Ionic permeability and interfacial doping of graphene on SiO2 measured with Terahertz photoconductivity measurements

Graphene has been widely used in various electrochemical applications owing to its outstanding electrical and chemical properties. The presence of electrolyte at the graphene surfaces affects graphene’s electronic properties, especially its electrical conductivity. The precise mechanism underlying the graphene-electrolyte interaction has remained elusive, despite the importance of graphene for electrochemical applications. Here, we employ optical-pump THz-probe spectroscopy as a contact-free and all-optical means to investigate the impact of cations on graphene conductivity in the electrolyte. We reveal ionic permeability though graphene, resulting in an interfacial doping effect in SiO2-supported graphene.