Fine-tuning the functionality of reduced graphene oxide via bipolar electrochemistry in freestanding 2D reaction layers

Graphene has unique characteristics that are appealing for energy-related applications such as ultra-lightweight and high surface-area/electrical-conductivity. However, generating functional graphene sheets is still a very challenging task. Here, a novel approach based on an original bipolar electrochemistry set-up, using a quasi-2D reaction layer, is suggested, which allows a precise control of dispersibility and conductivity of graphene sheets. In this system, a freestanding 2D layer of aqueous solution, containing 2D graphene oxide (GO) sheets, is placed between two platinum feeder electrodes, which are used to apply an electric field. As a result, the GO sheets experience a sufficiently high polarization to cause their transformation into reduced GO (rGO). The degree of reduction can be readily controlled by the field strength and exposure time, resulting in a wide range of rGO with different conductivity/dispersibility features. The partially reduced GO (prGO) sheets with engineered conductivity/dispersibility are used to prepare aqueous composites with a redox-polymer for organic battery applications. Additionally, at higher potentials, Pt nanoparticles are released from the feeder electrodes and attached to rGO sheets. The sheets were used for catalyzing hydrogen evolution reaction with a performance comparable to bulk Pt.