Electrolyte gating in graphene-based supercapacitors and its use for probing nanoconfined charging dynamics

The electronic conductivity of graphene-based porous electrodes can be modulated by their ionic charging state in supercapacitors, enabling a new in operando technique to probe the charging dynamics of electrical double layers under nanoconfinement. Graphene-based nanoporous materials have been extensively explored as high-capacity ion electrosorption electrodes for supercapacitors. However, little attention has been paid to exploiting the interactions between electrons that reside in the graphene lattice and the ions adsorbed between the individual graphene sheets. Here we report that the electronic conductance of a multilayered reduced graphene oxide membrane, when used as a supercapacitor electrode, can be modulated by the ionic charging state of the membrane, which gives rise to a collective electrolyte gating effect. This gating effect provides an in-operando approach for probing the charging dynamics of supercapacitors electrically. Using this approach, we observed a pore-size-dependent ionic hysteresis or memory effect in reduced graphene oxide membranes when the interlayer distance is comparable to the ion diameter. Our results may stimulate the design of novel devices based on the ion-electron interactions under nanoconfinement.