Rectification and Amplification of Ionic Current in Planar Graphene/Graphene-Oxide Junctions: An Electrochemical Diode and Transistor

This manuscript describes the fabrication of a two-dimensional planar junction formed with graphene oxide (GO) and selective electrochemically reduced graphene oxides (ERGOs), which exhibits rectification of ionic current in the presence of electrolyte. Moreover, amplification of the ionic current has also been demonstrated in planar transistor configuration constituted with two back-to-back planar GO–ERGO junctions. Structural modification-induced change in the electronic property of ERGO samples compared to GO is observed, and Mott–Schottky analysis confirms that the GO and ERGO are of n-type and p-type conductivities, respectively, which determine interfacial charge transfer from either electrode to electrolyte or vice versa. Thus, the ionic current is controlled by the modulation of the interfacial charge concentration by external voltage applied across the junction sample. Hence, this device exhibits bias-dependent unidirectional ion current, presumably through electrochemical oxidation of OH^– ions on ERGO (p side) and reduction of H⁺ ions on GO (n side) interface, which confirms the formation of an electrochemical p–n junction diode