electrodes with common bulk glassy carbon electrodes, a key finding we make is that the two-dimensional nature of the graphene electrodes has a clear impact on DES-based electrochemistry. Thereby, we provide a first framework toward rational optimization of graphene-DES systems for electrochemical applications.