Electrochemical reactivity of graphene under mechanical strain†

The electrochemical reaction of graphene with aryl diazonium molecules is recognized as an effective method for surface functionalization of graphene. As the charge-transfer rate between graphene and the diazonium molecules determines the degree of functionalization, considerable research has been dedicated to understanding the factors that influence this metric. Among them, the mechanical strain in graphene is particularly crucial because mechanical deformation is inevitable in flexible devices. The mechanical strain in graphene is predicted to generate a pseudo-scalar potential that shifts the energy of the Dirac point, but its influence on the electrochemical reactivity of graphene has been largely overlooked. In this study, we investigate the effect of mechanical strain on the electrochemical reactivity of graphene with 4-nitrobenzenediazonium tetrafluoroborate using a combination of experimental techniques and theoretical modeling. Our results reveal that the electrochemical reactivity of graphene initially decreases with strain but increases as the strain continues to increase. This behavior is explained by the Marcus–Gerischer theory, which accounts for the strain-induced shifts in the electronic density of states of graphene and the resulting changes in the electron transfer rate.